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Date:   Sun, 15 May 2022 20:38:14 +0800
From:   Huacai Chen <chenhuacai@...il.com>
To:     WANG Xuerui <kernel@...0n.name>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Airlie <airlied@...ux.ie>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        linux-efi <linux-efi@...r.kernel.org>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH V10 09/22] LoongArch: Add boot and setup routines

Hi, Xuerui,

On Sun, May 15, 2022 at 4:45 PM WANG Xuerui <kernel@...0n.name> wrote:
>
> Hi,
>
> On 5/14/22 16:03, Huacai Chen wrote:
> > Add basic boot, setup and reset routines for LoongArchi support.
>
> typo -- "LoongArchi".
>
> This sentence could just be "Add basic boot, setup and reset routines
> for LoongArch".
>
> > LoongArch uses UEFI-based firmware. The firmware uses ACPI and DMI/
> > SMBIOS to pass configuration information to the Linux kernel.
> "The firmware passes configuration information to the kernel via ACPI
> and DMI/SMBIOS."
> >
> > Now the boot information passed to kernel is like this:
> > 1, kernel get 2 register values (a0 and a1) from bootloader.
> > 2, a0 is a "efi boot flag" to distinguish UEFI BIOS and non-UEFI BIOS.
> > 3, a1 is a "fdt pointer", including systable, memmap, cmdline and initrd
> >     information.
>
> This paragraph is hopelessly Chinglish, let me reword a bit:
>
> Currently an ad-hoc interface between the kernel and the bootloader is
> implemented. Kernel gets 2 values from the bootloader, passed in
> registers a0 and a1; a0 is an "EFI boot flag" distinguishing UEFI and
> non-UEFI firmware, while a1 is a pointer to an FDT with systable,
> memmap, cmdline and initrd information.
>
> >
> > The above interface is an internal interface between bootloader (grub,
> > efistub, etc.) and the raw kernel. You can use this method to boot the
> > Linux kernel in raw elf format, but it is recommend to use the standard
> > UEFI boot protocol (efistub).
> This interface is used by existing bootloaders for booting kernels in
> raw ELF format. However, the standard UEFI boot protocol (EFISTUB) is
> preferred down the road.
Thank you for helping me to improve the words.

> >
> > ECR for adding LoongArch support in ACPI:
> > https://mantis.uefi.org/mantis/view.php?id=2203
> >
> > ECR for adding LoongArch support in ACPI (version update):
> > https://mantis.uefi.org/mantis/view.php?id=2268
> >
> > ECR for adding LoongArch support in UEFI:
> > https://mantis.uefi.org/mantis/view.php?id=2313
> >
> > ACPI changes of LoongArch have been approved in the last year, but the
> > new version of ACPI SPEC hasn't been made public yet. And UEFI changes
> > of LoongArch are under review now.
> >
> > Cc: linux-efi@...r.kernel.org
> > Cc: Ard Biesheuvel <ardb@...nel.org>
> > Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> > ---
> >   arch/loongarch/include/asm/acenv.h            |  17 +
> >   arch/loongarch/include/asm/acpi.h             |  38 ++
> >   arch/loongarch/include/asm/bootinfo.h         |  41 +++
> >   arch/loongarch/include/asm/dmi.h              |  24 ++
> >   arch/loongarch/include/asm/efi.h              |  41 +++
> >   arch/loongarch/include/asm/reboot.h           |  10 +
> >   arch/loongarch/include/asm/setup.h            |  21 ++
> >   arch/loongarch/kernel/acpi.c                  | 338 +++++++++++++++++
> >   arch/loongarch/kernel/cacheinfo.c             | 122 ++++++
> >   arch/loongarch/kernel/cpu-probe.c             | 292 +++++++++++++++
> >   arch/loongarch/kernel/efi-header.S            | 100 +++++
> >   arch/loongarch/kernel/efi.c                   | 229 ++++++++++++
> >   arch/loongarch/kernel/env.c                   |  70 ++++
> >   arch/loongarch/kernel/head.S                  |  97 +++++
> >   arch/loongarch/kernel/image-vars.h            |  29 ++
> >   arch/loongarch/kernel/mem.c                   |  64 ++++
> >   arch/loongarch/kernel/reset.c                 |  90 +++++
> >   arch/loongarch/kernel/setup.c                 | 348 ++++++++++++++++++
> >   arch/loongarch/kernel/time.c                  | 220 +++++++++++
> >   arch/loongarch/kernel/topology.c              |  13 +
> >   drivers/firmware/efi/Kconfig                  |   2 +-
> >   drivers/firmware/efi/libstub/Makefile         |  10 +
> >   .../firmware/efi/libstub/efi-stub-helper.c    |   2 +-
> >   drivers/firmware/efi/libstub/efi-stub.c       |   2 +-
> >   drivers/firmware/efi/libstub/loongarch-stub.c |  87 +++++
> >   include/linux/efi.h                           |   1 +
> >   include/linux/pe.h                            |   1 +
> >   27 files changed, 2306 insertions(+), 3 deletions(-)
> >   create mode 100644 arch/loongarch/include/asm/acenv.h
> >   create mode 100644 arch/loongarch/include/asm/acpi.h
> >   create mode 100644 arch/loongarch/include/asm/bootinfo.h
> >   create mode 100644 arch/loongarch/include/asm/dmi.h
> >   create mode 100644 arch/loongarch/include/asm/efi.h
> >   create mode 100644 arch/loongarch/include/asm/reboot.h
> >   create mode 100644 arch/loongarch/include/asm/setup.h
> >   create mode 100644 arch/loongarch/kernel/acpi.c
> >   create mode 100644 arch/loongarch/kernel/cacheinfo.c
> >   create mode 100644 arch/loongarch/kernel/cpu-probe.c
> >   create mode 100644 arch/loongarch/kernel/efi-header.S
> >   create mode 100644 arch/loongarch/kernel/efi.c
> >   create mode 100644 arch/loongarch/kernel/env.c
> >   create mode 100644 arch/loongarch/kernel/head.S
> >   create mode 100644 arch/loongarch/kernel/image-vars.h
> >   create mode 100644 arch/loongarch/kernel/mem.c
> >   create mode 100644 arch/loongarch/kernel/reset.c
> >   create mode 100644 arch/loongarch/kernel/setup.c
> >   create mode 100644 arch/loongarch/kernel/time.c
> >   create mode 100644 arch/loongarch/kernel/topology.c
> >   create mode 100644 drivers/firmware/efi/libstub/loongarch-stub.c
> >
> > diff --git a/arch/loongarch/include/asm/acenv.h b/arch/loongarch/include/asm/acenv.h
> > new file mode 100644
> > index 000000000000..290a15a41258
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/acenv.h
> > @@ -0,0 +1,17 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * LoongArch specific ACPICA environments and implementation
> > + *
> > + * Author: Jianmin Lv <lvjianmin@...ngson.cn>
> > + *         Huacai Chen <chenhuacai@...ngson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#ifndef _ASM_LOONGARCH_ACENV_H
> > +#define _ASM_LOONGARCH_ACENV_H
> > +
> > +/* The head file is required by ACPI core, but we have nothing to fill
> > + * it now, update it later when needed.
