Re: [PATCH v4 6/6] cpufreq:amd-pstate: add quirk for the pstate CPPC capabilities missing

[Mario Limonciello <mario.limonciello@amd.com>]

On 2/5/2024 22:33, Perry Yuan wrote:
> Add quirks table to get CPPC capabilities issue fixed by providing
> correct perf or frequency values while driver loading.
> 
> If CPPC capabilities are not defined in the ACPI tables or wrongly
> defined by platform firmware, it needs to use quick to get those
s,quick,a quirk,
> issues fixed with correct workaround values to make pstate driver
> can be loaded even though there are CPPC capabilities errors.
> 
> The workaround will match the broken BIOS which lack of CPPC capabilities
> nominal_freq and lowest_freq definition in the ACPI table.
> 
> $ cat /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq
> 0
> $ cat /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq
> 0
> 
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>
> ---
>   drivers/cpufreq/amd-pstate.c | 59 ++++++++++++++++++++++++++++++++++--
>   include/linux/amd-pstate.h   |  6 ++++
>   2 files changed, 63 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 77effc3caf6c..874d8b663790 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -67,6 +67,7 @@ static struct cpufreq_driver amd_pstate_epp_driver;
>   static int cppc_state = AMD_PSTATE_UNDEFINED;
>   static bool cppc_enabled;
>   static bool amd_pstate_prefcore = true;
> +static struct quirk_entry *quirks;
>   
>   /*
>    * AMD Energy Preference Performance (EPP)
> @@ -111,6 +112,43 @@ static unsigned int epp_values[] = {
>   
>   typedef int (*cppc_mode_transition_fn)(int);
>   
> +static struct quirk_entry quirk_amd_7k62 = {
> +	.nominal_freq = 2600,
> +	.lowest_freq = 550,
> +};
> +
> +static int __init dmi_matched_7k62_bios_bug(const struct dmi_system_id *dmi)
> +{
> +	/**
> +	 * match the broken bios for family 17h, model 31h processor
> +	 * broken BIOS lack of nominal_freq and lowest_freq capabilities
> +	 * definition in ACPI tables
> +	 */
> +	if (boot_cpu_data.x86 == 0x17 && boot_cpu_data.x86_model == 0x31 &&
> +			boot_cpu_has(X86_FEATURE_ZEN2)) {

I think you should use one or the other (17/31) or (X86_FEATURE_ZEN2).

> +		quirks = dmi->driver_data;
> +		pr_info("hardware type %s found\n", dmi->ident);

I think a better message explains what is happening.  For example:
"Overriding nominal and lowest frequencies for %s\n"

> +		return 1;
> +	}
> +
> +

Only need one newline needed here.

> +	return 0;
> +}
> +
> +static const struct dmi_system_id amd_pstate_quirks_table[] __initconst = {
> +	{
> +		.callback = dmi_matched_7k62_bios_bug,
> +		.ident = "AMD EPYC 7K62",
> +		.matches = {
> +			DMI_MATCH(DMI_BIOS_VERSION, "5.14"),
> +			DMI_MATCH(DMI_BIOS_RELEASE, "12/12/2019"),
> +		},
> +		.driver_data = &quirk_amd_7k62,
> +	},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(dmi, amd_pstate_quirks_table);
> +
>   static inline int get_mode_idx_from_str(const char *str, size_t size)
>   {
>   	int i;
> @@ -600,13 +638,19 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
>   static int amd_get_min_freq(struct amd_cpudata *cpudata)
>   {
>   	struct cppc_perf_caps cppc_perf;
> +	u32 lowest_freq;
>   
>   	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
>   	if (ret)
>   		return ret;
>   
> +	if (quirks && quirks->lowest_freq)
> +		lowest_freq = quirks->lowest_freq;
> +	else
> +		lowest_freq = cppc_perf.lowest_freq;
> +
>   	/* Switch to khz */
> -	return cppc_perf.lowest_freq * 1000;
> +	return lowest_freq * 1000;
>   }
>   
>   static int amd_get_max_freq(struct amd_cpudata *cpudata)
> @@ -635,12 +679,18 @@ static int amd_get_max_freq(struct amd_cpudata *cpudata)
>   static int amd_get_nominal_freq(struct amd_cpudata *cpudata)
>   {
>   	struct cppc_perf_caps cppc_perf;
> +	u32 nominal_freq;
>   
>   	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
>   	if (ret)
>   		return ret;
>   
> -	return cppc_perf.nominal_freq;
> +	if (quirks && quirks->nominal_freq)
> +		nominal_freq = quirks->nominal_freq;
> +	else
> +		nominal_freq = cppc_perf.nominal_freq;
> +
> +	return nominal_freq;
>   }
>   
>   static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata)
> @@ -1672,6 +1722,11 @@ static int __init amd_pstate_init(void)
>   	if (cpufreq_get_current_driver())
>   		return -EEXIST;
>   
> +	quirks = NULL;
> +
> +	/* check if this machine need CPPC quirks */
> +	dmi_check_system(amd_pstate_quirks_table);
> +
>   	switch (cppc_state) {
>   	case AMD_PSTATE_UNDEFINED:
>   		/* Disable on the following configs by default:
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index d21838835abd..7b2cbb892fd9 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -124,4 +124,10 @@ static const char * const amd_pstate_mode_string[] = {
>   	[AMD_PSTATE_GUIDED]      = "guided",
>   	NULL,
>   };
> +
> +struct quirk_entry {
> +	u32 nominal_freq;
> +	u32 lowest_freq;
> +};
> +
>   #endif /* _LINUX_AMD_PSTATE_H */