From: Valentin Schneider <valentin.schneider@arm.com> To: Benjamin GAIGNARD <benjamin.gaignard@st.com> Cc: Hugues FRUCHET <hugues.fruchet@st.com>, "mchehab\@kernel.org" <mchehab@kernel.org>, "mcoquelin.stm32\@gmail.com" <mcoquelin.stm32@gmail.com>, Alexandre TORGUE <alexandre.torgue@st.com>, "linux-media\@vger.kernel.org" <linux-media@vger.kernel.org>, "linux-stm32\@st-md-mailman.stormreply.com" <linux-stm32@st-md-mailman.stormreply.com>, "linux-arm-kernel\@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>, "vincent.guittot\@linaro.org" <vincent.guittot@linaro.org>, "rjw\@rjwysocki.net" <rjw@rjwysocki.net> Subject: Re: [PATCH] media: stm32-dcmi: Set minimum cpufreq requirement Date: Tue, 02 Jun 2020 14:35:31 +0100 [thread overview] Message-ID: <jhjo8q1io9o.mognet@arm.com> (raw) In-Reply-To: <f95ce45f-7a1c-0feb-afa8-203ddb500f2f@st.com> On 02/06/20 12:37, Benjamin GAIGNARD wrote: > On 6/2/20 11:31 AM, Valentin Schneider wrote: >>> @@ -99,6 +100,8 @@ enum state { >>> >>> #define OVERRUN_ERROR_THRESHOLD 3 >>> >>> +#define DCMI_MIN_FREQ 650000 /* in KHz */ >>> + >> This assumes the handling part is guaranteed to always run on the same CPU >> with the same performance profile (regardless of the platform). If that's >> not guaranteed, it feels like you'd want this to be configurable in some >> way. > Yes I could add a st,stm32-dcmi-min-frequency (in KHz) parameter the > device tree node. > Something like that - I'm not sure how well this fits with the DT landscape, as you could argue it isn't really a description of the hardware, more of a description of the performance expectations of the software. I won't really argue here. >> >>> struct dcmi_graph_entity { >>> struct v4l2_async_subdev asd; >>> >> [...] >>> @@ -2020,6 +2042,8 @@ static int dcmi_probe(struct platform_device *pdev) >>> goto err_cleanup; >>> } >>> >>> + dcmi->policy = cpufreq_cpu_get(0); >>> + >> Ideally you'd want to fetch the policy of the CPU your IRQ (and handling >> thread) is affined to; The only compatible DTS I found describes a single >> A7, which is somewhat limited in the affinity area... > If I move this code just before start streaming and use get_cpu(), would > it works ? > AFAIA streaming_start() is not necessarily executing on the same CPU as the one that will handle the interrupt. I was thinking you could use the IRQ's effective affinity as a hint of which CPU(s) to boost, i.e. something like: --- struct cpumask_var_t visited; struct irq_data *d = irq_get_irq_data(irq); err = alloc_cpumask_var(visited, GFP_KERNEL); /* ... */ for_each_cpu(cpu, irq_data_get_effective_affinity_mask(d)) { /* check if not already spanned */ if (cpumask_test_cpu(cpu, visited)) continue; policy = cpufreq_cpu_get(cpu); cpumask_or(visited, visited, policy->cpus); /* do the boost for that policy here */ /* ... */ cpufreq_cpu_put(policy); } --- That of course falls apart when hotplug gets involved, and the effective affinity changes... There's irq_set_affinity_notifier() out there, but it seems it's only about the affinity, not the effective_affinity, I'm not sure how valid it would be to query the effective_affinity in that notifier. > Benjamin >> >>> dev_info(&pdev->dev, "Probe done\n"); >>> >>> platform_set_drvdata(pdev, dcmi); >>> @@ -2049,6 +2073,9 @@ static int dcmi_remove(struct platform_device *pdev) >>> >>> pm_runtime_disable(&pdev->dev); >>> >>> + if (dcmi->policy) >>> + cpufreq_cpu_put(dcmi->policy); >>> + >>> v4l2_async_notifier_unregister(&dcmi->notifier); >>> v4l2_async_notifier_cleanup(&dcmi->notifier); >>> media_entity_cleanup(&dcmi->vdev->entity);
WARNING: multiple messages have this Message-ID (diff)