> > + */
> > +
> > +#endif /* _ASM_LOONGARCH_ACENV_H */
> > diff --git a/arch/loongarch/include/asm/acpi.h b/arch/loongarch/include/asm/acpi.h
> > new file mode 100644
> > index 000000000000..62044cd5b7bc
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/acpi.h
> > @@ -0,0 +1,38 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Author: Jianmin Lv <lvjianmin@...ngson.cn>
> > + *         Huacai Chen <chenhuacai@...ngson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#ifndef _ASM_LOONGARCH_ACPI_H
> > +#define _ASM_LOONGARCH_ACPI_H
> > +
> > +#ifdef CONFIG_ACPI
> > +extern int acpi_strict;
> > +extern int acpi_disabled;
> > +extern int acpi_pci_disabled;
> > +extern int acpi_noirq;
> > +
> > +#define acpi_os_ioremap acpi_os_ioremap
> > +void __init __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
> > +
> > +static inline void disable_acpi(void)
> > +{
> > +     acpi_disabled = 1;
> > +     acpi_pci_disabled = 1;
> > +     acpi_noirq = 1;
> > +}
> > +
> > +static inline bool acpi_has_cpu_in_madt(void)
> > +{
> > +     return true;
> > +}
> > +
> > +extern struct list_head acpi_wakeup_device_list;
> > +
> > +#endif /* !CONFIG_ACPI */
> > +
> > +#define ACPI_TABLE_UPGRADE_MAX_PHYS ARCH_LOW_ADDRESS_LIMIT
> > +
> > +#endif /* _ASM_LOONGARCH_ACPI_H */
> > diff --git a/arch/loongarch/include/asm/bootinfo.h b/arch/loongarch/include/asm/bootinfo.h
> > new file mode 100644
> > index 000000000000..0076a9e1a817
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/bootinfo.h
> > @@ -0,0 +1,41 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#ifndef _ASM_BOOTINFO_H
> > +#define _ASM_BOOTINFO_H
> > +
> > +#include <linux/types.h>
> > +#include <asm/setup.h>
> > +
> > +const char *get_system_type(void);
> > +
> > +extern void init_environ(void);
> > +extern void memblock_init(void);
> > +extern void platform_init(void);
> > +
> > +struct loongson_board_info {
> > +     int bios_size;
> > +     char *bios_vendor;
> > +     char *bios_version;
> > +     char *bios_release_date;
> > +     char *board_name;
> > +     char *board_vendor;
> > +};
> > +
> > +struct loongson_system_configuration {
> > +     int nr_cpus;
> > +     int nr_nodes;
> > +     int nr_io_pics;
> > +     int boot_cpu_id;
> > +     int cores_per_node;
> > +     int cores_per_package;
> > +     char *cpuname;
> > +};
> > +
> > +extern u64 efi_system_table;
> > +extern struct loongson_board_info b_info;
> > +extern struct loongson_system_configuration loongson_sysconf;
> > +extern unsigned long fw_arg0, fw_arg1, fw_arg2;
> > +
> > +#endif /* _ASM_BOOTINFO_H */
> > diff --git a/arch/loongarch/include/asm/dmi.h b/arch/loongarch/include/asm/dmi.h
> > new file mode 100644
> > index 000000000000..605493417753
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/dmi.h
> > @@ -0,0 +1,24 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#ifndef _ASM_DMI_H
> > +#define _ASM_DMI_H
> > +
> > +#include <linux/io.h>
> > +#include <linux/memblock.h>
> > +
> > +#define dmi_early_remap(x, l)        dmi_remap(x, l)
> > +#define dmi_early_unmap(x, l)        dmi_unmap(x)
> > +#define dmi_alloc(l)         memblock_alloc(l, PAGE_SIZE)
> > +
> > +static inline void *dmi_remap(u64 phys_addr, unsigned long size)
> > +{
> > +     return ((void *)TO_CACHE(phys_addr));
> > +}
> > +
> > +static inline void dmi_unmap(void *addr)
> > +{
> > +}
> > +
> > +#endif /* _ASM_DMI_H */
> > diff --git a/arch/loongarch/include/asm/efi.h b/arch/loongarch/include/asm/efi.h
> > new file mode 100644
> > index 000000000000..319c50ac8b33
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/efi.h
> > @@ -0,0 +1,41 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#ifndef _ASM_LOONGARCH_EFI_H
> > +#define _ASM_LOONGARCH_EFI_H
> > +
> > +#include <linux/efi.h>
> > +
> > +void __init efi_init(void);
> > +void __init efi_runtime_init(void);
> > +void efifb_setup_from_dmi(struct screen_info *si, const char *opt);
> > +
> > +#define ARCH_EFI_IRQ_FLAGS_MASK  0x00000001  /*bit0: CP0 Status.IE*/
>
> Stray MIPS-ism that is wrong for LoongArch as well. This needs to refer
> to CSR.CRMD.IE which is the bit 2:
>
> #define ARCH_EFI_IRQ_FLAGS_MASK  0x00000004  /* bit 2: CSR.CRMD.IE */
OK, thanks, this is my mistake.

>
> > +
> > +#define arch_efi_call_virt_setup()               \
> > +({                                               \
> > +})
> > +
> > +#define arch_efi_call_virt(p, f, args...)        \
> > +({                                               \
> > +     efi_##f##_t * __f;                       \
> > +     __f = p->f;                              \
> > +     __f(args);                               \
> > +})
> > +
> > +#define arch_efi_call_virt_teardown()            \
> > +({                                               \
> > +})
> > +
> > +#define EFI_ALLOC_ALIGN              SZ_64K
> > +
> > +struct screen_info *alloc_screen_info(void);
> > +void free_screen_info(struct screen_info *si);
> > +
> > +static inline unsigned long efi_get_max_initrd_addr(unsigned long image_addr)
> > +{
> > +     return ULONG_MAX;
> > +}
> > +
> > +#endif /* _ASM_LOONGARCH_EFI_H */
> > diff --git a/arch/loongarch/include/asm/reboot.h b/arch/loongarch/include/asm/reboot.h
> > new file mode 100644
> > index 000000000000..51151749d8f0
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/reboot.h
> > @@ -0,0 +1,10 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#ifndef _ASM_REBOOT_H
> > +#define _ASM_REBOOT_H
> > +
> > +extern void (*pm_restart)(void);
> > +
> > +#endif /* _ASM_REBOOT_H */
> > diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
> > new file mode 100644
> > index 000000000000..6d7d2a3e23dd
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/setup.h
> > @@ -0,0 +1,21 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#ifndef _LOONGARCH_SETUP_H
> > +#define _LOONGARCH_SETUP_H
> > +
> > +#include <linux/types.h>
> > +#include <uapi/asm/setup.h>
> > +
> > +#define VECSIZE 0x200
> > +
> > +extern unsigned long eentry;
> > +extern unsigned long tlbrentry;
> > +extern void cpu_cache_init(void);
> > +extern void per_cpu_trap_init(int cpu);
> > +extern void set_handler(unsigned long offset, void *addr, unsigned long len);
> > +extern void set_merr_handler(unsigned long offset, void *addr, unsigned long len);
> > +
> > +#endif /* __SETUP_H */
> > diff --git a/arch/loongarch/kernel/acpi.c b/arch/loongarch/kernel/acpi.c
> > new file mode 100644
> > index 000000000000..506ab9912c51
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/acpi.c
> > @@ -0,0 +1,338 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * acpi.c - Architecture-Specific Low-Level ACPI Boot Support
> > + *
> > + * Author: Jianmin Lv <lvjianmin@...ngson.cn>
> > + *         Huacai Chen <chenhuacai@...ngson.cn>
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <linux/init.h>
> > +#include <linux/acpi.h>
> > +#include <linux/irq.h>
> > +#include <linux/irqdomain.h>
> > +#include <linux/memblock.h>
> > +#include <linux/serial_core.h>
> > +#include <asm/io.h>
> > +#include <asm/loongson.h>
> > +
> > +int acpi_disabled;
> > +EXPORT_SYMBOL(acpi_disabled);
> > +int acpi_noirq;
> > +int acpi_pci_disabled;
> > +EXPORT_SYMBOL(acpi_pci_disabled);
> > +int acpi_strict = 1; /* We have no workarounds on LoongArch */
> > +int num_processors;
> > +int disabled_cpus;
> > +enum acpi_irq_model_id acpi_irq_model = ACPI_IRQ_MODEL_PLATFORM;
> > +
> > +u64 acpi_saved_sp;
> > +
> > +#define MAX_CORE_PIC 256
> > +
> > +#define PREFIX                       "ACPI: "
> > +
> > +int acpi_gsi_to_irq(u32 gsi, unsigned int *irqp)
> > +{
> > +     if (irqp != NULL)
> > +             *irqp = acpi_register_gsi(NULL, gsi, -1, -1);
> > +     return (*irqp >= 0) ? 0 : -EINVAL;
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
> > +
> > +int acpi_isa_irq_to_gsi(unsigned int isa_irq, u32 *gsi)
> > +{
> > +     if (gsi)
> > +             *gsi = isa_irq;
> > +     return 0;
> > +}
> > +
> > +/*
> > + * success: return IRQ number (>=0)
> > + * failure: return < 0
> > + */
> > +int acpi_register_gsi(struct device *dev, u32 gsi, int trigger, int polarity)
> > +{
> > +     int id;
> > +     struct irq_fwspec fwspec;
> > +
> > +     switch (gsi) {
> > +     case GSI_MIN_CPU_IRQ ... GSI_MAX_CPU_IRQ:
> > +             fwspec.fwnode = liointc_domain->fwnode;
> > +             fwspec.param[0] = gsi - GSI_MIN_CPU_IRQ;
> > +             fwspec.param_count = 1;
> > +
> > +             return irq_create_fwspec_mapping(&fwspec);
> > +
> > +     case GSI_MIN_LPC_IRQ ... GSI_MAX_LPC_IRQ:
> > +             if (!pch_lpc_domain)
> > +                     return -EINVAL;
> > +
> > +             fwspec.fwnode = pch_lpc_domain->fwnode;
> > +             fwspec.param[0] = gsi - GSI_MIN_LPC_IRQ;
> > +             fwspec.param[1] = acpi_dev_get_irq_type(trigger, polarity);
> > +             fwspec.param_count = 2;
> > +
> > +             return irq_create_fwspec_mapping(&fwspec);
> > +
> > +     case GSI_MIN_PCH_IRQ ... GSI_MAX_PCH_IRQ:
> > +             id = find_pch_pic(gsi);
> > +             if (id < 0)
> > +                     return -EINVAL;
> > +
> > +             fwspec.fwnode = pch_pic_domain[id]->fwnode;
> > +             fwspec.param[0] = gsi - acpi_pchpic[id]->gsi_base;
> > +             fwspec.param[1] = IRQ_TYPE_LEVEL_HIGH;
> > +             fwspec.param_count = 2;
> > +
> > +             return irq_create_fwspec_mapping(&fwspec);
> > +     }
> > +
> > +     return -EINVAL;
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_register_gsi);
> > +
> > +void acpi_unregister_gsi(u32 gsi)
> > +{
> > +
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_unregister_gsi);
> > +
> > +void __init __iomem * __acpi_map_table(unsigned long phys, unsigned long size)
> > +{
> > +
> > +     if (!phys || !size)
> > +             return NULL;
> > +
> > +     return early_memremap(phys, size);
> > +}
> > +void __init __acpi_unmap_table(void __iomem *map, unsigned long size)
> > +{
> > +     if (!map || !size)
> > +             return;
> > +
> > +     early_memunmap(map, size);
> > +}
> > +
> > +void __init __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
> > +{
> > +     if (!memblock_is_memory(phys))
> > +             return ioremap(phys, size);
> > +     else
> > +             return ioremap_cache(phys, size);
> > +}
> > +
> > +void __init acpi_boot_table_init(void)
> > +{
> > +     /*
> > +      * If acpi_disabled, bail out
> > +      */
> > +     if (acpi_disabled)
> > +             return;
> > +
> > +     /*
> > +      * Initialize the ACPI boot-time table parser.
