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Shenoy" Cc: Perry Yuan , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org References: <20241209185248.16301-1-mario.limonciello@amd.com> <20241209185248.16301-11-mario.limonciello@amd.com> <6ea8c643-6977-4ce2-be1e-b0b0a73e8306@amd.com> <5330c947-7bfc-4932-800e-9067a9f78470@amd.com> Content-Language: en-US From: Mario Limonciello In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SA9P223CA0012.NAMP223.PROD.OUTLOOK.COM (2603:10b6:806:26::17) To DS7PR12MB6095.namprd12.prod.outlook.com (2603:10b6:8:9c::19) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB6095:EE_|PH7PR12MB7456:EE_ X-MS-Office365-Filtering-Correlation-Id: dba28098-b0e4-4429-ca0c-08dd1ed343e8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016; 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This didnt seem logical to me and I changed >>>>> cap_perf to cpudata->max_limit_perf which gives us the value updated in scaling_max_freq. >>>>> >>>>> I think as we removed the redundant clamping code, this pre-existing issue got exposed. >>>>> The below diff fixes the issue for me. >>>>> >>>>> Please let me know your thoughts on this. >>>>> >>>>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c >>>>> index d7b1de97727a..1ac34e3f1fc5 100644 >>>>> --- a/drivers/cpufreq/amd-pstate.c >>>>> +++ b/drivers/cpufreq/amd-pstate.c >>>>> @@ -699,7 +699,7 @@ static void amd_pstate_adjust_perf(unsigned int cpu, >>>>>           if (min_perf < lowest_nonlinear_perf) >>>>>                   min_perf = lowest_nonlinear_perf; >>> here^^^ >>>>> >>>>> -       max_perf = cap_perf; >>>>> +       max_perf = cpudata->max_limit_perf; >>>>>           if (max_perf < min_perf) >>>>>                   max_perf = min_perf; >>>> >>>> With this change I think you can also drop the comparison afterwards, as an optimization right? >>> >>> Umm I think it is possible that scaling_max_freq is set to a value lower than >>> lowest_nonlinear_freq in that case this if condition would be needed (as min_perf >>> is being lower bounded at lowest_nonlinear_freq at the location highlighted above). >>> I would be okay with keeping this check in. >> >> Well this feels like a bigger problem actually - why is it forcefully bounded at lowest nonlinear freq?  Performance is going to be awful at that level > > Actually this wont necessarily deteriorate the performance, as we are just restricting > the min_perf to not go below lowest_nonlinear level. So we are actually ensuring that > the schedutil doesnt select a des_perf below lowest_nonlinear_perf. > > (hence why commit 5d9a354cf839a ("cpufreq/amd-pstate: Set the initial min_freq to lowest_nonlinear_freq") was done), Sorry re-reading I didn't get my thought out properly, I meant to say performance is going to be bad BELOW that level. We're in total agreement here. >> >> but shouldn't we "let" people go below that in passive and guided?  We do for active. > > Yes I agree, we should allow the user to set min limit in the entire frequency range, > I thought there would've been some reason for restricting this. But I dont see any > reasoning for this in the blamed commit log as well. I think one reason would be that > below lowest_nonlinear_freq we dont get real power savings. And schedutil might dip > into this lower inefficient range if we dont force bound it. OK I guess to avoid regressions let's leave it as is and do a minimal change and we can revisit lifting this restriction later after you get testing done with it to see what actually happens. > > Thanks, > Dhananjay > >> >>> >>> Also, what is the behavior if max_perf is set to a value lower than min_perf in >>> the CPPC_REQ MSR? I guess platform FW would also be smart enough to handle this >>> implicitly, but cant say for sure. >>> >> >> I would hope so too; but yeah you're right we don't know for sure. >> >>>> >>>> As this is already in superm1.git/linux-next after testing can you please send a patch relative to superm1.git/linux-next branch? >>> >>> Sure, I'll send out the patch once we finalize on the above if condition. >>> >>> Regards, >>> Dhananjay >>> >>>> >>>> Thanks! >>>> >>>>> >>>>> Thanks, >>>>> Dhananjay >>>>> >>>>>> >>>>>> Reviewed-by: Gautham R. Shenoy >>>>>> Signed-off-by: Mario Limonciello >>>>>> --- >>>>>> v2: >>>>>>    * Drop lowest_perf variable >>>>>> --- >>>>>>    drivers/cpufreq/amd-pstate.c | 28 +++++----------------------- >>>>>>    1 file changed, 5 insertions(+), 23 deletions(-) >>>>>> >>>>>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c >>>>>> index 3a3df67c096d5..dc3c45b6f5103 100644 >>>>>> --- a/drivers/cpufreq/amd-pstate.c >>>>>> +++ b/drivers/cpufreq/amd-pstate.c >>>>>> @@ -537,10 +537,6 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf, >>>>>>        u32 nominal_perf = READ_ONCE(cpudata->nominal_perf); >>>>>>        u64 value = prev; >>>>>>    -    min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf, >>>>>> -            cpudata->max_limit_perf); >>>>>> -    max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf, >>>>>> -            cpudata->max_limit_perf); >>>>>>        des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf); >>>>>>          max_freq = READ_ONCE(cpudata->max_limit_freq); >>>>>> @@ -607,7 +603,7 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy_data) >>>>>>      static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy) >>>>>>    { >>>>>> -    u32 max_limit_perf, min_limit_perf, lowest_perf, max_perf, max_freq; >>>>>> +    u32 max_limit_perf, min_limit_perf, max_perf, max_freq; >>>>>>        struct amd_cpudata *cpudata = policy->driver_data; >>>>>>          max_perf = READ_ONCE(cpudata->highest_perf); >>>>>> @@ -615,12 +611,8 @@ static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy) >>>>>>        max_limit_perf = div_u64(policy->max * max_perf, max_freq); >>>>>>        min_limit_perf = div_u64(policy->min * max_perf, max_freq); >>>>>>    -    lowest_perf = READ_ONCE(cpudata->lowest_perf); >>>>>> -    if (min_limit_perf < lowest_perf) >>>>>> -        min_limit_perf = lowest_perf; >>>>>> - >>>>>> -    if (max_limit_perf < min_limit_perf) >>>>>> -        max_limit_perf = min_limit_perf; >>>>>> +    if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) >>>>>> +        min_limit_perf = min(cpudata->nominal_perf, max_limit_perf); >>>>>>          WRITE_ONCE(cpudata->max_limit_perf, max_limit_perf); >>>>>>        WRITE_ONCE(cpudata->min_limit_perf, min_limit_perf); >>>>>> @@ -1562,28 +1554,18 @@ 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; >>>>>> -    u32 max_perf, min_perf; >>>>>>        u64 value; >>>>>>        s16 epp; >>>>>>    -    max_perf = READ_ONCE(cpudata->highest_perf); >>>>>> -    min_perf = READ_ONCE(cpudata->lowest_perf); >>>>>>        amd_pstate_update_min_max_limit(policy); >>>>>>    -    max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf, >>>>>> -            cpudata->max_limit_perf); >>>>>> -    min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf, >>>>>> -            cpudata->max_limit_perf); >>>>>>        value = READ_ONCE(cpudata->cppc_req_cached); >>>>>>    -    if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) >>>>>> -        min_perf = min(cpudata->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_MAX_PERF_MASK, cpudata->max_limit_perf); >>>>>>        value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, 0); >>>>>> -    value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf); >>>>>> +    value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, cpudata->min_limit_perf); >>>>>>          /* Get BIOS pre-defined epp value */ >>>>>>        epp = amd_pstate_get_epp(cpudata, value); >>>>> >>>> >>> >> >