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

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Mario,

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Tuesday, February 6, 2024 11:46 PM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>; rafael.j.wysocki@xxxxxxxxx;
> viresh.kumar@xxxxxxxxxx; Huang, Ray <Ray.Huang@xxxxxxx>; Shenoy,
> Gautham Ranjal <gautham.shenoy@xxxxxxx>; Petkov, Borislav
> <Borislav.Petkov@xxxxxxx>
> Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng,
> Li (Jassmine) <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v4 6/6] cpufreq:amd-pstate: add quirk for the pstate
> CPPC capabilities missing
>
> 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@xxxxxxx>
> > ---
> >   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).

Looks like it makes sense to match ZEN2 flag and specific BIOS version.  That will cover the broken BIOS and CPU.


>
> > +           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"

Made suggestions to v5.

>
> > +           return 1;
> > +   }
> > +
> > +
>
> Only need one newline needed here.

Fixed in V5.

Thanks for the review comments!

Perry.

>
> > +   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 */