> > +      */
> > +     if (acpi_table_init()) {
> > +             disable_acpi();
> > +             return;
> > +     }
> > +}
> > +
> > +static int __init
> > +acpi_parse_cpuintc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     struct acpi_madt_core_pic *processor = NULL;
> > +
> > +     processor = (struct acpi_madt_core_pic *)header;
> > +     if (BAD_MADT_ENTRY(processor, end))
> > +             return -EINVAL;
> > +
> > +     acpi_table_print_madt_entry(&header->common);
> > +
> > +     return 0;
> > +}
> > +
> > +static int __init
> > +acpi_parse_liointc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     struct acpi_madt_lio_pic *liointc = NULL;
> > +
> > +     liointc = (struct acpi_madt_lio_pic *)header;
> > +
> > +     if (BAD_MADT_ENTRY(liointc, end))
> > +             return -EINVAL;
> > +
> > +     acpi_liointc = liointc;
> > +
> > +     return 0;
> > +}
> > +
> > +static int __init
> > +acpi_parse_eiointc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     static int id = 0;
> > +     struct acpi_madt_eio_pic *eiointc = NULL;
> > +
> > +     eiointc = (struct acpi_madt_eio_pic *)header;
> > +
> > +     if (BAD_MADT_ENTRY(eiointc, end))
> > +             return -EINVAL;
> > +
> > +     acpi_eiointc[id++] = eiointc;
> > +     loongson_sysconf.nr_io_pics = id;
> > +
> > +     return 0;
> > +}
> > +
> > +static int __init
> > +acpi_parse_htintc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     struct acpi_madt_ht_pic *htintc = NULL;
> > +
> > +     htintc = (struct acpi_madt_ht_pic *)header;
> > +
> > +     if (BAD_MADT_ENTRY(htintc, end))
> > +             return -EINVAL;
> > +
> > +     acpi_htintc = htintc;
> > +     loongson_sysconf.nr_io_pics = 1;
> > +
> > +     return 0;
> > +}
> > +
> > +static int __init
> > +acpi_parse_pch_pic(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     static int id = 0;
> > +     struct acpi_madt_bio_pic *pchpic = NULL;
> > +
> > +     pchpic = (struct acpi_madt_bio_pic *)header;
> > +
> > +     if (BAD_MADT_ENTRY(pchpic, end))
> > +             return -EINVAL;
> > +
> > +     acpi_pchpic[id++] = pchpic;
> > +
> > +     return 0;
> > +}
> > +
> > +static int __init
> > +acpi_parse_pch_msi(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     static int id = 0;
> > +     struct acpi_madt_msi_pic *pchmsi = NULL;
> > +
> > +     pchmsi = (struct acpi_madt_msi_pic *)header;
> > +
> > +     if (BAD_MADT_ENTRY(pchmsi, end))
> > +             return -EINVAL;
> > +
> > +     acpi_pchmsi[id++] = pchmsi;
> > +
> > +     return 0;
> > +}
> > +
> > +static int __init
> > +acpi_parse_pch_lpc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +     struct acpi_madt_lpc_pic *pchlpc = NULL;
> > +
> > +     pchlpc = (struct acpi_madt_lpc_pic *)header;
> > +
> > +     if (BAD_MADT_ENTRY(pchlpc, end))
> > +             return -EINVAL;
> > +
> > +     acpi_pchlpc = pchlpc;
> > +
> > +     return 0;
> > +}
> > +
> > +static void __init acpi_process_madt(void)
> > +{
> > +     int error;
> > +
> > +     /* Parse MADT CPUINTC entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_CORE_PIC, acpi_parse_cpuintc, MAX_CORE_PIC);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (CPUINTC entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +
> > +     loongson_sysconf.nr_cpus = num_processors;
> > +
> > +     /* Parse MADT LIOINTC entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_LIO_PIC, acpi_parse_liointc, 1);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (LIOINTC entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +
> > +     /* Parse MADT EIOINTC entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_EIO_PIC, acpi_parse_eiointc, MAX_IO_PICS);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (EIOINTC entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +
> > +     /* Parse MADT HTVEC entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_HT_PIC, acpi_parse_htintc, 1);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (HTVEC entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +
> > +     /* Parse MADT PCHPIC entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_BIO_PIC, acpi_parse_pch_pic, MAX_IO_PICS);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (PCHPIC entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +
> > +     /* Parse MADT PCHMSI entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_MSI_PIC, acpi_parse_pch_msi, MAX_IO_PICS);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (PCHMSI entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +
> > +     /* Parse MADT PCHLPC entries */
> > +     error = acpi_table_parse_madt(ACPI_MADT_TYPE_LPC_PIC, acpi_parse_pch_lpc, 1);
> > +     if (error < 0) {
> > +             disable_acpi();
> > +             pr_err(PREFIX "Invalid BIOS MADT (PCHLPC entries), ACPI disabled\n");
> > +             return;
> > +     }
> > +}
> > +
> > +int __init acpi_boot_init(void)
> > +{
> > +     /*
> > +      * If acpi_disabled, bail out
> > +      */
> > +     if (acpi_disabled)
> > +             return -1;
> > +
> > +     loongson_sysconf.boot_cpu_id = read_csr_cpuid();
> > +
> > +     /*
> > +      * Process the Multiple APIC Description Table (MADT), if present
> > +      */
> > +     acpi_process_madt();
> > +
> > +     /* Do not enable ACPI SPCR console by default */
> > +     acpi_parse_spcr(earlycon_acpi_spcr_enable, false);
> > +
> > +     return 0;
> > +}
> > +
> > +void __init arch_reserve_mem_area(acpi_physical_address addr, size_t size)
> > +{
> > +     memblock_reserve(addr, size);
> > +}
> > diff --git a/arch/loongarch/kernel/cacheinfo.c b/arch/loongarch/kernel/cacheinfo.c
> > new file mode 100644
> > index 000000000000..8c9fe29e98f0
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/cacheinfo.c
> > @@ -0,0 +1,122 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * LoongArch cacheinfo support
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#include <linux/cacheinfo.h>
> > +
> > +/* Populates leaf and increments to next leaf */
> > +#define populate_cache(cache, leaf, c_level, c_type)         \
> > +do {                                                         \
> > +     leaf->type = c_type;                                    \
> > +     leaf->level = c_level;                                  \
> > +     leaf->coherency_line_size = c->cache.linesz;            \
> > +     leaf->number_of_sets = c->cache.sets;                   \
> > +     leaf->ways_of_associativity = c->cache.ways;            \
> > +     leaf->size = c->cache.linesz * c->cache.sets *          \
> > +             c->cache.ways;                                  \
> > +     leaf++;                                                 \
> > +} while (0)
> > +
> > +int init_cache_level(unsigned int cpu)
> > +{
> > +     struct cpuinfo_loongarch *c = &current_cpu_data;
> > +     struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> > +     int levels = 0, leaves = 0;
> > +
> > +     /*
> > +      * If Dcache is not set, we assume the cache structures
> > +      * are not properly initialized.
