RE: [PATCH v11 5/9] cpufreq: amd-pstate: implement cpb_boost sysfs entry for boost control

[Yuan, Perry]

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Friday, June 14, 2024 1:55 AM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>; Shenoy, Gautham Ranjal
> <gautham.shenoy@xxxxxxx>; Petkov, Borislav <Borislav.Petkov@xxxxxxx>
> Cc: rafael.j.wysocki@xxxxxxxxx; viresh.kumar@xxxxxxxxxx; 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 v11 5/9] cpufreq: amd-pstate: implement cpb_boost
> sysfs entry for boost control
>
> On 6/13/2024 02:25, Perry Yuan wrote:
> > From: Perry Yuan <Perry.Yuan@xxxxxxx>
> >
> > With this new sysfs entry `cpb_boost`created, user can change CPU
> > boost state dynamically under `active`, `guided` and `passive` modes.
> > And the highest perf and frequency will also be updated as the boost
> > state changing.
> >
> > 0): check current boost state
> > cat /sys/devices/system/cpu/amd_pstate/cpb_boost
> >
> > 1): disable CPU boost
> > sudo bash -c "echo 0 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
> >
> > 2): enable CPU boost
> > sudo bash -c "echo 1 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217618
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > ---
> >   drivers/cpufreq/amd-pstate-ut.c |   2 +-
> >   drivers/cpufreq/amd-pstate.c    | 117
> +++++++++++++++++++++++++++++++-
> >   drivers/cpufreq/amd-pstate.h    |   1 +
> >   3 files changed, 118 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate-ut.c
> > b/drivers/cpufreq/amd-pstate-ut.c index fc275d41d51e..b528f198f4c3
> > 100644
> > --- a/drivers/cpufreq/amd-pstate-ut.c
> > +++ b/drivers/cpufreq/amd-pstate-ut.c
> > @@ -227,7 +227,7 @@ static void amd_pstate_ut_check_freq(u32 index)
> >                     goto skip_test;
> >             }
> >
> > -           if (cpudata->boost_supported) {
> > +           if (amd_pstate_global_params.cpb_boost) {
> >                     if ((policy->max == cpudata->max_freq) ||
> >                                     (policy->max == cpudata-
> >nominal_freq))
> >                             amd_pstate_ut_cases[index].result =
> AMD_PSTATE_UT_RESULT_PASS;
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 9f42524074a9..fe7c9d3562c5 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -104,6 +104,7 @@ static bool amd_pstate_prefcore = true;
> >   static struct quirk_entry *quirks;
> >   struct amd_pstate_global_params amd_pstate_global_params;
> >   EXPORT_SYMBOL_GPL(amd_pstate_global_params);
> > +static int amd_pstate_cpu_boost(int cpu, bool state);
> >
> >   /*
> >    * AMD Energy Preference Performance (EPP) @@ -738,6 +739,7 @@
> > static int amd_pstate_boost_set(struct amd_cpudata *cpudata)
> >     if (amd_pstate_global_params.cpb_supported) {
> >             current_pstate_driver->boost_enabled = true;
> >             WRITE_ONCE(cpudata->boost_supported, true);
> > +           WRITE_ONCE(cpudata->boost_state, true);
> >     }
> >
> >     amd_pstate_global_params.cpb_boost =
> > amd_pstate_global_params.cpb_supported;
> > @@ -745,6 +747,7 @@ static int amd_pstate_boost_set(struct
> amd_cpudata
> > *cpudata)
> >
> >   exit_err:
> >     WRITE_ONCE(cpudata->boost_supported, false);
> > +   WRITE_ONCE(cpudata->boost_state, false);
> >     current_pstate_driver->boost_enabled = false;
> >     amd_pstate_global_params.cpb_boost = false;
> >     return ret;
> > @@ -1348,6 +1351,116 @@ static ssize_t prefcore_show(struct device
> *dev,
> >     return sysfs_emit(buf, "%s\n",
> str_enabled_disabled(amd_pstate_prefcore));
> >   }
> >
> > +static int amd_pstate_cpu_boost_update(struct cpufreq_policy *policy,
> > +bool on) {
> > +   struct amd_cpudata *cpudata = policy->driver_data;
> > +   struct cppc_perf_ctrls perf_ctrls;
> > +   u32 highest_perf, nominal_perf, nominal_freq, max_freq;
> > +   int ret;
> > +
> > +   if (!policy) {
> > +           pr_err("policy is null\n");
> > +           return -ENODATA;
> > +   }
>
> This is dead code that can't possibly be hit, because there would be a NULL
> pointer dereference above for this line:
>
>       struct amd_cpudata *cpudata = policy->driver_data;
>
> Furthermore, the caller for this function, amd_pstate_cpu_boost() has the
> same check already.
>
> So drop the check here.

Will improve the checking code in v12.
Thanks for the feedback.

