RE: [PATCH V3 3/7] cpufreq: amd-pstate: Enable AMD Pstate Preferred Core Supporting.

From: Meng, Li (Jassmine)
Date: Thu Aug 24 2023 - 21:59:28 EST

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[AMD Official Use Only - General]

Hello Wyes:

> -----Original Message-----
> From: Karny, Wyes <Wyes.Karny@xxxxxxx>
> Sent: Thursday, August 24, 2023 2:48 PM
> To: Meng, Li (Jassmine) <Li.Meng@xxxxxxx>
> Cc: Karny, Wyes <Wyes.Karny@xxxxxxx>; Rafael J . Wysocki
> <rafael.j.wysocki@xxxxxxxxx>; Huang, Ray <Ray.Huang@xxxxxxx>; linux-
> pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; linux-
> acpi@xxxxxxxxxxxxxxx; Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>; linux-
> kselftest@xxxxxxxxxxxxxxx; Fontenot, Nathan
> <Nathan.Fontenot@xxxxxxx>; Sharma, Deepak
> <Deepak.Sharma@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Yuan, Perry <Perry.Yuan@xxxxxxx>; Du,
> Xiaojian <Xiaojian.Du@xxxxxxx>; Viresh Kumar <viresh.kumar@xxxxxxxxxx>;
> Borislav Petkov <bp@xxxxxxxxx>
> Subject: Re: [PATCH V3 3/7] cpufreq: amd-pstate: Enable AMD Pstate
> Preferred Core Supporting.
>
> Hi Meng Li,
>
> On 24 Aug 10:12, Meng Li wrote:
> > AMD Pstate driver utilizes the functions and data structures provided
> > by the ITMT architecture to enable the scheduler to favor scheduling
> > on cores which can be get a higher frequency with lower voltage. We
> > call it AMD Pstate Preferrred Core.
> >
> > Here sched_set_itmt_core_prio() is called to set priorities and
> > sched_set_itmt_support() is called to enable ITMT feature.
> > AMD Pstate driver uses the highest performance value to indicate the
> > priority of CPU. The higher value has a higher priority.
> >
> > The initial core rankings are set up by AMD Pstate when the system
> > boots.
> >
> > Add device attribute for preferred core states.
> >
> > Add one new early parameter `enable` to allow user to enable the
> > preferred core if the processor and power firmware can support
> > preferred core feature.
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > Co-developed-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > Signed-off-by: Meng Li <li.meng@xxxxxxx>
> > Co-developed-by: Meng Li <li.meng@xxxxxxx>
> > Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> > drivers/cpufreq/amd-pstate.c | 120
> > ++++++++++++++++++++++++++++++-----
> > 1 file changed, 104 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 9a1e194d5cf8..d02305675f66 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -37,6 +37,7 @@
> > #include <linux/uaccess.h>
> > #include <linux/static_call.h>
> > #include <linux/amd-pstate.h>
> > +#include <linux/topology.h>
> >
> > #include <acpi/processor.h>
> > #include <acpi/cppc_acpi.h>
> > @@ -49,6 +50,8 @@
> >
> > #define AMD_PSTATE_TRANSITION_LATENCY 20000
> > #define AMD_PSTATE_TRANSITION_DELAY 1000
> > +#define AMD_PSTATE_PREFCORE_THRESHOLD 166
> > +#define AMD_PSTATE_MAX_CPPC_PERF 255
> >
> > /*
> > * TODO: We need more time to fine tune processors with shared memory
> > solution @@ -65,6 +68,9 @@ static struct cpufreq_driver
> > amd_pstate_epp_driver; static int cppc_state =
> AMD_PSTATE_UNDEFINED;
> > static bool cppc_enabled;
> >
> > +/*Preferred Core featue is supported*/ static bool prefcore = true;
> > +
> > /*
> > * AMD Energy Preference Performance (EPP)
> > * The EPP is used in the CCLK DPM controller to drive @@ -290,23
> > +296,21 @@ static inline int amd_pstate_enable(bool enable) static
> > int pstate_init_perf(struct amd_cpudata *cpudata) {
> > u64 cap1;
> > - u32 highest_perf;
> >
> > int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
> > &cap1);
> > if (ret)
> > return ret;
> >
> > - /*
> > - * TODO: Introduce AMD specific power feature.
> > - *
> > - * CPPC entry doesn't indicate the highest performance in some
> ASICs.
> > + /* For platforms that do not support the preferred core feature, the
> > + * highest_pef may be configured with 166 or 255, to avoid max
> frequency
> > + * calculated wrongly. we take the AMD_CPPC_HIGHEST_PERF(cap1)
> value as
> > + * the default max perf.
> > */
> > - highest_perf = amd_get_highest_perf();
> > - if (highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
> > - highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);
> > -
> > - WRITE_ONCE(cpudata->highest_perf, highest_perf);
> > + if (prefcore)
> > + WRITE_ONCE(cpudata->highest_perf,
> AMD_PSTATE_PREFCORE_THRESHOLD);
> > + else
> > + WRITE_ONCE(cpudata->highest_perf,
> AMD_CPPC_HIGHEST_PERF(cap1));
>
> Can we disable `preferred core` in HW? If not then when we disable
> `preferred core` in software (via the cmd line param you have created), HW
> still gives core ranking through highest perf register/MSR. So, we have to
> filter the core ranking info form the highest perf register/MSR and set
> cpudata->highest_perf accordingly. IMO we should have two variables, one
> which indicated HW support and other one which indicates SW overwrite. In
> this function we should be checking only HW support.
>
[Meng, Li (Jassmine)]
We use one variable 'prefcore' to check whether the `preferred core` is supported.
When either HW or SW does not support `preferred core`, it will be set to false.
When 'highest_perf' is 255, it indicates that HW does not support `preferred core`.