> > +      */
> > +     if (c->dcache.waysize)
> > +             levels += 1;
> > +     else
> > +             return -ENOENT;
> > +
> > +
> > +     leaves += (c->icache.waysize) ? 2 : 1;
> > +
> > +     if (c->vcache.waysize) {
> > +             levels++;
> > +             leaves++;
> > +     }
> > +
> > +     if (c->scache.waysize) {
> > +             levels++;
> > +             leaves++;
> > +     }
> > +
> > +     if (c->tcache.waysize) {
> > +             levels++;
> > +             leaves++;
> > +     }
> > +
> > +     this_cpu_ci->num_levels = levels;
> > +     this_cpu_ci->num_leaves = leaves;
> > +     return 0;
> > +}
> > +
> > +static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
> > +                                        struct cacheinfo *sib_leaf)
> > +{
> > +     return !((this_leaf->level == 1) || (this_leaf->level == 2));
> > +}
> > +
> > +static void cache_cpumap_setup(unsigned int cpu)
> > +{
> > +     struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> > +     struct cacheinfo *this_leaf, *sib_leaf;
> > +     unsigned int index;
> > +
> > +     for (index = 0; index < this_cpu_ci->num_leaves; index++) {
> > +             unsigned int i;
> > +
> > +             this_leaf = this_cpu_ci->info_list + index;
> > +             /* skip if shared_cpu_map is already populated */
> > +             if (!cpumask_empty(&this_leaf->shared_cpu_map))
> > +                     continue;
> > +
> > +             cpumask_set_cpu(cpu, &this_leaf->shared_cpu_map);
> > +             for_each_online_cpu(i) {
> > +                     struct cpu_cacheinfo *sib_cpu_ci = get_cpu_cacheinfo(i);
> > +
> > +                     if (i == cpu || !sib_cpu_ci->info_list)
> > +                             continue;/* skip if itself or no cacheinfo */
> > +                     sib_leaf = sib_cpu_ci->info_list + index;
> > +                     if (cache_leaves_are_shared(this_leaf, sib_leaf)) {
> > +                             cpumask_set_cpu(cpu, &sib_leaf->shared_cpu_map);
> > +                             cpumask_set_cpu(i, &this_leaf->shared_cpu_map);
> > +                     }
> > +             }
> > +     }
> > +}
> > +
> > +int populate_cache_leaves(unsigned int cpu)
> > +{
> > +     int level = 1;
> > +     struct cpuinfo_loongarch *c = &current_cpu_data;
> > +     struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> > +     struct cacheinfo *this_leaf = this_cpu_ci->info_list;
> > +
> > +     if (c->icache.waysize) {
> > +             populate_cache(dcache, this_leaf, level, CACHE_TYPE_DATA);
> > +             populate_cache(icache, this_leaf, level++, CACHE_TYPE_INST);
> > +     } else {
> > +             populate_cache(dcache, this_leaf, level++, CACHE_TYPE_UNIFIED);
> > +     }
> > +
> > +     if (c->vcache.waysize)
> > +             populate_cache(vcache, this_leaf, level++, CACHE_TYPE_UNIFIED);
> > +
> > +     if (c->scache.waysize)
> > +             populate_cache(scache, this_leaf, level++, CACHE_TYPE_UNIFIED);
> > +
> > +     if (c->tcache.waysize)
> > +             populate_cache(tcache, this_leaf, level++, CACHE_TYPE_UNIFIED);
> > +
> > +     cache_cpumap_setup(cpu);
> > +     this_cpu_ci->cpu_map_populated = true;
> > +
> > +     return 0;
> > +}
> > diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
> > new file mode 100644
> > index 000000000000..ad1c4cde0dd6
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/cpu-probe.c
> > @@ -0,0 +1,292 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Processor capabilities determination functions.
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/ptrace.h>
> > +#include <linux/smp.h>
> > +#include <linux/stddef.h>
> > +#include <linux/export.h>
> > +#include <linux/printk.h>
> > +#include <linux/uaccess.h>
> > +
> > +#include <asm/cpu-features.h>
> > +#include <asm/elf.h>
> > +#include <asm/fpu.h>
> > +#include <asm/loongarch.h>
> > +#include <asm/pgtable-bits.h>
> > +#include <asm/setup.h>
> > +
> > +/* Hardware capabilities */
> > +unsigned int elf_hwcap __read_mostly;
> > +EXPORT_SYMBOL_GPL(elf_hwcap);
> > +
> > +/*
> > + * Determine the FCSR mask for FPU hardware.
> > + */
> > +static inline void cpu_set_fpu_fcsr_mask(struct cpuinfo_loongarch *c)
> > +{
> > +     unsigned long sr, mask, fcsr, fcsr0, fcsr1;
> > +
> > +     fcsr = c->fpu_csr0;
> > +     mask = FPU_CSR_ALL_X | FPU_CSR_ALL_E | FPU_CSR_ALL_S | FPU_CSR_RM;
> > +
> > +     sr = read_csr_euen();
> > +     enable_fpu();
> > +
> > +     fcsr0 = fcsr & mask;
> > +     write_fcsr(LOONGARCH_FCSR0, fcsr0);
> > +     fcsr0 = read_fcsr(LOONGARCH_FCSR0);
> > +
> > +     fcsr1 = fcsr | ~mask;
> > +     write_fcsr(LOONGARCH_FCSR0, fcsr1);
> > +     fcsr1 = read_fcsr(LOONGARCH_FCSR0);
> > +
> > +     write_fcsr(LOONGARCH_FCSR0, fcsr);
> > +
> > +     write_csr_euen(sr);
> > +
> > +     c->fpu_mask = ~(fcsr0 ^ fcsr1) & ~mask;
> > +}
> > +
> > +static inline void set_elf_platform(int cpu, const char *plat)
> > +{
> > +     if (cpu == 0)
> > +             __elf_platform = plat;
> > +}
> > +
> > +/* MAP BASE */
> > +unsigned long vm_map_base;
> > +EXPORT_SYMBOL_GPL(vm_map_base);
> > +
> > +static void cpu_probe_addrbits(struct cpuinfo_loongarch *c)
> > +{
> > +#ifdef __NEED_ADDRBITS_PROBE
> > +     c->pabits = (read_cpucfg(LOONGARCH_CPUCFG1) & CPUCFG1_PABITS) >> 4;
> > +     c->vabits = (read_cpucfg(LOONGARCH_CPUCFG1) & CPUCFG1_VABITS) >> 12;
> > +     vm_map_base = 0UL - (1UL << c->vabits);
> > +#endif
> > +}
> > +
> > +static void set_isa(struct cpuinfo_loongarch *c, unsigned int isa)
> > +{
> > +     switch (isa) {
> > +     case LOONGARCH_CPU_ISA_LA64:
> > +             c->isa_level |= LOONGARCH_CPU_ISA_LA64;
> > +             fallthrough;
> > +     case LOONGARCH_CPU_ISA_LA32S:
> > +             c->isa_level |= LOONGARCH_CPU_ISA_LA32S;
> > +             fallthrough;
> > +     case LOONGARCH_CPU_ISA_LA32R:
> > +             c->isa_level |= LOONGARCH_CPU_ISA_LA32R;
> > +             break;
> > +     }
> > +}
> > +
> > +static void cpu_probe_common(struct cpuinfo_loongarch *c)
> > +{
> > +     unsigned int config;
> > +     unsigned long asid_mask;
> > +
> > +     c->options = LOONGARCH_CPU_CPUCFG | LOONGARCH_CPU_CSR |
> > +                  LOONGARCH_CPU_TLB | LOONGARCH_CPU_VINT | LOONGARCH_CPU_WATCH;
> > +
> > +     elf_hwcap |= HWCAP_LOONGARCH_CRC32;
> > +
> > +     config = read_cpucfg(LOONGARCH_CPUCFG1);
> > +     if (config & CPUCFG1_UAL) {
> > +             c->options |= LOONGARCH_CPU_UAL;
> > +             elf_hwcap |= HWCAP_LOONGARCH_UAL;
> > +     }
> > +
> > +     config = read_cpucfg(LOONGARCH_CPUCFG2);
> > +     if (config & CPUCFG2_LAM) {
> > +             c->options |= LOONGARCH_CPU_LAM;
> > +             elf_hwcap |= HWCAP_LOONGARCH_LAM;
> > +     }
> > +     if (config & CPUCFG2_FP) {
> > +             c->options |= LOONGARCH_CPU_FPU;
> > +             elf_hwcap |= HWCAP_LOONGARCH_FPU;
> > +     }
> > +     if (config & CPUCFG2_COMPLEX) {
> > +             c->options |= LOONGARCH_CPU_COMPLEX;
> > +             elf_hwcap |= HWCAP_LOONGARCH_COMPLEX;
> > +     }
> > +     if (config & CPUCFG2_CRYPTO) {
> > +             c->options |= LOONGARCH_CPU_CRYPTO;
> > +             elf_hwcap |= HWCAP_LOONGARCH_CRYPTO;
> > +     }
> > +     if (config & CPUCFG2_LVZP) {
