Re: [PATCH v5 08/22] cpufreq: amd: introduce the support for the processors with shared memory solution

[Huang Rui <ray.huang@amd.com>]

On Fri, Dec 17, 2021 at 02:04:11AM +0800, Rafael J. Wysocki wrote:
> On Tue, Nov 30, 2021 at 1:38 PM Huang Rui <ray.huang@amd.com> wrote:
> >
> > In some of Zen2 and Zen3 based processors, they are using the shared
> > memory that exposed from ACPI SBIOS. In this kind of the processors,
> > there is no MSR support, so we add acpi cppc function as the backend for
> > them.
> >
> > It is using a module param (shared_mem) to enable related processors
> > manually. We will enable this by default once we address performance
> > issue on this solution.
> >
> > Signed-off-by: Jinzhou Su <Jinzhou.Su@amd.com>
> > Signed-off-by: Huang Rui <ray.huang@amd.com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 72 ++++++++++++++++++++++++++++++++++--
> >  1 file changed, 68 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index cab266b8bf35..68991c450fd5 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -35,6 +35,19 @@
> >  #define AMD_PSTATE_TRANSITION_LATENCY  0x20000
> >  #define AMD_PSTATE_TRANSITION_DELAY    500
> >
> > +/* TODO: We need more time to fine tune processors with shared memory solution
> > + * with community together.
> > + *
> > + * There are some performance drops on the CPU benchmarks which reports from
> > + * Suse. We are co-working with them to fine tune the shared memory solution. So
> > + * we disable it by default to go acpi-cpufreq on these processors and add a
> > + * module parameter to be able to enable it manually for debugging.
> > + */
> > +static bool shared_mem = false;
> > +module_param(shared_mem, bool, 0444);
> > +MODULE_PARM_DESC(shared_mem,
> > +                "enable amd-pstate on processors with shared memory solution (false = disabled (default), true = enabled)");
> > +
> >  static struct cpufreq_driver amd_pstate_driver;
> >
> >  struct amd_cpudata {
> > @@ -60,6 +73,19 @@ static inline int pstate_enable(bool enable)
> >         return wrmsrl_safe(MSR_AMD_CPPC_ENABLE, enable);
> >  }
> >
> > +static int cppc_enable(bool enable)
> > +{
> > +       int cpu, ret = 0;
> > +
> > +       for_each_online_cpu(cpu) {
> > +               ret = cppc_set_enable(cpu, enable);
> > +               if (ret)
> > +                       return ret;
> > +       }
> > +
> > +       return ret;
> > +}
> > +
> >  DEFINE_STATIC_CALL(amd_pstate_enable, pstate_enable);
> >
> >  static inline int amd_pstate_enable(bool enable)
> > @@ -90,6 +116,24 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
> >         return 0;
> >  }
> >
> > +static int cppc_init_perf(struct amd_cpudata *cpudata)
> > +{
> > +       struct cppc_perf_caps cppc_perf;
> > +
> > +       int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
> > +       if (ret)
> > +               return ret;
> > +
> > +       WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf());
> > +
> > +       WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
> > +       WRITE_ONCE(cpudata->lowest_nonlinear_perf,
> > +                  cppc_perf.lowest_nonlinear_perf);
> > +       WRITE_ONCE(cpudata->lowest_perf, cppc_perf.lowest_perf);
> > +
> > +       return 0;
> > +}
> > +
> >  DEFINE_STATIC_CALL(amd_pstate_init_perf, pstate_init_perf);
> >
> >  static inline int amd_pstate_init_perf(struct amd_cpudata *cpudata)
> > @@ -107,6 +151,19 @@ static void pstate_update_perf(struct amd_cpudata *cpudata, u32 min_perf,
> >                               READ_ONCE(cpudata->cppc_req_cached));
> >  }
> >
> > +static void cppc_update_perf(struct amd_cpudata *cpudata,
> > +                            u32 min_perf, u32 des_perf,
> > +                            u32 max_perf, bool fast_switch)
> > +{
> > +       struct cppc_perf_ctrls perf_ctrls;
> > +
> > +       perf_ctrls.max_perf = max_perf;
> > +       perf_ctrls.min_perf = min_perf;
> > +       perf_ctrls.desired_perf = des_perf;
> > +
> > +       cppc_set_perf(cpudata->cpu, &perf_ctrls);
> > +}
> > +
> >  DEFINE_STATIC_CALL(amd_pstate_update_perf, pstate_update_perf);
> >
> >  static inline void amd_pstate_update_perf(struct amd_cpudata *cpudata,
> > @@ -326,7 +383,8 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> >         /* It will be updated by governor */
> >         policy->cur = policy->cpuinfo.min_freq;
> >
> > -       policy->fast_switch_possible = true;
> > +       if (boot_cpu_has(X86_FEATURE_CPPC))
> > +               policy->fast_switch_possible = true;
> >
> >         ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0],
> >                                    FREQ_QOS_MIN, policy->cpuinfo.min_freq);
> > @@ -376,7 +434,6 @@ static struct cpufreq_driver amd_pstate_driver = {
> >         .flags          = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
> >         .verify         = amd_pstate_verify,
> >         .target         = amd_pstate_target,
> > -       .adjust_perf    = amd_pstate_adjust_perf,
> >         .init           = amd_pstate_cpu_init,
> >         .exit           = amd_pstate_cpu_exit,
> >         .name           = "amd-pstate",
> > @@ -399,8 +456,15 @@ static int __init amd_pstate_init(void)
> >                 return -EEXIST;
> >
> >         /* capability check */
> > -       if (!boot_cpu_has(X86_FEATURE_CPPC)) {
> > -               pr_debug("AMD CPPC MSR based functionality is not supported\n");
> > +       if (boot_cpu_has(X86_FEATURE_CPPC)) {
> > +               pr_debug("AMD CPPC MSR based functionality is supported\n");
> > +               amd_pstate_driver.adjust_perf = amd_pstate_adjust_perf;
> > +       } else if (shared_mem) {
> > +               static_call_update(amd_pstate_enable, cppc_enable);
> > +               static_call_update(amd_pstate_init_perf, cppc_init_perf);
> > +               static_call_update(amd_pstate_update_perf, cppc_update_perf);
> 
> I would rather add the static call definitions in this patch,
> otherwise is somewhat cumbersome to review the series.
> 

I see. Will move them into this patch in V6.

Thanks,
Ray

> > +       } else {
> > +               pr_info("This processor supports shared memory solution, you can enable it with amd_pstate.shared_mem=1\n");
> >                 return -ENODEV;
> >         }
> >
> > --
> > 2.25.1
> >