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Message-ID: <Z1ghNdyUeosgOtdR@BLRRASHENOY1.amd.com>
Date: Tue, 10 Dec 2024 16:38:37 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Perry Yuan <perry.yuan@....com>, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org,
Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
Subject: Re: [PATCH v3 12/15] cpufreq/amd-pstate: Always write EPP value when
updating perf
On Mon, Dec 09, 2024 at 12:52:45PM -0600, Mario Limonciello wrote:
> For MSR systems the EPP value is in the same register as perf targets
> and so divding them into two separate MSR writes is wasteful.
>
> In msr_update_perf(), update both EPP and perf values in one write to
> MSR_AMD_CPPC_REQ, and cache them if successful.
>
> To accomplish this plumb the EPP value into the update_perf call and
> modify all its callers to check the return value.
>
> As this unifies calls, ensure that the MSR write is necessary before
> flushing a write out. Also drop the comparison from the passive flow
> tracing.
This version looks good as it contains all the necessary changes in
the same patch.
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
--
Thanks and Regards
gautham.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> v3:
> * Squash
> "Always write EPP value when updating perf"
> and
> "Check if CPPC request has changed before writing to the MSR or shared memory"
> * Remove extra write to cached value
> * Add comment explaining why updating two cached variables
> ---
> drivers/cpufreq/amd-pstate-trace.h | 7 +-
> drivers/cpufreq/amd-pstate.c | 108 +++++++++++++++--------------
> 2 files changed, 56 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate-trace.h b/drivers/cpufreq/amd-pstate-trace.h
> index e2221a4b6901c..8d692415d9050 100644
> --- a/drivers/cpufreq/amd-pstate-trace.h
> +++ b/drivers/cpufreq/amd-pstate-trace.h
> @@ -32,7 +32,6 @@ TRACE_EVENT(amd_pstate_perf,
> u64 aperf,
> u64 tsc,
> unsigned int cpu_id,
> - bool changed,
> bool fast_switch
> ),
>
> @@ -44,7 +43,6 @@ TRACE_EVENT(amd_pstate_perf,
> aperf,
> tsc,
> cpu_id,
> - changed,
> fast_switch
> ),
>
> @@ -57,7 +55,6 @@ TRACE_EVENT(amd_pstate_perf,
> __field(unsigned long long, aperf)
> __field(unsigned long long, tsc)
> __field(unsigned int, cpu_id)
> - __field(bool, changed)
> __field(bool, fast_switch)
> ),
>
> @@ -70,11 +67,10 @@ TRACE_EVENT(amd_pstate_perf,
> __entry->aperf = aperf;
> __entry->tsc = tsc;
> __entry->cpu_id = cpu_id;
> - __entry->changed = changed;
> __entry->fast_switch = fast_switch;
> ),
>
> - TP_printk("amd_min_perf=%lu amd_des_perf=%lu amd_max_perf=%lu freq=%llu mperf=%llu aperf=%llu tsc=%llu cpu_id=%u changed=%s fast_switch=%s",
> + TP_printk("amd_min_perf=%lu amd_des_perf=%lu amd_max_perf=%lu freq=%llu mperf=%llu aperf=%llu tsc=%llu cpu_id=%u fast_switch=%s",
> (unsigned long)__entry->min_perf,
> (unsigned long)__entry->target_perf,
> (unsigned long)__entry->capacity,
> @@ -83,7 +79,6 @@ TRACE_EVENT(amd_pstate_perf,
> (unsigned long long)__entry->aperf,
> (unsigned long long)__entry->tsc,
> (unsigned int)__entry->cpu_id,
> - (__entry->changed) ? "true" : "false",
> (__entry->fast_switch) ? "true" : "false"
> )
> );
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index d21acd961edcd..fc0eb268c0335 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -222,25 +222,47 @@ static s16 shmem_get_epp(struct amd_cpudata *cpudata)
> }
>
> static int msr_update_perf(struct amd_cpudata *cpudata, u32 min_perf,
> - u32 des_perf, u32 max_perf, bool fast_switch)
