Re: [PATCH 2/3] arm64: cpuinfo: add human readable CPU names to /proc/cpuinfo

[Robin Murphy]

On 26/09/17 23:23, Al Stone wrote:
> In the interest of making things easier for humans to use, add a
> "CPU name" line to /proc/cpuinfo for each CPU that uses plain old
> words instead of hex values.  For example, instead of printing only
> CPU implementer 0x43 and CPU part 0x0A1, print also "CPU name :
> Cavium ThunderX".
> 
> Note that this is not meant to be an exhaustive list of all possible
> implementers or CPUs (I'm not even sure that is knowable); this patch
> is intentionally limited to only those willing to provide info in
> arch/arm64/include/asm/cputype.h

How valuable is an incomplete interface really? If users who want to
decode MIDRs are going to have to rely on (pretty trivial ) userspace
tools anyway when their stable distro kernel doesn't know their spangly
new hardware, why does the kernel need to bother at all.

The fact is that we already do the exact same thing as x86 - we print
exactly what the ID registers say. The fact that on x86 some of those
values happen to form a readable ASCII string is a different matter.

> Signed-off-by: Al Stone <ahs3@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> ---
>  arch/arm64/kernel/cpuinfo.c | 84 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 84 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index e505007138eb..0b4261884862 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -75,6 +75,61 @@ static const char *const hwcap_str[] = {
>  	NULL
>  };
>  
> +struct hw_part {
> +	u16	id;
> +	char	*name;
> +};
> +
> +static const struct hw_part arm_hw_part[] = {
> +	{ ARM_CPU_PART_AEM_V8,		"AEMv8 Model" },
> +	{ ARM_CPU_PART_FOUNDATION,	"Foundation Model" },
> +	{ ARM_CPU_PART_CORTEX_A57,	"Cortex A57" },
> +	{ ARM_CPU_PART_CORTEX_A53,	"Cortex A53" },
> +	{ ARM_CPU_PART_CORTEX_A73,	"Cortex A73" },
> +	{ (-1), "unknown" }		/* Potenza == 0, unfortunately */

So for a fair chunk of *current* server-class hardware, we'll be
printing "unknown" already. Great.

Robin.

> +};
> +
> +static const struct hw_part apm_hw_part[] = {
> +	{ APM_CPU_PART_POTENZA,		"Potenza" },
> +	{ (-1), "unknown" }		/* Potenza == 0, unfortunately */
> +};
> +
> +static const struct hw_part brcm_hw_part[] = {
> +	{ BRCM_CPU_PART_VULCAN,		"Vulcan" },
> +	{ (-1), "unknown" }		/* Potenza == 0, unfortunately */
> +};
> +
> +static const struct hw_part cavium_hw_part[] = {
> +	{ CAVIUM_CPU_PART_THUNDERX,	 "ThunderX" },
> +	{ CAVIUM_CPU_PART_THUNDERX_81XX, "ThunderX 81XX" },
> +	{ CAVIUM_CPU_PART_THUNDERX_83XX, "ThunderX 83XX" },
> +	{ (-1), "unknown" }		/* Potenza == 0, unfortunately */
> +};
> +
> +static const struct hw_part qcom_hw_part[] = {
> +	{ QCOM_CPU_PART_FALKOR_V1,	"Falkor v1" },
> +	{ (-1), "unknown" }		/* Potenza == 0, unfortunately */
> +};
> +
> +static const struct hw_part unknown_hw_part[] = {
> +	{ (-1), "unknown" }		/* Potenza == 0, unfortunately */
> +};
> +
> +struct hw_impl {
> +	u8			id;
> +	const struct hw_part	*parts;
> +	char			*name;
> +};
> +
> +static const struct hw_impl hw_implementer[] = {
> +	{ ARM_CPU_IMP_ARM,	arm_hw_part,	"ARM Ltd." },
> +	{ ARM_CPU_IMP_APM,	apm_hw_part,	"Applied Micro" },
> +	{ ARM_CPU_IMP_CAVIUM,	cavium_hw_part,	"Cavium" },
> +	{ ARM_CPU_IMP_BRCM,	brcm_hw_part,	"Broadcom" },
> +	{ ARM_CPU_IMP_QCOM,	qcom_hw_part,	"Qualcomm" },
> +	{ 0, unknown_hw_part, "unknown" }
> +};
> +
>  #ifdef CONFIG_COMPAT
>  static const char *const compat_hwcap_str[] = {
>  	"swp",
> @@ -116,6 +171,9 @@ static int c_show(struct seq_file *m, void *v)
>  {
>  	int i, j;
>  	bool compat = personality(current->personality) == PER_LINUX32;
> +	u8 impl;
> +	u16 part;
> +	const struct hw_part *parts;
>  
>  	for_each_online_cpu(i) {
>  		struct cpuinfo_arm64 *cpuinfo = &per_cpu(cpu_data, i);
> @@ -132,6 +190,32 @@ static int c_show(struct seq_file *m, void *v)
>  			seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",
>  				   MIDR_REVISION(midr), COMPAT_ELF_PLATFORM);
>  
> +		impl = (u8) MIDR_IMPLEMENTOR(midr);
> +		for (j = 0; hw_implementer[j].id != 0; j++) {
> +			if (hw_implementer[j].id == impl) {
> +				seq_printf(m, "CPU name\t: %s ",
> +					   hw_implementer[j].name);
> +				parts = hw_implementer[j].parts;
> +				break;
> +			}
> +		}
> +		if (hw_implementer[j].id == 0) {
> +			seq_printf(m, "CPU name\t: %s ",
> +				   hw_implementer[j].name);
> +			parts = hw_implementer[j].parts;
> +		}
> +
> +		part = (u16) MIDR_PARTNUM(midr);
> +		for (j = 0; parts[j].id != (-1); j++) {
> +			if (parts[j].id == part) {
> +				seq_printf(m, "%s\n", parts[j].name);
> +				break;
> +			}
> +		}
> +		if (parts[j].id == (-1))
> +			seq_printf(m, "%s", parts[j].name);
> +		seq_puts(m, "\n");
> +
>  		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n",
>  			   loops_per_jiffy / (500000UL/HZ),
>  			   loops_per_jiffy / (5000UL/HZ) % 100);
>