>
> > +
> > +   highest_perf = READ_ONCE(cpudata->highest_perf);
> > +   nominal_perf = READ_ONCE(cpudata->nominal_perf);
> > +   nominal_freq = READ_ONCE(cpudata->nominal_freq);
> > +   max_freq = READ_ONCE(cpudata->max_freq);
> > +
> > +   if (boot_cpu_has(X86_FEATURE_CPPC)) {
> > +           u64 value = READ_ONCE(cpudata->cppc_req_cached);
> > +
> > +           value &= ~GENMASK_ULL(7, 0);
> > +           value |= on ? highest_perf : nominal_perf;
> > +           WRITE_ONCE(cpudata->cppc_req_cached, value);
> > +
> > +           wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> > +   } else {
> > +           perf_ctrls.max_perf = on ? highest_perf : nominal_perf;
> > +           ret = cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> > +           if (ret) {
> > +                   cpufreq_cpu_release(policy);
> > +                   pr_debug("failed to set energy perf value (%d)\n",
> ret);
> > +                   return ret;
> > +           }
> > +   }
> > +
> > +   if (on)
> > +           policy->cpuinfo.max_freq = max_freq;
> > +   else
> > +           policy->cpuinfo.max_freq = nominal_freq * 1000;
> > +
> > +   policy->max = policy->cpuinfo.max_freq;
> > +
> > +   if (cppc_state == AMD_PSTATE_PASSIVE) {
> > +           ret = freq_qos_update_request(&cpudata->req[1], policy-
> >cpuinfo.max_freq);
> > +           if (ret < 0)
> > +                   pr_debug("Failed to update freq constraint:
> CPU%d\n", cpudata->cpu);
> > +   }
> > +
> > +   return ret < 0 ? ret : 0;
> > +}
> > +
> > +static int amd_pstate_cpu_boost(int cpu, bool state) {
> > +   int ret;
> > +   struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> > +   struct amd_cpudata *cpudata = policy->driver_data;
> > +
> > +   if (!policy) {
> > +           pr_err("policy is NULL\n");
> > +           ret = -ENODATA;
> > +           goto err_exit;
> > +   }
> > +
> > +   ret = amd_pstate_cpu_boost_update(policy, state);
> > +   refresh_frequency_limits(policy);
> > +   WRITE_ONCE(cpudata->boost_state, state);
> > +   policy->boost_enabled = state;
> > +
> > +err_exit:
> > +   cpufreq_cpu_put(policy);
> > +   return ret < 0 ? ret : 0;
> > +}
> > +
> > +static ssize_t cpb_boost_show(struct device *dev,
> > +                      struct device_attribute *attr, char *buf) {
> > +   return sysfs_emit(buf, "%u\n",
> amd_pstate_global_params.cpb_boost);
> > +}
> > +
> > +static ssize_t cpb_boost_store(struct device *dev, struct device_attribute
> *b,
> > +                       const char *buf, size_t count) {
> > +   bool new_state;
> > +   ssize_t ret;
> > +   int cpu;
> > +
> > +   if (!amd_pstate_global_params.cpb_supported) {
> > +           pr_err("Boost mode is not supported by this processor or
> SBIOS\n");
> > +           return -EINVAL;
> > +   }
> > +
> > +   ret = kstrtobool(buf, &new_state);
> > +   if (ret)
> > +           return ret;
> > +
> > +   mutex_lock(&amd_pstate_driver_lock);
> > +   for_each_present_cpu(cpu) {
> > +           ret = amd_pstate_cpu_boost(cpu, new_state);
> > +           if (ret < 0) {
> > +                   pr_warn("failed to update cpu boost for CPU%d
> (%zd)\n", cpu, ret);
> > +                   goto err_exit;
> > +           }
> > +   }
> > +   amd_pstate_global_params.cpb_boost = !!new_state;
> > +
> > +err_exit:
> > +   mutex_unlock(&amd_pstate_driver_lock);
> > +   return ret < 0 ? ret : count;
> > +}
> > +
> >   cpufreq_freq_attr_ro(amd_pstate_max_freq);
> >   cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
> >
> > @@ -1358,6 +1471,7 @@
> cpufreq_freq_attr_rw(energy_performance_preference);
> >   cpufreq_freq_attr_ro(energy_performance_available_preferences);
> >   static DEVICE_ATTR_RW(status);
> >   static DEVICE_ATTR_RO(prefcore);
> > +static DEVICE_ATTR_RW(cpb_boost);
> >
> >   static struct freq_attr *amd_pstate_attr[] = {
> >     &amd_pstate_max_freq,
> > @@ -1382,6 +1496,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
> >   static struct attribute *pstate_global_attributes[] = {
> >     &dev_attr_status.attr,
> >     &dev_attr_prefcore.attr,
> > +   &dev_attr_cpb_boost.attr,
> >     NULL
> >   };
> >
> > @@ -1420,7 +1535,7 @@ static int amd_pstate_init_boost(struct
> cpufreq_policy *policy)
> >     if (ret)
> >             return ret;
> >
> > -   policy->boost_enabled = READ_ONCE(cpudata->boost_supported);
> > +   policy->boost_enabled = READ_ONCE(cpudata->boost_state);
> >
> >     return 0;
> >   }
> > diff --git a/drivers/cpufreq/amd-pstate.h
> > b/drivers/cpufreq/amd-pstate.h index 0b75a6267fca..9eba854ab7d3
> 100644
> > --- a/drivers/cpufreq/amd-pstate.h
> > +++ b/drivers/cpufreq/amd-pstate.h
> > @@ -99,6 +99,7 @@ struct amd_cpudata {
> >     u32     policy;
> >     u64     cppc_cap1_cached;
> >     bool    suspended;
> > +   bool    boost_state;
> >   };
> >
> >   /**