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(host109-154-46-208.range109-154.btcentralplus.com. [109.154.46.208]) by smtp.gmail.com with ESMTPSA id k7-20020a7bc407000000b004126e26f756sm220756wmi.43.2024.02.27.15.34.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Feb 2024 15:34:57 -0800 (PST) From: Qais Yousef To: "Rafael J. Wysocki" , Viresh Kumar Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , "Pierre Gondois" , Qais Yousef , Pierre Gondois Subject: [PATCH] cpufreq: Honour transition_latency over transition_delay_us Date: Tue, 27 Feb 2024 23:34:52 +0000 Message-Id: <20240227233452.405852-1-qyousef@layalina.io> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240222233947.sl435tvhhpe5iqzw@airbuntu> References: <20240222233947.sl435tvhhpe5iqzw@airbuntu> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Some platforms like Arm's Juno can have a high transition latency that can be larger than the 2ms cap introduced. If a driver report a transition_latency that is higher than the cap, then use it as-is. Update comment s/10/2/ to reflect the new cap of 2ms. Reported-by: Pierre Gondois Signed-off-by: Qais Yousef --- drivers/cpufreq/cpufreq.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 66cef33c4ec7..926a51cb7e52 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -576,8 +576,17 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy) latency = policy->cpuinfo.transition_latency / NSEC_PER_USEC; if (latency) { + unsigned int max_delay_us = 2 * MSEC_PER_SEC; + + /* + * If the platform already has high transition_latency, use it + * as-is. + */ + if (latency > max_delay_us) + return latency; + /* - * For platforms that can change the frequency very fast (< 10 + * For platforms that can change the frequency very fast (< 2 * us), the above formula gives a decent transition delay. But * for platforms where transition_latency is in milliseconds, it * ends up giving unrealistic values. @@ -586,7 +595,7 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy) * a reasonable amount of time after which we should reevaluate * the frequency. */ - return min(latency * LATENCY_MULTIPLIER, (unsigned int)(2 * MSEC_PER_SEC)); + return min(latency * LATENCY_MULTIPLIER, max_delay_us); } return LATENCY_MULTIPLIER;