> > +             c->options |= LOONGARCH_CPU_LVZ;
> > +             elf_hwcap |= HWCAP_LOONGARCH_LVZ;
> > +     }
> > +
> > +     config = read_cpucfg(LOONGARCH_CPUCFG6);
> > +     if (config & CPUCFG6_PMP)
> > +             c->options |= LOONGARCH_CPU_PMP;
> > +
> > +     config = iocsr_readl(LOONGARCH_IOCSR_FEATURES);
> > +     if (config & IOCSRF_CSRIPI)
> > +             c->options |= LOONGARCH_CPU_CSRIPI;
> > +     if (config & IOCSRF_EXTIOI)
> > +             c->options |= LOONGARCH_CPU_EXTIOI;
> > +     if (config & IOCSRF_FREQSCALE)
> > +             c->options |= LOONGARCH_CPU_SCALEFREQ;
> > +     if (config & IOCSRF_FLATMODE)
> > +             c->options |= LOONGARCH_CPU_FLATMODE;
> > +     if (config & IOCSRF_EIODECODE)
> > +             c->options |= LOONGARCH_CPU_EIODECODE;
> > +     if (config & IOCSRF_VM)
> > +             c->options |= LOONGARCH_CPU_HYPERVISOR;
> > +
> > +     config = csr_readl(LOONGARCH_CSR_ASID);
> > +     config = (config & CSR_ASID_BIT) >> CSR_ASID_BIT_SHIFT;
> > +     asid_mask = GENMASK(config - 1, 0);
> > +     set_cpu_asid_mask(c, asid_mask);
> > +
> > +     config = read_csr_prcfg1();
> > +     c->kscratch_mask = GENMASK((config & CSR_CONF1_KSNUM) - 1, 0);
> > +     c->kscratch_mask &= ~(EXC_KSCRATCH_MASK | PERCPU_KSCRATCH_MASK | KVM_KSCRATCH_MASK);
> > +
> > +     config = read_csr_prcfg3();
> > +     switch (config & CSR_CONF3_TLBTYPE) {
> > +     case 0:
> > +             c->tlbsizemtlb = 0;
> > +             c->tlbsizestlbsets = 0;
> > +             c->tlbsizestlbways = 0;
> > +             c->tlbsize = 0;
> > +             break;
> > +     case 1:
> > +             c->tlbsizemtlb = ((config & CSR_CONF3_MTLBSIZE) >> CSR_CONF3_MTLBSIZE_SHIFT) + 1;
> > +             c->tlbsizestlbsets = 0;
> > +             c->tlbsizestlbways = 0;
> > +             c->tlbsize = c->tlbsizemtlb + c->tlbsizestlbsets * c->tlbsizestlbways;
> > +             break;
> > +     case 2:
> > +             c->tlbsizemtlb = ((config & CSR_CONF3_MTLBSIZE) >> CSR_CONF3_MTLBSIZE_SHIFT) + 1;
> > +             c->tlbsizestlbsets = 1 << ((config & CSR_CONF3_STLBIDX) >> CSR_CONF3_STLBIDX_SHIFT);
> > +             c->tlbsizestlbways = ((config & CSR_CONF3_STLBWAYS) >> CSR_CONF3_STLBWAYS_SHIFT) + 1;
> > +             c->tlbsize = c->tlbsizemtlb + c->tlbsizestlbsets * c->tlbsizestlbways;
> > +             break;
> > +     default:
> > +             pr_warn("Warning: unimplemented tlb type\n");
> > +     }
> > +}
> > +
> > +#define MAX_NAME_LEN 32
> > +#define VENDOR_OFFSET        0
> > +#define CPUNAME_OFFSET       9
> > +
> > +static char cpu_full_name[MAX_NAME_LEN] = "        -        ";
> > +
> > +static inline void cpu_probe_loongson(struct cpuinfo_loongarch *c, unsigned int cpu)
> > +{
> > +     uint64_t *vendor = (void *)(&cpu_full_name[VENDOR_OFFSET]);
> > +     uint64_t *cpuname = (void *)(&cpu_full_name[CPUNAME_OFFSET]);
> > +
> > +     __cpu_full_name[cpu] = cpu_full_name;
> > +     *vendor = iocsr_readq(LOONGARCH_IOCSR_VENDOR);
> > +     *cpuname = iocsr_readq(LOONGARCH_IOCSR_CPUNAME);
> > +
> > +     switch (c->processor_id & PRID_SERIES_MASK) {
> > +     case PRID_SERIES_LA132:
> > +             c->cputype = CPU_LOONGSON32;
> > +             set_isa(c, LOONGARCH_CPU_ISA_LA32S);
> > +             __cpu_family[cpu] = "Loongson-32bit";
> > +             pr_info("32-bit Loongson Processor probed (LA132 Core)\n");
> > +             break;
> > +     case PRID_SERIES_LA264:
> > +             c->cputype = CPU_LOONGSON64;
> > +             set_isa(c, LOONGARCH_CPU_ISA_LA64);
> > +             __cpu_family[cpu] = "Loongson-64bit";
> > +             pr_info("64-bit Loongson Processor probed (LA264 Core)\n");
> > +             break;
> > +     case PRID_SERIES_LA364:
> > +             c->cputype = CPU_LOONGSON64;
> > +             set_isa(c, LOONGARCH_CPU_ISA_LA64);
> > +             __cpu_family[cpu] = "Loongson-64bit";
> > +             pr_info("64-bit Loongson Processor probed (LA364 Core)\n");
> > +             break;
> > +     case PRID_SERIES_LA464:
> > +             c->cputype = CPU_LOONGSON64;
> > +             set_isa(c, LOONGARCH_CPU_ISA_LA64);
> > +             __cpu_family[cpu] = "Loongson-64bit";
> > +             pr_info("64-bit Loongson Processor probed (LA464 Core)\n");
> > +             break;
> > +     case PRID_SERIES_LA664:
> > +             c->cputype = CPU_LOONGSON64;
> > +             set_isa(c, LOONGARCH_CPU_ISA_LA64);
> > +             __cpu_family[cpu] = "Loongson-64bit";
> > +             pr_info("64-bit Loongson Processor probed (LA664 Core)\n");
> > +             break;
> > +     default: /* Default to 64 bit */
> > +             c->cputype = CPU_LOONGSON64;
> > +             set_isa(c, LOONGARCH_CPU_ISA_LA64);
> > +             __cpu_family[cpu] = "Loongson-64bit";
> > +             pr_info("64-bit Loongson Processor probed (Unknown Core)\n");
> > +     }
> > +}
> > +
> > +#ifdef CONFIG_64BIT
> > +/* For use by uaccess.h */
> > +u64 __ua_limit;
> > +EXPORT_SYMBOL(__ua_limit);
> > +#endif
> > +
> > +const char *__cpu_family[NR_CPUS];
> > +const char *__cpu_full_name[NR_CPUS];
> > +const char *__elf_platform;
> > +
> > +static void cpu_report(void)
> > +{
> > +     struct cpuinfo_loongarch *c = &current_cpu_data;
> > +
> > +     pr_info("CPU%d revision is: %08x (%s)\n",
> > +             smp_processor_id(), c->processor_id, cpu_family_string());
> > +     if (c->options & LOONGARCH_CPU_FPU)
> > +             pr_info("FPU%d revision is: %08x\n", smp_processor_id(), c->fpu_vers);
> > +}
> > +
> > +void cpu_probe(void)
> > +{
> > +     unsigned int cpu = smp_processor_id();
> > +     struct cpuinfo_loongarch *c = &current_cpu_data;
> > +
> > +     /*
> > +      * Set a default elf platform, cpu probe may later
> > +      * overwrite it with a more precise value
> > +      */
> > +     set_elf_platform(cpu, "loongarch");
> > +
> > +     c->cputype      = CPU_UNKNOWN;
> > +     c->processor_id = read_cpucfg(LOONGARCH_CPUCFG0);
> > +     c->fpu_vers     = (read_cpucfg(LOONGARCH_CPUCFG2) >> 3) & 0x3;
> > +
> > +     c->fpu_csr0     = FPU_CSR_RN;
> > +     c->fpu_mask     = FPU_CSR_RSVD;
> > +
> > +     cpu_probe_common(c);
> > +
> > +     per_cpu_trap_init(cpu);
> > +
> > +     switch (c->processor_id & PRID_COMP_MASK) {
> > +     case PRID_COMP_LOONGSON:
> > +             cpu_probe_loongson(c, cpu);
> > +             break;
> > +     }
> > +
> > +     BUG_ON(!__cpu_family[cpu]);
> > +     BUG_ON(c->cputype == CPU_UNKNOWN);
> > +
> > +     cpu_probe_addrbits(c);
> > +
> > +#ifdef CONFIG_64BIT
> > +     if (cpu == 0)
> > +             __ua_limit = ~((1ull << cpu_vabits) - 1);
> > +#endif
> > +
> > +     cpu_report();
> > +}
> > diff --git a/arch/loongarch/kernel/efi-header.S b/arch/loongarch/kernel/efi-header.S
> > new file mode 100644
> > index 000000000000..d299cac4e691
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/efi-header.S
> > @@ -0,0 +1,100 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <linux/pe.h>
> > +#include <linux/sizes.h>
> > +
> > +     .macro  __EFI_PE_HEADER
> > +     .long   PE_MAGIC
> > +.Lcoff_header:
> > +     .short  IMAGE_FILE_MACHINE_LOONGARCH            /* Machine */
> > +     .short  .Lsection_count                         /* NumberOfSections */
