Re: [PATCH v10 8/8] cpufreq: amd-pstate: Add quirk for the pstate CPPC capabilities missing

[Huang Rui]

On Mon, Mar 25, 2024 at 11:03:28AM +0800, Yuan, Perry 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
> 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
> 
> Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
> Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@xxxxxxx>
> Signed-off-by: Perry Yuan <perry.yuan@xxxxxxx>
> ---
>  drivers/cpufreq/amd-pstate.c | 53 ++++++++++++++++++++++++++++++++++--
>  include/linux/amd-pstate.h   |  6 ++++
>  2 files changed, 57 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index ec049b62b366..59a2db225d98 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;

If we set quirks as global pointer, while the amd-pstate is uninstalling,
should we free the quirks as well?

Thanks,
Ray

>  
>  /*
>   * AMD Energy Preference Performance (EPP)
> @@ -111,6 +112,41 @@ 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 processor support CPPC V2
> +	 * broken BIOS lack of nominal_freq and lowest_freq capabilities
> +	 * definition in ACPI tables
> +	 */
> +	if (boot_cpu_has(X86_FEATURE_ZEN2)) {
> +		quirks = dmi->driver_data;
> +		pr_info("Overriding nominal and lowest frequencies for %s\n", dmi->ident);
> +		return 1;
> +	}
> +
> +	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;
> @@ -812,8 +848,16 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
>  	if (ret)
>  		return ret;
>  
> -	min_freq = cppc_perf.lowest_freq * 1000;
> -	nominal_freq = cppc_perf.nominal_freq * 1000;
> +	if (quirks && quirks->lowest_freq)
> +		min_freq = quirks->lowest_freq * 1000;
> +	else
> +		min_freq = cppc_perf.lowest_freq * 1000;
> +
> +	if (quirks && quirks->nominal_freq)
> +		nominal_freq = quirks->nominal_freq * 1000;
> +	else
> +		nominal_freq = cppc_perf.nominal_freq * 1000;
> +
>  	nominal_perf = READ_ONCE(cpudata->nominal_perf);
>  
>  	highest_perf = READ_ONCE(cpudata->highest_perf);
> @@ -1662,6 +1706,11 @@ 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 ab7e82533718..6b832153a126 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -128,4 +128,10 @@ 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 */
> -- 
> 2.34.1
>