linux-kernel - Re: [PATCH v3 18/30] drivers/cpu: Add generic armv8 cpu driver

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Message-ID: <CALeDE9Mgpdg7CFJtosOT3fJBnQdrx-D7Rp91ownaGxKrwLfu3Q@mail.gmail.com>
Date: Wed, 11 Sep 2024 10:41:59 +0100
From: Peter Robinson <pbrobinson@...il.com>
To: Patrick Rudolph <patrick.rudolph@...ements.com>
Cc: u-boot@...ts.denx.de, linux-kernel@...r.kernel.org, 
	Tom Rini <trini@...sulko.com>, Simon Glass <sjg@...omium.org>
Subject: Re: [PATCH v3 18/30] drivers/cpu: Add generic armv8 cpu driver

Hi Patrick,

> Add a generic driver that binds to armv8 CPU nodes.

What is the purpose of this driver? Someone reading this should be
able to ascertain the point of this from the git log at some point in
the future, what does binding a generic driver to the cpu nodes
achieve?

> TEST: Booted on QEMU sbsa and verify the driver binds to CPU nodes.
>       Confirmed with FWTS that all ACPI processor devices are present.

This comment I think should be below the -- bit

> Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
> Cc: Tom Rini <trini@...sulko.com>
> Cc: Simon Glass <sjg@...omium.org>
> ---
>  drivers/cpu/Kconfig     |  6 +++
>  drivers/cpu/Makefile    |  2 +
>  drivers/cpu/armv8_cpu.c | 90 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 98 insertions(+)
>  create mode 100644 drivers/cpu/armv8_cpu.c
>
> diff --git a/drivers/cpu/Kconfig b/drivers/cpu/Kconfig
> index 5c06cd9f60..9c0df331d7 100644
> --- a/drivers/cpu/Kconfig
> +++ b/drivers/cpu/Kconfig
> @@ -26,6 +26,12 @@ config CPU_RISCV
>         help
>           Support CPU cores for RISC-V architecture.
>
> +config CPU_ARMV8
> +       bool "Enable generic ARMv8 CPU driver"
> +       depends on CPU && ARM64
> +       help
> +         Support CPU cores for armv8 architecture.
> +
>  config CPU_MICROBLAZE
>         bool "Enable Microblaze CPU driver"
>         depends on CPU && MICROBLAZE
> diff --git a/drivers/cpu/Makefile b/drivers/cpu/Makefile
> index bc75d9b974..773395693a 100644
> --- a/drivers/cpu/Makefile
> +++ b/drivers/cpu/Makefile
> @@ -6,10 +6,12 @@
>
>  obj-$(CONFIG_CPU) += cpu-uclass.o
>
> +
>  obj-$(CONFIG_ARCH_BMIPS) += bmips_cpu.o
>  obj-$(CONFIG_ARCH_IMX8) += imx8_cpu.o
>  obj-$(CONFIG_ARCH_AT91) += at91_cpu.o
>  obj-$(CONFIG_ARCH_MEDIATEK) += mtk_cpu.o
> +obj-$(CONFIG_CPU_ARMV8) += armv8_cpu.o
>  obj-$(CONFIG_CPU_IMX) += imx8_cpu.o
>  obj-$(CONFIG_CPU_MPC83XX) += mpc83xx_cpu.o
>  obj-$(CONFIG_CPU_RISCV) += riscv_cpu.o
> diff --git a/drivers/cpu/armv8_cpu.c b/drivers/cpu/armv8_cpu.c
> new file mode 100644
> index 0000000000..08b8d45f6f
> --- /dev/null
> +++ b/drivers/cpu/armv8_cpu.c
> @@ -0,0 +1,90 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2019 Broadcom.
> + */
> +#include <acpi/acpigen.h>
> +#include <asm/armv8/cpu.h>
> +#include <cpu.h>
> +#include <dm.h>
> +#include <dm/acpi.h>
> +#include <asm/io.h>
> +#include <linux/bitops.h>
> +#include <linux/printk.h>
> +#include <linux/sizes.h>
> +
> +static int armv8_cpu_get_desc(const struct udevice *dev, char *buf, int size)
> +{
> +       int cpuid;
> +
> +       cpuid = (read_midr() & MIDR_PARTNUM_MASK) >> MIDR_PARTNUM_SHIFT;
> +
> +       snprintf(buf, size, "CPU MIDR %04x", cpuid);
> +
> +       return 0;
> +}
> +
> +static int armv8_cpu_get_info(const struct udevice *dev,
> +                             struct cpu_info *info)
> +{
> +       info->cpu_freq = 0;
> +       info->features = BIT(CPU_FEAT_L1_CACHE) | BIT(CPU_FEAT_MMU);
> +
> +       return 0;
> +}
> +
> +static int armv8_cpu_get_count(const struct udevice *dev)
> +{
> +       ofnode node;
> +       int num = 0;
> +
> +       ofnode_for_each_subnode(node, dev_ofnode(dev->parent)) {
> +               const char *device_type;
> +
> +               if (!ofnode_is_enabled(node))
> +                       continue;
> +
> +               device_type = ofnode_read_string(node, "device_type");
> +               if (!device_type)
> +                       continue;
> +
> +               if (!strcmp(device_type, "cpu"))
> +                       num++;
> +       }
> +
> +       return num;
> +}
> +
> +#ifdef CONFIG_ACPIGEN
> +static int acpi_cpu_fill_ssdt(const struct udevice *dev, struct acpi_ctx *ctx)
> +{
> +       uint core_id = dev_seq(dev);
> +
> +       acpigen_write_processor_device(ctx, core_id);
> +
> +       return 0;
> +}
> +
> +struct acpi_ops armv8_cpu_acpi_ops = {
> +       .fill_ssdt      = acpi_cpu_fill_ssdt,
> +};
> +#endif
> +
> +static const struct cpu_ops cpu_ops = {
> +       .get_count = armv8_cpu_get_count,
> +       .get_desc  = armv8_cpu_get_desc,
> +       .get_info  = armv8_cpu_get_info,
> +};
> +
> +static const struct udevice_id cpu_ids[] = {
> +       { .compatible = "arm,armv8" },
> +       {}
> +};
> +
> +U_BOOT_DRIVER(arm_cpu) = {
> +       .name           = "arm-cpu",
> +       .id             = UCLASS_CPU,
> +       .of_match       = cpu_ids,
> +       .ops            = &cpu_ops,
> +       .flags          = DM_FLAG_PRE_RELOC,
> +       ACPI_OPS_PTR(&armv8_cpu_acpi_ops)
> +};
> --
> 2.46.0
>