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

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Ray,


> -----Original Message-----
> From: Huang, Ray <Ray.Huang@xxxxxxx>
> Sent: Monday, April 15, 2024 11:16 PM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> Cc: rafael.j.wysocki@xxxxxxxxx; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; viresh.kumar@xxxxxxxxxx; Shenoy, Gautham
> Ranjal <gautham.shenoy@xxxxxxx>; Petkov, Borislav
> <Borislav.Petkov@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Huang, Shimmer <Shimmer.Huang@xxxxxxx>;
> oleksandr@xxxxxxxxxxxxxx; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng, Li
> (Jassmine) <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v10 8/8] cpufreq: amd-pstate: Add quirk for the pstate CPPC
> capabilities missing
>
> 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

In general, if the `quirks` variable is dynamically allocated during the driver's execution, it should be freed during the driver's uninstallation to avoid memory leaks. If it is a static or constant variable, it does not need to be explicitly freed.
In this patch, quirks is used to store the pointer to  "dmi->driver_data",  I will add your ack flag for this patch if you have no concern for this.

+       quirks = dmi->driver_data;

Perry.

>
> >
> >  /*
> >   * 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
> >