linux-kernel - Re: [PATCH v3 6/6] cpufreq:amd-pstate: add quirk for the pstate CPPC capabilities missing

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Date: Sun, 04 Feb 2024 15:45:19 +0100
From: Oleksandr Natalenko <oleksandr@...alenko.name>
To: rafael.j.wysocki@...el.com, Mario.Limonciello@....com,
 viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
 Borislav.Petkov@....com, Perry Yuan <perry.yuan@....com>
Cc: Alexander.Deucher@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
 Li.Meng@....com, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject:
 Re: [PATCH v3 6/6] cpufreq:amd-pstate: add quirk for the pstate CPPC
 capabilities missing

Hello.

On neděle 4. února 2024 4:26:14 CET 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
> 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@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 49 ++++++++++++++++++++++++++++++++++--
>  include/linux/amd-pstate.h   |  6 +++++
>  2 files changed, 53 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 77effc3caf6c..25a6d8a808c4 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 +112,33 @@ 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(const struct dmi_system_id *dmi)
> +{
> +	quirks = dmi->driver_data;
> +	pr_info("hardware type %s found\n", dmi->ident);
> +
> +	return 1;
> +}
> +
> +static const struct dmi_system_id amd_pstate_quirks_table[] __initconst = {
> +	{
> +		.callback = dmi_matched,
> +		.ident = "AMD EPYC 7K62",
> +		.matches = {
> +			DMI_MATCH(DMI_BIOS_VERSION, "5.14"),
> +			DMI_MATCH(DMI_BIOS_RELEASE, "12/12/2019");

I think this is incorrect, and there should be a comma "," instead of semicolon ";" at the end of the string. Otherwise the build will fail.

> +		},
> +		.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 +628,19 @@ 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 +669,18 @@ 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 +1712,11 @@ 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 */
> 


-- 
Oleksandr Natalenko (post-factum)
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