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Date:   Tue, 04 Aug 2020 18:47:54 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Anup Patel <Anup.Patel@....com>
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        robh+dt@...nel.org, daniel.lezcano@...aro.org, tglx@...utronix.de,
        Damien Le Moal <Damien.LeMoal@....com>,
        Atish Patra <Atish.Patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        anup@...infault.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Anup Patel <Anup.Patel@....com>, kernel@...il.dk
Subject:     Re: [PATCH v6 3/4] RISC-V: Remove CLINT related code from timer and arch

On Fri, 24 Jul 2020 00:18:21 PDT (-0700), Anup Patel wrote:
> Right now the RISC-V timer driver is convoluted to support:
> 1. Linux RISC-V S-mode (with MMU) where it will use TIME CSR for
>    clocksource and SBI timer calls for clockevent device.
> 2. Linux RISC-V M-mode (without MMU) where it will use CLINT MMIO
>    counter register for clocksource and CLINT MMIO compare register
>    for clockevent device.
>
> We now have a separate CLINT timer driver which also provide CLINT
> based IPI operations so let's remove CLINT MMIO related code from
> arch/riscv directory and RISC-V timer driver.
>
> Signed-off-by: Anup Patel <anup.patel@....com>
> Tested-by: Emil Renner Berhing <kernel@...il.dk>
> Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  arch/riscv/Kconfig                      |  2 +-
>  arch/riscv/Kconfig.socs                 |  2 +
>  arch/riscv/configs/nommu_virt_defconfig |  7 +--
>  arch/riscv/include/asm/clint.h          | 14 ------
>  arch/riscv/include/asm/timex.h          | 28 +++--------
>  arch/riscv/kernel/Makefile              |  2 +-
>  arch/riscv/kernel/clint.c               | 63 -------------------------
>  arch/riscv/kernel/setup.c               |  2 -
>  arch/riscv/kernel/smp.c                 |  1 -
>  arch/riscv/kernel/smpboot.c             |  1 -
>  drivers/clocksource/Kconfig             |  3 +-
>  drivers/clocksource/timer-riscv.c       | 17 +------
>  12 files changed, 16 insertions(+), 126 deletions(-)
>  delete mode 100644 arch/riscv/include/asm/clint.h
>  delete mode 100644 arch/riscv/kernel/clint.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index fedb4a72b29a..57a72ae23d10 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -74,7 +74,7 @@ config RISCV
>  	select PCI_DOMAINS_GENERIC if PCI
>  	select PCI_MSI if PCI
>  	select RISCV_INTC
> -	select RISCV_TIMER
> +	select RISCV_TIMER if RISCV_SBI
>  	select SPARSEMEM_STATIC if 32BIT
>  	select SPARSE_IRQ
>  	select SYSCTL_EXCEPTION_TRACE
> diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
> index 6c88148f1b9b..8a55f6156661 100644
> --- a/arch/riscv/Kconfig.socs
> +++ b/arch/riscv/Kconfig.socs
> @@ -12,6 +12,7 @@ config SOC_SIFIVE
>
>  config SOC_VIRT
>  	bool "QEMU Virt Machine"
> +	select CLINT_TIMER if RISCV_M_MODE
>  	select POWER_RESET
>  	select POWER_RESET_SYSCON
>  	select POWER_RESET_SYSCON_POWEROFF
> @@ -24,6 +25,7 @@ config SOC_VIRT
>  config SOC_KENDRYTE
>  	bool "Kendryte K210 SoC"
>  	depends on !MMU
> +	select CLINT_TIMER if RISCV_M_MODE
>  	select SERIAL_SIFIVE if TTY
>  	select SERIAL_SIFIVE_CONSOLE if TTY
>  	select SIFIVE_PLIC
> diff --git a/arch/riscv/configs/nommu_virt_defconfig b/arch/riscv/configs/nommu_virt_defconfig
> index cf74e179bf90..cf9388184aa3 100644
> --- a/arch/riscv/configs/nommu_virt_defconfig
> +++ b/arch/riscv/configs/nommu_virt_defconfig
> @@ -26,6 +26,7 @@ CONFIG_EXPERT=y
>  CONFIG_SLOB=y
>  # CONFIG_SLAB_MERGE_DEFAULT is not set
>  # CONFIG_MMU is not set
> +CONFIG_SOC_VIRT=y
>  CONFIG_MAXPHYSMEM_2GB=y
>  CONFIG_SMP=y