> >
> > WRITE_ONCE(cpudata->nominal_perf,
> AMD_CPPC_NOMINAL_PERF(cap1));
> > WRITE_ONCE(cpudata->lowest_nonlinear_perf,
> > AMD_CPPC_LOWNONLIN_PERF(cap1)); @@ -318,17 +322,15 @@ static int
> > pstate_init_perf(struct amd_cpudata *cpudata) static int
> > cppc_init_perf(struct amd_cpudata *cpudata) {
> > struct cppc_perf_caps cppc_perf;
> > - u32 highest_perf;
> >
> > int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
> > if (ret)
> > return ret;
> >
> > - highest_perf = amd_get_highest_perf();
> > - if (highest_perf > cppc_perf.highest_perf)
> > - highest_perf = cppc_perf.highest_perf;
> > -
> > - WRITE_ONCE(cpudata->highest_perf, highest_perf);
> > + if (prefcore)
> > + WRITE_ONCE(cpudata->highest_perf,
> AMD_PSTATE_PREFCORE_THRESHOLD);
> > + else
> > + WRITE_ONCE(cpudata->highest_perf,
> cppc_perf.highest_perf);
>
> Here also we should be checking only HW support.
>
> >
> > WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
> > WRITE_ONCE(cpudata->lowest_nonlinear_perf,
> > @@ -676,6 +678,72 @@ static void amd_perf_ctl_reset(unsigned int cpu)
> > wrmsrl_on_cpu(cpu, MSR_AMD_PERF_CTL, 0); }
> >
> > +/*
> > + * Set AMD Pstate Preferred Core enable can't be done directly from
> > +cpufreq callbacks
> > + * due to locking, so queue the work for later.
> > + */
> > +static void amd_pstste_sched_prefcore_workfn(struct work_struct
> > +*work) {
> > + sched_set_itmt_support();
> > +}
> > +static DECLARE_WORK(sched_prefcore_work,
> > +amd_pstste_sched_prefcore_workfn);
> > +
> > +/**
> > + * Get the highest performance register value.
> > + * @cpu: CPU from which to get highest performance.
> > + * @highest_perf: Return address.
> > + *
> > + * Return: 0 for success, -EIO otherwise.
> > + */
> > +static int amd_pstate_get_highest_perf(int cpu, u64 *highest_perf) {
> > + int ret;
> > +
> > + if (boot_cpu_has(X86_FEATURE_CPPC)) {
> > + u64 cap1;
> > +
> > + ret = rdmsrl_safe_on_cpu(cpu, MSR_AMD_CPPC_CAP1, &cap1);
> > + if (ret)
> > + return ret;
> > + WRITE_ONCE(*highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
> > + } else {
> > + ret = cppc_get_highest_perf(cpu, highest_perf);
> > + }
> > +
> > + return (ret);
> > +}
> > +
> > +static void amd_pstate_init_prefcore(void) {
> > + int cpu, ret;
> > + u64 highest_perf;
> > +
> > + if (!prefcore)
> > + return;
> > +
> > + for_each_online_cpu(cpu) {
> > + ret = amd_pstate_get_highest_perf(cpu, &highest_perf);
> > + if (ret)
> > + break;
> > +