> > +     .long   0                                       /* TimeDateStamp */
> > +     .long   0                                       /* PointerToSymbolTable */
> > +     .long   0                                       /* NumberOfSymbols */
> > +     .short  .Lsection_table - .Loptional_header     /* SizeOfOptionalHeader */
> > +     .short  IMAGE_FILE_DEBUG_STRIPPED | \
> > +             IMAGE_FILE_EXECUTABLE_IMAGE | \
> > +             IMAGE_FILE_LINE_NUMS_STRIPPED           /* Characteristics */
> > +
> > +.Loptional_header:
> > +     .short  PE_OPT_MAGIC_PE32PLUS                   /* PE32+ format */
> > +     .byte   0x02                                    /* MajorLinkerVersion */
> > +     .byte   0x14                                    /* MinorLinkerVersion */
> > +     .long   __inittext_end - .Lefi_header_end       /* SizeOfCode */
> > +     .long   _end - __initdata_begin                 /* SizeOfInitializedData */
> > +     .long   0                                       /* SizeOfUninitializedData */
> > +     .long   __efistub_efi_pe_entry - _head          /* AddressOfEntryPoint */
> > +     .long   .Lefi_header_end - _head                /* BaseOfCode */
> > +
> > +.Lextra_header_fields:
> > +     .quad   0                                       /* ImageBase */
> > +     .long   PECOFF_SEGMENT_ALIGN                    /* SectionAlignment */
> > +     .long   PECOFF_FILE_ALIGN                       /* FileAlignment */
> > +     .short  0                                       /* MajorOperatingSystemVersion */
> > +     .short  0                                       /* MinorOperatingSystemVersion */
> > +     .short  LINUX_EFISTUB_MAJOR_VERSION             /* MajorImageVersion */
> > +     .short  LINUX_EFISTUB_MINOR_VERSION             /* MinorImageVersion */
> > +     .short  0                                       /* MajorSubsystemVersion */
> > +     .short  0                                       /* MinorSubsystemVersion */
> > +     .long   0                                       /* Win32VersionValue */
> > +
> > +     .long   _end - _head                            /* SizeOfImage */
> > +
> > +     /* Everything before the kernel image is considered part of the header */
> > +     .long   .Lefi_header_end - _head                /* SizeOfHeaders */
> > +     .long   0                                       /* CheckSum */
> > +     .short  IMAGE_SUBSYSTEM_EFI_APPLICATION         /* Subsystem */
> > +     .short  0                                       /* DllCharacteristics */
> > +     .quad   0                                       /* SizeOfStackReserve */
> > +     .quad   0                                       /* SizeOfStackCommit */
> > +     .quad   0                                       /* SizeOfHeapReserve */
> > +     .quad   0                                       /* SizeOfHeapCommit */
> > +     .long   0                                       /* LoaderFlags */
> > +     .long   (.Lsection_table - .) / 8               /* NumberOfRvaAndSizes */
> > +
> > +     .quad   0                                       /* ExportTable */
> > +     .quad   0                                       /* ImportTable */
> > +     .quad   0                                       /* ResourceTable */
> > +     .quad   0                                       /* ExceptionTable */
> > +     .quad   0                                       /* CertificationTable */
> > +     .quad   0                                       /* BaseRelocationTable */
> > +
> > +     /* Section table */
> > +.Lsection_table:
> > +     .ascii  ".text\0\0\0"
> > +     .long   __inittext_end - .Lefi_header_end       /* VirtualSize */
> > +     .long   .Lefi_header_end - _head                /* VirtualAddress */
> > +     .long   __inittext_end - .Lefi_header_end       /* SizeOfRawData */
> > +     .long   .Lefi_header_end - _head                /* PointerToRawData */
> > +
> > +     .long   0                                       /* PointerToRelocations */
> > +     .long   0                                       /* PointerToLineNumbers */
> > +     .short  0                                       /* NumberOfRelocations */
> > +     .short  0                                       /* NumberOfLineNumbers */
> > +     .long   IMAGE_SCN_CNT_CODE | \
> > +             IMAGE_SCN_MEM_READ | \
> > +             IMAGE_SCN_MEM_EXECUTE                   /* Characteristics */
> > +
> > +     .ascii  ".data\0\0\0"
> > +     .long   _end - __initdata_begin                 /* VirtualSize */
> > +     .long   __initdata_begin - _head                /* VirtualAddress */
> > +     .long   _edata - __initdata_begin               /* SizeOfRawData */
> > +     .long   __initdata_begin - _head                /* PointerToRawData */
> > +
> > +     .long   0                                       /* PointerToRelocations */
> > +     .long   0                                       /* PointerToLineNumbers */
> > +     .short  0                                       /* NumberOfRelocations */
> > +     .short  0                                       /* NumberOfLineNumbers */
> > +     .long   IMAGE_SCN_CNT_INITIALIZED_DATA | \
> > +             IMAGE_SCN_MEM_READ | \
> > +             IMAGE_SCN_MEM_WRITE                     /* Characteristics */
> > +
> > +     .org 0x20e
> > +     .word kernel_version - 512 -  _head
> > +
> > +     .set    .Lsection_count, (. - .Lsection_table) / 40
> > +.Lefi_header_end:
> > +     .endm
> > diff --git a/arch/loongarch/kernel/efi.c b/arch/loongarch/kernel/efi.c
> > new file mode 100644
> > index 000000000000..69ebdd4220ec
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/efi.c
> > @@ -0,0 +1,229 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * EFI initialization
> > + *
> > + * Author: Jianmin Lv <lvjianmin@...ngson.cn>
> > + *         Huacai Chen <chenhuacai@...ngson.cn>
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +
> > +#include <linux/acpi.h>
> > +#include <linux/efi.h>
> > +#include <linux/efi-bgrt.h>
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/export.h>
> > +#include <linux/io.h>
> > +#include <linux/kobject.h>
> > +#include <linux/memblock.h>
> > +#include <linux/reboot.h>
> > +#include <linux/uaccess.h>
> > +
> > +#include <asm/early_ioremap.h>
> > +#include <asm/efi.h>
> > +#include <asm/tlb.h>
> > +#include <asm/loongson.h>
> > +
> > +static unsigned long efi_nr_tables;
> > +static unsigned long efi_config_table;
> > +static unsigned long screen_info_table __initdata = EFI_INVALID_TABLE_ADDR;
> > +
> > +static efi_system_table_t *efi_systab;
> > +static efi_config_table_type_t arch_tables[] __initdata = {
> > +     {LINUX_EFI_LARCH_SCREEN_INFO_TABLE_GUID, &screen_info_table, "SINFO"},
> > +     {},
> > +};
> > +
> > +static void __init init_screen_info(void)
> > +{
> > +     struct screen_info *si;
> > +
> > +     if (screen_info_table == EFI_INVALID_TABLE_ADDR)
> > +             return;
> > +
> > +     si = early_memremap_ro(screen_info_table, sizeof(*si));
> > +     if (!si) {
> > +             pr_err("Could not map screen_info config table\n");
> > +             return;
> > +     }
> > +     screen_info = *si;
> > +     early_memunmap(si, sizeof(*si));
> > +
> > +     if (screen_info.orig_video_isVGA == VIDEO_TYPE_EFI)