>  CONFIG_CMDLINE="root=/dev/vda rw earlycon=uart8250,mmio,0x10000000,115200n8 console=ttyS0"
> @@ -48,7 +49,6 @@ CONFIG_VIRTIO_BLK=y
>  # CONFIG_SERIO is not set
>  # CONFIG_LEGACY_PTYS is not set
>  # CONFIG_LDISC_AUTOLOAD is not set
> -# CONFIG_DEVMEM is not set
>  CONFIG_SERIAL_8250=y
>  # CONFIG_SERIAL_8250_DEPRECATED_OPTIONS is not set
>  CONFIG_SERIAL_8250_CONSOLE=y
> @@ -56,16 +56,13 @@ CONFIG_SERIAL_8250_NR_UARTS=1
>  CONFIG_SERIAL_8250_RUNTIME_UARTS=1
>  CONFIG_SERIAL_OF_PLATFORM=y
>  # CONFIG_HW_RANDOM is not set
> +# CONFIG_DEVMEM is not set
>  # CONFIG_HWMON is not set
> -# CONFIG_LCD_CLASS_DEVICE is not set
> -# CONFIG_BACKLIGHT_CLASS_DEVICE is not set
>  # CONFIG_VGA_CONSOLE is not set
>  # CONFIG_HID is not set
>  # CONFIG_USB_SUPPORT is not set
>  CONFIG_VIRTIO_MMIO=y
>  CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=y
> -CONFIG_SIFIVE_PLIC=y
> -# CONFIG_VALIDATE_FS_PARSER is not set
>  CONFIG_EXT2_FS=y
>  # CONFIG_DNOTIFY is not set
>  # CONFIG_INOTIFY_USER is not set
> diff --git a/arch/riscv/include/asm/clint.h b/arch/riscv/include/asm/clint.h
> deleted file mode 100644
> index adaba98a7d6c..000000000000
> --- a/arch/riscv/include/asm/clint.h
> +++ /dev/null
> @@ -1,14 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -#ifndef _ASM_RISCV_CLINT_H
> -#define _ASM_RISCV_CLINT_H 1
> -
> -#include <linux/io.h>
> -#include <linux/smp.h>
> -
> -#ifdef CONFIG_RISCV_M_MODE
> -void clint_init_boot_cpu(void);
> -#else /* CONFIG_RISCV_M_MODE */
> -#define clint_init_boot_cpu()	do { } while (0)
> -#endif /* CONFIG_RISCV_M_MODE */
> -
> -#endif /* _ASM_RISCV_CLINT_H */
> diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
> index bad2a7c2cda5..a3fb85d505d4 100644
> --- a/arch/riscv/include/asm/timex.h
> +++ b/arch/riscv/include/asm/timex.h
> @@ -7,41 +7,27 @@
>  #define _ASM_RISCV_TIMEX_H
>
>  #include <asm/csr.h>
> -#include <asm/mmio.h>
>
>  typedef unsigned long cycles_t;
>
> -extern u64 __iomem *riscv_time_val;
> -extern u64 __iomem *riscv_time_cmp;
> -
> -#ifdef CONFIG_64BIT
> -#define mmio_get_cycles()	readq_relaxed(riscv_time_val)
> -#else
> -#define mmio_get_cycles()	readl_relaxed(riscv_time_val)
> -#define mmio_get_cycles_hi()	readl_relaxed(((u32 *)riscv_time_val) + 1)
> -#endif
> -
>  static inline cycles_t get_cycles(void)
>  {
> -	if (IS_ENABLED(CONFIG_RISCV_SBI))
> -		return csr_read(CSR_TIME);
> -	return mmio_get_cycles();
> +	return csr_read(CSR_TIME);
>  }
>  #define get_cycles get_cycles
>
> +static inline u32 get_cycles_hi(void)
> +{
> +	return csr_read(CSR_TIMEH);
> +}
> +#define get_cycles_hi get_cycles_hi
> +
>  #ifdef CONFIG_64BIT
>  static inline u64 get_cycles64(void)
>  {
>  	return get_cycles();
>  }
>  #else /* CONFIG_64BIT */
> -static inline u32 get_cycles_hi(void)
> -{
> -	if (IS_ENABLED(CONFIG_RISCV_SBI))
> -		return csr_read(CSR_TIMEH);
> -	return mmio_get_cycles_hi();
> -}
> -
>  static inline u64 get_cycles64(void)
>  {
>  	u32 hi, lo;
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index b355cf485671..7edf15643146 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -31,7 +31,7 @@ obj-y	+= cacheinfo.o
>  obj-y	+= patch.o
>  obj-$(CONFIG_MMU) += vdso.o vdso/
>
> -obj-$(CONFIG_RISCV_M_MODE)	+= clint.o traps_misaligned.o
> +obj-$(CONFIG_RISCV_M_MODE)	+= traps_misaligned.o
>  obj-$(CONFIG_FPU)		+= fpu.o
>  obj-$(CONFIG_SMP)		+= smpboot.o
>  obj-$(CONFIG_SMP)		+= smp.o
> diff --git a/arch/riscv/kernel/clint.c b/arch/riscv/kernel/clint.c
> deleted file mode 100644
> index a9845ee023e2..000000000000
> --- a/arch/riscv/kernel/clint.c
> +++ /dev/null
> @@ -1,63 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/*
> - * Copyright (c) 2019 Christoph Hellwig.