> > + sched_set_itmt_core_prio(highest_perf, cpu);
> > +
> > + /* check if CPPC preferred core feature is enabled*/
> > + if (highest_perf == AMD_PSTATE_MAX_CPPC_PERF) {
> > + prefcore = false;
> > + return;
>
> 255 is a valid core ranking right?
>
> Thanks & Regards,
> Wyes
>
> > + }
> > + }
> > +
> > + /*
> > + * This code can be run during CPU online under the
> > + * CPU hotplug locks, so sched_set_amd_prefcore_support()
> > + * cannot be called from here. Queue up a work item
> > + * to invoke it.
> > + */
> > + schedule_work(&sched_prefcore_work);
> > +}
> > +
> > static int amd_pstate_cpu_init(struct cpufreq_policy *policy) {
> > int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
> @@
> > -1037,6 +1105,12 @@ static ssize_t status_store(struct device *a, struct
> device_attribute *b,
> > return ret < 0 ? ret : count;
> > }
> >
> > +static ssize_t prefcore_show(struct device *dev,
> > + struct device_attribute *attr, char *buf) {
> > + return sysfs_emit(buf, "%s\n", prefcore ? "enabled" : "disabled"); }
> > +
> > cpufreq_freq_attr_ro(amd_pstate_max_freq);
> > cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
> >
> > @@ -1044,6 +1118,7 @@ cpufreq_freq_attr_ro(amd_pstate_highest_perf);
> > 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 struct freq_attr *amd_pstate_attr[] = {
> > &amd_pstate_max_freq,
> > @@ -1063,6 +1138,7 @@ static struct freq_attr *amd_pstate_epp_attr[] =
> > {
> >
> > static struct attribute *pstate_global_attributes[] = {
> > &dev_attr_status.attr,
> > + &dev_attr_prefcore.attr,
> > NULL
> > };
> >
> > @@ -1506,6 +1582,8 @@ static int __init amd_pstate_init(void)
> > }
> > }
> >
> > + amd_pstate_init_prefcore();
> > +
> > return ret;
> >
> > global_attr_free:
> > @@ -1527,7 +1605,17 @@ static int __init amd_pstate_param(char *str)
> >
> > return amd_pstate_set_driver(mode_idx); }
> > +
> > +static int __init amd_prefcore_param(char *str) {
> > + if (!strcmp(str, "disable"))
> > + prefcore = false;
> > +
> > + return 0;
> > +}
> > +
> > early_param("amd_pstate", amd_pstate_param);
> > +early_param("amd_prefcore", amd_prefcore_param);
> >
> > MODULE_AUTHOR("Huang Rui <ray.huang@xxxxxxx>");
> > MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");
> > --
> > 2.34.1
> >

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In reply to: Wyes Karny: "Re: [PATCH V3 3/7] cpufreq: amd-pstate: Enable AMD Pstate Preferred Core Supporting."
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