> > +             memblock_reserve(screen_info.lfb_base, screen_info.lfb_size);
> > +}
> > +
> > +static void __init create_tlb(u32 index, u64 vppn, u32 ps, u32 mat)
> > +{
> > +     unsigned long tlblo0, tlblo1;
> > +
> > +     write_csr_pagesize(ps);
> > +
> > +     tlblo0 = vppn | CSR_TLBLO0_V | CSR_TLBLO0_WE |
> > +             CSR_TLBLO0_GLOBAL | (mat << CSR_TLBLO0_CCA_SHIFT);
> > +     tlblo1 = tlblo0 + (1 << ps);
> > +
> > +     csr_writeq(vppn, LOONGARCH_CSR_TLBEHI);
> > +     csr_writeq(tlblo0, LOONGARCH_CSR_TLBELO0);
> > +     csr_writeq(tlblo1, LOONGARCH_CSR_TLBELO1);
> > +     csr_xchgl(0, CSR_TLBIDX_EHINV, LOONGARCH_CSR_TLBIDX);
> > +     csr_xchgl(index, CSR_TLBIDX_IDX, LOONGARCH_CSR_TLBIDX);
> > +
> > +     tlb_write_indexed();
> > +}
> > +
> > +#define MTLB_ENTRY_INDEX     0x800
> > +
> > +/* Create VA == PA mapping as UEFI */
> > +static void __init fix_efi_mapping(void)
> > +{
> > +     unsigned int index = MTLB_ENTRY_INDEX;
> > +     unsigned int tlbnr = boot_cpu_data.tlbsizemtlb - 2;
> > +     unsigned long i, vppn;
> > +
> > +     /* Low Memory, Cached */
> > +     create_tlb(index++, 0x00000000, PS_128M, 1);
> > +     /* MMIO Registers, Uncached */
> > +     create_tlb(index++, 0x10000000, PS_128M, 0);
> > +
> > +     /* High Memory, Cached */
> > +     for (i = 0; i < tlbnr; i++) {
> > +             vppn = 0x80000000ULL + (i * SZ_2G);
> > +             create_tlb(index++, vppn, PS_1G, 1);
> > +     }
> > +}
> > +
> > +/*
> > + * set_virtual_map() - create a virtual mapping for the EFI memory map and call
> > + * efi_set_virtual_address_map enter virtual for runtime service
> > + *
> > + * This function populates the virt_addr fields of all memory region descriptors
> > + * in @memory_map whose EFI_MEMORY_RUNTIME attribute is set. Those descriptors
> > + * are also copied to @runtime_map, and their total count is returned in @count.
> > + */
> > +static unsigned int __init set_virtual_map(void)
> > +{
> > +     int count = 0;
> > +     unsigned int size;
> > +     unsigned long attr;
> > +     efi_status_t status;
> > +     efi_runtime_services_t *rt;
> > +     efi_set_virtual_address_map_t *svam;
> > +     efi_memory_desc_t *in, runtime_map[32];
> > +
> > +     size = sizeof(efi_memory_desc_t);
> > +
> > +     for_each_efi_memory_desc(in) {
> > +             attr = in->attribute;
> > +             if (!(attr & EFI_MEMORY_RUNTIME))
> > +                     continue;
> > +
> > +             if (attr & (EFI_MEMORY_WB | EFI_MEMORY_WT))
> > +                     in->virt_addr = TO_CACHE(in->phys_addr);
> > +             else
> > +                     in->virt_addr = TO_UNCACHE(in->phys_addr);
> > +
> > +             memcpy(&runtime_map[count++], in, size);
> > +     }
> > +
> > +     rt = early_memremap_ro((unsigned long)efi_systab->runtime, sizeof(*rt));
> > +
> > +     /* Install the new virtual address map */
> > +     svam = rt->set_virtual_address_map;
> > +
> > +     fix_efi_mapping();
> > +
> > +     status = svam(size * count, size, efi.memmap.desc_version,
> > +                     (efi_memory_desc_t *)TO_PHYS((unsigned long)runtime_map));
> > +
> > +     local_flush_tlb_all();
> > +     write_csr_pagesize(PS_DEFAULT_SIZE);
> > +
> > +     if (status != EFI_SUCCESS)
> > +             return -1;
> > +
> > +     return 0;
> > +}
> > +
> > +void __init efi_runtime_init(void)
> > +{
> > +     efi_status_t status;
> > +
> > +     if (!efi_enabled(EFI_BOOT))
> > +             return;
> > +
> > +     if (!efi_systab->runtime)
> > +             return;
> > +
> > +     status = set_virtual_map();
> > +     if (status < 0)
> > +             return;
> > +
> > +     if (efi_runtime_disabled()) {
> > +             pr_info("EFI runtime services will be disabled.\n");
> > +             return;
> > +     }
> > +
> > +     efi.runtime = (efi_runtime_services_t *)efi_systab->runtime;
> > +     efi.runtime_version = (unsigned int)efi.runtime->hdr.revision;
> > +
> > +     efi_native_runtime_setup();
> > +     set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
> > +}
> > +
> > +void __init efi_init(void)
> > +{
> > +     int size;
> > +     void *config_tables;
> > +
> > +     if (!efi_system_table)
> > +             return;
> > +
> > +     efi_systab = (efi_system_table_t *)early_memremap_ro(efi_system_table, sizeof(efi_systab));
> > +     if (!efi_systab) {
> > +             pr_err("Can't find EFI system table.\n");
> > +             return;
> > +     }
> > +
> > +     set_bit(EFI_64BIT, &efi.flags);
> > +     efi_nr_tables    = efi_systab->nr_tables;
> > +     efi_config_table = (unsigned long)efi_systab->tables;
> > +
> > +     size = sizeof(efi_config_table_t);
> > +     config_tables = early_memremap(efi_config_table, efi_nr_tables * size);
> > +     efi_config_parse_tables(config_tables, efi_systab->nr_tables, arch_tables);
> > +     early_memunmap(config_tables, efi_nr_tables * size);
> > +
> > +     init_screen_info();
> > +}
> > +
> > +static ssize_t boardinfo_show(struct kobject *kobj,
> > +                           struct kobj_attribute *attr, char *buf)
> > +{
> > +     return sprintf(buf,
> > +             "BIOS Information\n"
> > +             "Vendor\t\t\t: %s\n"
> > +             "Version\t\t\t: %s\n"
> > +             "ROM Size\t\t: %d KB\n"
> > +             "Release Date\t\t: %s\n\n"
> > +             "Board Information\n"
> > +             "Manufacturer\t\t: %s\n"
> > +             "Board Name\t\t: %s\n"
> > +             "Family\t\t\t: LOONGSON64\n\n",
> > +             b_info.bios_vendor, b_info.bios_version,
> > +             b_info.bios_size, b_info.bios_release_date,
> > +             b_info.board_vendor, b_info.board_name);
> > +}
> > +
> > +static struct kobj_attribute boardinfo_attr = __ATTR(boardinfo, 0444,
> > +                                                  boardinfo_show, NULL);
> > +
> > +static int __init boardinfo_init(void)
> > +{
> > +     if (!efi_kobj)
> > +             return -EINVAL;
> > +
> > +     return sysfs_create_file(efi_kobj, &boardinfo_attr.attr);
> > +}
> > +late_initcall(boardinfo_init);
> > diff --git a/arch/loongarch/kernel/env.c b/arch/loongarch/kernel/env.c
> > new file mode 100644
> > index 000000000000..bf2593f1e536
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/env.c
> > @@ -0,0 +1,70 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Author: Huacai Chen <chenhuacai@...ngson.cn>
> > + *
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#include <linux/acpi.h>
> > +#include <linux/efi.h>
> > +#include <linux/export.h>
> > +#include <linux/memblock.h>
> > +#include <linux/of_fdt.h>
> > +#include <asm/early_ioremap.h>
> > +#include <asm/bootinfo.h>
> > +#include <asm/loongson.h>
> > +
> > +u64 efi_system_table;
> > +struct loongson_system_configuration loongson_sysconf;
> > +EXPORT_SYMBOL(loongson_sysconf);
> > +
> > +u64 loongson_chipcfg[MAX_PACKAGES];
> > +u64 loongson_chiptemp[MAX_PACKAGES];
> > +u64 loongson_freqctrl[MAX_PACKAGES];
> > +unsigned long long smp_group[MAX_PACKAGES];
> > +
> > +static void __init register_addrs_set(u64 *registers, const u64 addr, int num)
> > +{
> > +     u64 i;
> > +
> > +     for (i = 0; i < num; i++) {
> > +             *registers = (i << 44) | addr;
> > +             registers++;