> - */
> -
> -#include <linux/io.h>
> -#include <linux/of_address.h>
> -#include <linux/smp.h>
> -#include <linux/types.h>
> -#include <asm/clint.h>
> -#include <asm/csr.h>
> -#include <asm/timex.h>
> -
> -/*
> - * This is the layout used by the SiFive clint, which is also shared by the qemu
> - * virt platform, and the Kendryte KD210 at least.
> - */
> -#define CLINT_IPI_OFF		0
> -#define CLINT_TIME_CMP_OFF	0x4000
> -#define CLINT_TIME_VAL_OFF	0xbff8
> -
> -u32 __iomem *clint_ipi_base;
> -
> -static void clint_send_ipi(const struct cpumask *target)
> -{
> -	unsigned int cpu;
> -
> -	for_each_cpu(cpu, target)
> -		writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
> -}
> -
> -static void clint_clear_ipi(void)
> -{
> -	writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
> -}
> -
> -static struct riscv_ipi_ops clint_ipi_ops = {
> -	.ipi_inject = clint_send_ipi,
> -	.ipi_clear = clint_clear_ipi,
> -};
> -
> -void clint_init_boot_cpu(void)
> -{
> -	struct device_node *np;
> -	void __iomem *base;
> -
> -	np = of_find_compatible_node(NULL, NULL, "riscv,clint0");
> -	if (!np) {
> -		panic("clint not found");
> -		return;
> -	}
> -
> -	base = of_iomap(np, 0);
> -	if (!base)
> -		panic("could not map CLINT");
> -
> -	clint_ipi_base = base + CLINT_IPI_OFF;
> -	riscv_time_cmp = base + CLINT_TIME_CMP_OFF;
> -	riscv_time_val = base + CLINT_TIME_VAL_OFF;
> -
> -	clint_clear_ipi();
> -	riscv_set_ipi_ops(&clint_ipi_ops);
> -}
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index f04373be54a6..2c6dd329312b 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -18,7 +18,6 @@
>  #include <linux/swiotlb.h>
>  #include <linux/smp.h>
>
> -#include <asm/clint.h>
>  #include <asm/cpu_ops.h>
>  #include <asm/setup.h>
>  #include <asm/sections.h>
> @@ -79,7 +78,6 @@ void __init setup_arch(char **cmdline_p)
>  #else
>  	unflatten_device_tree();
>  #endif
> -	clint_init_boot_cpu();
>
>  #ifdef CONFIG_SWIOTLB
>  	swiotlb_init(1);
> diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
> index 8b85683ce203..07626be78c23 100644
> --- a/arch/riscv/kernel/smp.c
> +++ b/arch/riscv/kernel/smp.c
> @@ -17,7 +17,6 @@
>  #include <linux/seq_file.h>
>  #include <linux/delay.h>
>
> -#include <asm/clint.h>
>  #include <asm/sbi.h>
>  #include <asm/tlbflush.h>
>  #include <asm/cacheflush.h>
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 5fe849791bf0..a6cfa9842d4b 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -24,7 +24,6 @@
>  #include <linux/of.h>
>  #include <linux/sched/task_stack.h>
>  #include <linux/sched/mm.h>
> -#include <asm/clint.h>
>  #include <asm/cpu_ops.h>
>  #include <asm/irq.h>
>  #include <asm/mmu_context.h>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 41f1c147c178..b24449da3022 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -648,9 +648,8 @@ config ATCPIT100_TIMER
>  	  This option enables support for the Andestech ATCPIT100 timers.
>
>  config RISCV_TIMER
> -	bool "Timer for the RISC-V platform"
> +	bool "Timer for the RISC-V platform" if COMPILE_TEST
>  	depends on GENERIC_SCHED_CLOCK && RISCV
> -	default y
>  	select TIMER_PROBE
>  	select TIMER_OF
>  	help
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 9de1dabfb126..c51c5ed15aa7 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -19,26 +19,13 @@
>  #include <linux/of_irq.h>
>  #include <asm/smp.h>
>  #include <asm/sbi.h>
> -
> -u64 __iomem *riscv_time_cmp;
> -u64 __iomem *riscv_time_val;
> -
> -static inline void mmio_set_timer(u64 val)
> -{
> -	void __iomem *r;
> -
> -	r = riscv_time_cmp + cpuid_to_hartid_map(smp_processor_id());
> -	writeq_relaxed(val, r);
> -}
> +#include <asm/timex.h>
>
>  static int riscv_clock_next_event(unsigned long delta,
>  		struct clock_event_device *ce)
>  {
>  	csr_set(CSR_IE, IE_TIE);
> -	if (IS_ENABLED(CONFIG_RISCV_SBI))
> -		sbi_set_timer(get_cycles64() + delta);
> -	else
> -		mmio_set_timer(get_cycles64() + delta);
> +	sbi_set_timer(get_cycles64() + delta);
>  	return 0;
>  }

Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>

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