Messages in this thread Patch in this message | | | Subject | Re: [PATCH v4 4/5] cpufreq: qcom-cpufreq-hw: Use new thermal pressure update function | From | Thara Gopinath <> | Date | Mon, 15 Nov 2021 18:39:18 -0500 |
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On 11/15/21 3:57 PM, Thara Gopinath wrote: > > > On 11/9/21 2:57 PM, Lukasz Luba wrote: >> Thermal pressure provides a new API, which allows to use CPU frequency >> as an argument. That removes the need of local conversion to capacity. >> Use this new API and remove old local conversion code. >> >> The new arch_update_thermal_pressure() also accepts boost frequencies, >> which solves issue in the driver code with wrong reduced capacity >> calculation. The reduced capacity was calculated wrongly due to >> 'policy->cpuinfo.max_freq' used as a divider. The value present there was >> actually the boost frequency. Thus, even a normal maximum frequency value >> which corresponds to max CPU capacity (arch_scale_cpu_capacity(cpu_id)) >> is not able to remove the capping.
Also I failed to mention that, currently freq_factor is initialized as cpuinfo.max_freq / 1000 which means again all the issues you mentioned below can be hit, if some cpufreq driver decides to set boost at init. I have sent a patch earlier today to fix this.
https://lore.kernel.org/linux-arm-msm/20211115201010.68567-1-thara.gopinath@linaro.org/T/#u
-- Warm Regards Thara (She/Her/Hers) > > Yes, although cpuinfo.max_freq does not reflect the boost frequency > unless boost is enabled atleast once. I have sent a patch to fix this. > But I agree that using cpuinfo.max_freq has issues you have mentioned in > this patch if boost is enabled once. > > So, for this patch > > Reviewed-by: Thara Gopinath <thara.gopinath@linaro.org> > > Warm Regards > Thara (She/Her/Hers) >> >> The second side effect which is solved is that the reduced frequency >> wasn't >> properly translated into the right reduced capacity, >> e.g. >> boost frequency = 3000MHz (stored in policy->cpuinfo.max_freq) >> max normal frequency = 2500MHz (which is 1024 capacity) >> 2nd highest frequency = 2000MHz (which translates to 819 capacity) >> >> Then in a scenario when the 'throttled_freq' max allowed frequency was >> 2000MHz the driver translated it into 682 capacity: >> capacity = 1024 * 2000 / 3000 = 682 >> Then set the pressure value bigger than actually applied by the HW: >> max_capacity - capacity => 1024 - 682 = 342 (<- thermal pressure) >> Which was causing higher throttling and misleading task scheduler >> about available CPU capacity. >> A proper calculation in such case should be: >> capacity = 1024 * 2000 / 2500 = 819 >> 1024 - 819 = 205 (<- thermal pressure) >> >> This patch relies on the new arch_update_thermal_pressure() handling >> correctly such use case (with boost frequencies). >> >> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> >> --- >> drivers/cpufreq/qcom-cpufreq-hw.c | 15 +++------------ >> 1 file changed, 3 insertions(+), 12 deletions(-) >> >> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c >> b/drivers/cpufreq/qcom-cpufreq-hw.c >> index 0138b2ec406d..248135e5087e 100644 >> --- a/drivers/cpufreq/qcom-cpufreq-hw.c >> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c >> @@ -275,10 +275,10 @@ static unsigned int >> qcom_lmh_get_throttle_freq(struct qcom_cpufreq_data *data) >> static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data) >> { >> - unsigned long max_capacity, capacity, freq_hz, throttled_freq; >> struct cpufreq_policy *policy = data->policy; >> int cpu = cpumask_first(policy->cpus); >> struct device *dev = get_cpu_device(cpu); >> + unsigned long freq_hz, throttled_freq; >> struct dev_pm_opp *opp; >> unsigned int freq; >> @@ -295,17 +295,8 @@ static void qcom_lmh_dcvs_notify(struct >> qcom_cpufreq_data *data) >> throttled_freq = freq_hz / HZ_PER_KHZ; >> - /* Update thermal pressure */ >> - >> - max_capacity = arch_scale_cpu_capacity(cpu); >> - capacity = mult_frac(max_capacity, throttled_freq, >> policy->cpuinfo.max_freq); >> - >> - /* Don't pass boost capacity to scheduler */ >> - if (capacity > max_capacity) >> - capacity = max_capacity; >> - >> - arch_set_thermal_pressure(policy->related_cpus, >> - max_capacity - capacity); >> + /* Update thermal pressure (the boost frequencies are accepted) */ >> + arch_update_thermal_pressure(policy->related_cpus, throttled_freq); >> /* >> * In the unlikely case policy is unregistered do not enable >> >
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