> > +     }
> > +}
> > +
> > +void __init init_environ(void)
> > +{
> > +     int efi_boot = fw_arg0;
> > +     struct efi_memory_map_data data;
> > +     void *fdt_ptr = early_memremap_ro(fw_arg1, SZ_64K);
> > +
> > +     if (efi_boot)
> > +             set_bit(EFI_BOOT, &efi.flags);
> > +     else
> > +             clear_bit(EFI_BOOT, &efi.flags);
> > +
> > +     early_init_dt_scan(fdt_ptr);
> > +     early_init_fdt_reserve_self();
> > +     efi_system_table = efi_get_fdt_params(&data);
> > +
> > +     efi_memmap_init_early(&data);
> > +     memblock_reserve(data.phys_map & PAGE_MASK,
> > +                      PAGE_ALIGN(data.size + (data.phys_map & ~PAGE_MASK)));
> > +
> > +     register_addrs_set(smp_group, TO_UNCACHE(0x1fe01000), 16);
> > +     register_addrs_set(loongson_chipcfg, TO_UNCACHE(0x1fe00180), 16);
> > +     register_addrs_set(loongson_chiptemp, TO_UNCACHE(0x1fe0019c), 16);
> > +     register_addrs_set(loongson_freqctrl, TO_UNCACHE(0x1fe001d0), 16);
> > +}
> > +
> > +static int __init init_cpu_fullname(void)
> > +{
> > +     int cpu;
> > +
> > +     if (loongson_sysconf.cpuname && !strncmp(loongson_sysconf.cpuname, "Loongson", 8)) {
> > +             for (cpu = 0; cpu < NR_CPUS; cpu++)
> > +                     __cpu_full_name[cpu] = loongson_sysconf.cpuname;
> > +     }
> > +     return 0;
> > +}
> > +arch_initcall(init_cpu_fullname);
> > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> > new file mode 100644
> > index 000000000000..f0b3e76bb762
> > --- /dev/null
> > +++ b/arch/loongarch/kernel/head.S
> > @@ -0,0 +1,97 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> > + */
> > +#include <linux/init.h>
> > +#include <linux/threads.h>
> > +
> > +#include <asm/addrspace.h>
> > +#include <asm/asm.h>
> > +#include <asm/asmmacro.h>
> > +#include <asm/regdef.h>
> > +#include <asm/loongarch.h>
> > +#include <asm/stackframe.h>
> > +#include <generated/compile.h>
> > +#include <generated/utsrelease.h>
> > +
> > +#ifdef CONFIG_EFI_STUB
> > +
> > +#include "efi-header.S"
> > +
> > +     __HEAD
> > +
> > +_head:
> > +     .word   MZ_MAGIC                /* "MZ", MS-DOS header */
> > +     .org    0x28
> > +     .ascii  "Loongson\0"            /* Magic number for BootLoader */
>
> If you must use a magic number, "Loongson" is not recommended, because
> this string lacks uniqueness in the Loongson/LoongArch world. Too many
> things are called "Loongson foo" right now, and the string is so
> ordinary people don't immediately think of it as "magic".
>
> I recommended using some other interesting text (and encoding) for the
> magic number, in a different communication venue, but I think that
> proposal got ignored by you without any explanation whatsoever. For now
> I'll just repeat myself:
>
> For an interesting magic number related to Loongson/LoongArch/Loong
> (like dragons but not exactly the same, let's not expand on that front)
> in general, it's perhaps better to use GB18030-encoded four-character
> dragon-related idioms. It's GB18030 because one Chinese character is 2
> bytes in this encoding, and being non-UTF-8 it's unlikely any user input
> would accidentally resemble it. So we get 8 bytes that appear as huge
> negative numbers if cast into C long, and random enough that collisions
> are highly unlikely.
>
> For example, I chose 4 famous dragon-related phrases from the I Ching,
> in both simplified and traditional characters:
>
> 潜龙勿用: 0xc7b1c1facef0d3c3
> 见龙在田: 0xbcfbc1fad4daccef
> 飞龙在天: 0xb7c9c1fad4daccec
> 亢龙有悔: 0xbfbac1fad3d0bbda
> 潛龍勿用: 0x9d93fd88cef0d3c3
> 見龍在田: 0xd28afd88d4daccef
> 飛龍在天: 0xef77fd88d4daccec
> 亢龍有悔: 0xbfbafd88d3d0bbda
>
> and I think each of them is better than "Loongson".
ARM64_IMAGE_MAGIC is "ARM64", RISCV_IMAGE_MAGIC is "RISCV", so I think
we use "Loongson" as a magic is just OK.

>
> > +     .org    0x3c
> > +     .long   pe_header - _head       /* Offset to the PE header */
> > +
> > +pe_header:
> > +     __EFI_PE_HEADER
> > +
> > +SYM_DATA(kernel_asize, .long _end - _text);
> > +SYM_DATA(kernel_fsize, .long _edata - _text);
> > +SYM_DATA(kernel_offset, .long kernel_offset - _text);
> > +
> > +kernel_version:
> > +     .ascii  UTS_RELEASE " (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ") " UTS_VERSION "\0"
> > +
> > +#endif
> > +
> > +     __REF
> > +
> > +SYM_ENTRY(_stext, SYM_L_GLOBAL, SYM_A_NONE)
> > +
> > +SYM_CODE_START(kernel_entry)                 # kernel entry point
> > +
> > +     /* Config direct window and set PG */
> > +     li.d            t0, CSR_DMW0_INIT       # UC, PLV0, 0x8000 xxxx xxxx xxxx
> > +     csrwr           t0, LOONGARCH_CSR_DMWIN0
> > +     li.d            t0, CSR_DMW1_INIT       # CA, PLV0, 0x9000 xxxx xxxx xxxx
> > +     csrwr           t0, LOONGARCH_CSR_DMWIN1
> > +     /* Enable PG */
> > +     li.w            t0, 0xb0                # PLV=0, IE=0, PG=1
> > +     csrwr           t0, LOONGARCH_CSR_CRMD
> > +     li.w            t0, 0x04                # PLV=0, PIE=1, PWE=0
> > +     csrwr           t0, LOONGARCH_CSR_PRMD
> > +     li.w            t0, 0x00                # FPE=0, SXE=0, ASXE=0, BTE=0
> > +     csrwr           t0, LOONGARCH_CSR_EUEN
> > +
> > +     /* We might not get launched at the address the kernel is linked to,
> > +        so we jump there.  */
> > +     la.abs          t0, 0f
> > +     jirl            zero, t0, 0
> > +0:
> > +     la              t0, __bss_start         # clear .bss
> > +     st.d            zero, t0, 0
> > +     la              t1, __bss_stop - LONGSIZE
> > +1:
> > +     addi.d          t0, t0, LONGSIZE
> > +     st.d            zero, t0, 0
> > +     bne             t0, t1, 1b
> > +
> > +     la              t0, fw_arg0
> > +     st.d            a0, t0, 0               # firmware arguments
> > +     la              t0, fw_arg1
> > +     st.d            a1, t0, 0
> > +     la              t0, fw_arg2
> > +     st.d            a2, t0, 0
> We don't use a2 any more with this revision of boot protocol, so this
> could get removed.
> > +
> > +     /* KScratch3 used for percpu base, initialized as 0 */
> > +     csrwr           zero, PERCPU_BASE_KS
>
> KScratch3 is MIPS-ism, it's SAVE3 in LoongArch.
OK, I will change all KScratch to KSave.

Huacai
>
> Also, reading the manual it's only guaranteed that at least 1 SAVE
> register is available, and we're not checking CSR.PRCFG1.SAVENum for
> number of implemented SAVE registers.
>
> Having said that, the only LoongArch implementation does have this
> register, and future models would require adaptation to work after all,
> so keeping as-is is somewhat okay.
>
> (No further comments below.)
>
> > +     /* GPR21 used for percpu base (runtime), initialized as 0 */
> > +     or              u0, zero, zero
> > +
> > +     la              tp, init_thread_union
> > +     /* Set the SP after an empty pt_regs.  */
> > +     PTR_LI          sp, (_THREAD_SIZE - 32 - PT_SIZE)
> > +     PTR_ADD         sp, sp, tp
> > +     set_saved_sp    sp, t0, t1
> > +     PTR_ADDI        sp, sp, -4 * SZREG      # init stack pointer
> > +
> > +     bl              start_kernel
> > +
> > +SYM_CODE_END(kernel_entry)
> > +
> > +SYM_ENTRY(kernel_entry_end, SYM_L_GLOBAL, SYM_A_NONE)
> (rest of patch snipped)

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