> + u32 des_perf, u32 max_perf, u32 epp, bool fast_switch)
> {
> + u64 value, prev;
> +
> + value = prev = READ_ONCE(cpudata->cppc_req_cached);
> +
> + value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
> + AMD_CPPC_DES_PERF_MASK | AMD_CPPC_EPP_PERF_MASK);
> + value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, max_perf);
> + value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, des_perf);
> + value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf);
> + value |= FIELD_PREP(AMD_CPPC_EPP_PERF_MASK, epp);
> +
> + if (value == prev)
> + return 0;
> +
> if (fast_switch) {
> - wrmsrl(MSR_AMD_CPPC_REQ, READ_ONCE(cpudata->cppc_req_cached));
> + wrmsrl(MSR_AMD_CPPC_REQ, value);
> return 0;
> + } else {
> + int ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +
> + if (ret)
> + return ret;
> }
>
> - return wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
> - READ_ONCE(cpudata->cppc_req_cached));
> + WRITE_ONCE(cpudata->cppc_req_cached, value);
> + WRITE_ONCE(cpudata->epp_cached, epp);
> +
> + return 0;
> }
>
> DEFINE_STATIC_CALL(amd_pstate_update_perf, msr_update_perf);
>
> static inline int amd_pstate_update_perf(struct amd_cpudata *cpudata,
> u32 min_perf, u32 des_perf,
> - u32 max_perf, bool fast_switch)
> + u32 max_perf, u32 epp,
> + bool fast_switch)
> {
> return static_call(amd_pstate_update_perf)(cpudata, min_perf, des_perf,
> - max_perf, fast_switch);
> + max_perf, epp, fast_switch);
> }
>
> static int msr_set_epp(struct amd_cpudata *cpudata, u32 epp)
> @@ -261,6 +283,7 @@ static int msr_set_epp(struct amd_cpudata *cpudata, u32 epp)
> return ret;
> }
>
> + /* update both so that msr_update_perf() can effectively check */
> WRITE_ONCE(cpudata->epp_cached, epp);
> WRITE_ONCE(cpudata->cppc_req_cached, value);
>
> @@ -459,12 +482,18 @@ static inline int amd_pstate_init_perf(struct amd_cpudata *cpudata)
> return static_call(amd_pstate_init_perf)(cpudata);
> }
>
> -static int shmem_update_perf(struct amd_cpudata *cpudata,
> - u32 min_perf, u32 des_perf,
> - u32 max_perf, bool fast_switch)
> +static int shmem_update_perf(struct amd_cpudata *cpudata, u32 min_perf,
> + u32 des_perf, u32 max_perf, u32 epp, bool fast_switch)
> {
> struct cppc_perf_ctrls perf_ctrls;
>
> + if (cppc_state == AMD_PSTATE_ACTIVE) {
> + int ret = shmem_set_epp(cpudata, epp);
> +
> + if (ret)
> + return ret;
> + }
> +
> perf_ctrls.max_perf = max_perf;
> perf_ctrls.min_perf = min_perf;
> perf_ctrls.desired_perf = des_perf;
> @@ -510,9 +539,7 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
> {
> unsigned long max_freq;
> struct cpufreq_policy *policy = cpufreq_cpu_get(cpudata->cpu);
> - u64 prev = READ_ONCE(cpudata->cppc_req_cached);
> u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
> - u64 value = prev;
>
> des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
>
> @@ -528,27 +555,14 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
> if (!cpudata->boost_supported)
> max_perf = min_t(unsigned long, nominal_perf, max_perf);
>
> - value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
> - AMD_CPPC_DES_PERF_MASK);
> - value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, max_perf);
> - value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, des_perf);
> - value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf);
> -
> if (trace_amd_pstate_perf_enabled() && amd_pstate_sample(cpudata)) {
> trace_amd_pstate_perf(min_perf, des_perf, max_perf, cpudata->freq,
> cpudata->cur.mperf, cpudata->cur.aperf, cpudata->cur.tsc,
