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

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

On 2/4/2024 20:29, Yuan, Perry wrote:
> [AMD Official Use Only - General]
> 
>> -----Original Message-----
>> From: Oleksandr Natalenko <oleksandr@natalenko.name>
>> Sent: Sunday, February 4, 2024 10:45 PM
>> To: rafael.j.wysocki@intel.com; Limonciello, Mario
>> <Mario.Limonciello@amd.com>; viresh.kumar@linaro.org; Huang, Ray
>> <Ray.Huang@amd.com>; Shenoy, Gautham Ranjal
>> <gautham.shenoy@amd.com>; Petkov, Borislav
>> <Borislav.Petkov@amd.com>; Yuan, Perry <Perry.Yuan@amd.com>
>> Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Huang, Shimmer
>> <Shimmer.Huang@amd.com>; Du, Xiaojian <Xiaojian.Du@amd.com>; Meng,
>> Li (Jassmine) <Li.Meng@amd.com>; linux-pm@vger.kernel.org; linux-
>> kernel@vger.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@amd.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.
> 
> Good catch, I made a mistake here, I found this after I sent it out,  have it fixed in V4.
> Thanks for the review.

I'm still wondering if this is the right level of narrowness.  Does the 
quirk only apply to a single BIOS vendor?  Or any other sysfs attributes 
that can be generic to all affected systems?

Also would it perhaps make sense to rename dmi_matched to 
dmi_matched_7k62_bios_bug and then in dmi_matched_7k62_bios_bug check 
the model/family match.  In that function you can only set
quirks = dmi->driver_data

If the right CPU applies then too.

> 
> Perry.
> 
>>
>>> +           },
>>> +           .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)