> - cpudata->cpu, (value != prev), fast_switch);
> + cpudata->cpu, fast_switch);
> }
>
> - if (value == prev)
> - goto cpufreq_policy_put;
> + amd_pstate_update_perf(cpudata, min_perf, des_perf, max_perf, 0, fast_switch);
>
> - WRITE_ONCE(cpudata->cppc_req_cached, value);
> -
> - amd_pstate_update_perf(cpudata, min_perf, des_perf,
> - max_perf, fast_switch);
> -
> -cpufreq_policy_put:
> cpufreq_cpu_put(policy);
> }
>
> @@ -1544,36 +1558,24 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
> static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
> {
> struct amd_cpudata *cpudata = policy->driver_data;
> - u64 value;
> + u32 epp;
>
> amd_pstate_update_min_max_limit(policy);
>
> - value = READ_ONCE(cpudata->cppc_req_cached);
> -
> - value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
> - AMD_CPPC_DES_PERF_MASK | AMD_CPPC_EPP_PERF_MASK);
> - value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, cpudata->max_limit_perf);
> - value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, 0);
> - value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, cpudata->min_limit_perf);
> -
> if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
> - WRITE_ONCE(cpudata->epp_cached, 0);
> - value |= FIELD_PREP(AMD_CPPC_EPP_PERF_MASK, cpudata->epp_cached);
> -
> - WRITE_ONCE(cpudata->cppc_req_cached, value);
> + epp = 0;
> + else
> + epp = READ_ONCE(cpudata->epp_cached);
>
> if (trace_amd_pstate_epp_perf_enabled()) {
> - trace_amd_pstate_epp_perf(cpudata->cpu, cpudata->highest_perf,
> - cpudata->epp_cached,
> + trace_amd_pstate_epp_perf(cpudata->cpu, cpudata->highest_perf, epp,
> cpudata->min_limit_perf,
> cpudata->max_limit_perf,
> policy->boost_enabled);
> }
>
> - amd_pstate_update_perf(cpudata, cpudata->min_limit_perf, 0U,
> - cpudata->max_limit_perf, false);
> -
> - return amd_pstate_set_epp(cpudata, READ_ONCE(cpudata->epp_cached));
> + return amd_pstate_update_perf(cpudata, cpudata->min_limit_perf, 0U,
> + cpudata->max_limit_perf, epp, false);
> }
>
> static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
> @@ -1602,7 +1604,7 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
> return 0;
> }
>
> -static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
> +static int amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
> {
> u64 max_perf;
> int ret;
> @@ -1620,17 +1622,19 @@ static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
> max_perf, cpudata->boost_state);
> }
>
> - amd_pstate_update_perf(cpudata, 0, 0, max_perf, false);
> - amd_pstate_set_epp(cpudata, cpudata->epp_cached);
> + return amd_pstate_update_perf(cpudata, 0, 0, max_perf, cpudata->epp_cached, false);
> }
>
> static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
> {
> struct amd_cpudata *cpudata = policy->driver_data;
> + int ret;
>
> pr_debug("AMD CPU Core %d going online\n", cpudata->cpu);
>
> - amd_pstate_epp_reenable(cpudata);
> + ret = amd_pstate_epp_reenable(cpudata);
> + if (ret)
> + return ret;
> cpudata->suspended = false;
>
> return 0;
> @@ -1654,10 +1658,8 @@ static int amd_pstate_epp_cpu_offline(struct cpufreq_policy *policy)
> min_perf, min_perf, policy->boost_enabled);
> }
>
> - amd_pstate_update_perf(cpudata, min_perf, 0, min_perf, false);
> - amd_pstate_set_epp(cpudata, AMD_CPPC_EPP_BALANCE_POWERSAVE);
> -
> - return 0;
> + return amd_pstate_update_perf(cpudata, min_perf, 0, min_perf,
> + AMD_CPPC_EPP_BALANCE_POWERSAVE, false);
> }
>
> static int amd_pstate_epp_suspend(struct cpufreq_policy *policy)
> --
> 2.43.0
>
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