From: Valentin Schneider <valentin.schneider@arm.com> To: Benjamin GAIGNARD <benjamin.gaignard@st.com> Cc: Alexandre TORGUE <alexandre.torgue@st.com>, "rjw@rjwysocki.net" <rjw@rjwysocki.net>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "mcoquelin.stm32@gmail.com" <mcoquelin.stm32@gmail.com>, Hugues FRUCHET <hugues.fruchet@st.com>, "mchehab@kernel.org" <mchehab@kernel.org>, "linux-stm32@st-md-mailman.stormreply.com" <linux-stm32@st-md-mailman.stormreply.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-media@vger.kernel.org" <linux-media@vger.kernel.org> Subject: Re: [PATCH] media: stm32-dcmi: Set minimum cpufreq requirement Date: Tue, 02 Jun 2020 14:35:31 +0100 [thread overview] Message-ID: <jhjo8q1io9o.mognet@arm.com> (raw) In-Reply-To: <f95ce45f-7a1c-0feb-afa8-203ddb500f2f@st.com> On 02/06/20 12:37, Benjamin GAIGNARD wrote: > On 6/2/20 11:31 AM, Valentin Schneider wrote: >>> @@ -99,6 +100,8 @@ enum state { >>> >>> #define OVERRUN_ERROR_THRESHOLD 3 >>> >>> +#define DCMI_MIN_FREQ 650000 /* in KHz */ >>> + >> This assumes the handling part is guaranteed to always run on the same CPU >> with the same performance profile (regardless of the platform). If that's >> not guaranteed, it feels like you'd want this to be configurable in some >> way. > Yes I could add a st,stm32-dcmi-min-frequency (in KHz) parameter the > device tree node. > Something like that - I'm not sure how well this fits with the DT landscape, as you could argue it isn't really a description of the hardware, more of a description of the performance expectations of the software. I won't really argue here. >> >>> struct dcmi_graph_entity { >>> struct v4l2_async_subdev asd; >>> >> [...] >>> @@ -2020,6 +2042,8 @@ static int dcmi_probe(struct platform_device *pdev) >>> goto err_cleanup; >>> } >>> >>> + dcmi->policy = cpufreq_cpu_get(0); >>> + >> Ideally you'd want to fetch the policy of the CPU your IRQ (and handling >> thread) is affined to; The only compatible DTS I found describes a single >> A7, which is somewhat limited in the affinity area... > If I move this code just before start streaming and use get_cpu(), would > it works ? > AFAIA streaming_start() is not necessarily executing on the same CPU as the one that will handle the interrupt. I was thinking you could use the IRQ's effective affinity as a hint of which CPU(s) to boost, i.e. something like: --- struct cpumask_var_t visited; struct irq_data *d = irq_get_irq_data(irq); err = alloc_cpumask_var(visited, GFP_KERNEL); /* ... */ for_each_cpu(cpu, irq_data_get_effective_affinity_mask(d)) { /* check if not already spanned */ if (cpumask_test_cpu(cpu, visited)) continue; policy = cpufreq_cpu_get(cpu); cpumask_or(visited, visited, policy->cpus); /* do the boost for that policy here */ /* ... */ cpufreq_cpu_put(policy); } --- That of course falls apart when hotplug gets involved, and the effective affinity changes... There's irq_set_affinity_notifier() out there, but it seems it's only about the affinity, not the effective_affinity, I'm not sure how valid it would be to query the effective_affinity in that notifier. > Benjamin >> >>> dev_info(&pdev->dev, "Probe done\n"); >>> >>> platform_set_drvdata(pdev, dcmi); >>> @@ -2049,6 +2073,9 @@ static int dcmi_remove(struct platform_device *pdev) >>> >>> pm_runtime_disable(&pdev->dev); >>> >>> + if (dcmi->policy) >>> + cpufreq_cpu_put(dcmi->policy); >>> + >>> v4l2_async_notifier_unregister(&dcmi->notifier); >>> v4l2_async_notifier_cleanup(&dcmi->notifier); >>> media_entity_cleanup(&dcmi->vdev->entity); _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-06-02 13:35 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-27 15:16 [PATCH] media: stm32-dcmi: Set minimum cpufreq requirement Benjamin Gaignard 2020-05-27 15:16 ` Benjamin Gaignard 2020-06-02 8:29 ` Hugues FRUCHET 2020-06-02 8:29 ` Hugues FRUCHET 2020-06-02 9:31 ` Valentin Schneider 2020-06-02 9:31 ` Valentin Schneider 2020-06-02 11:37 ` Benjamin GAIGNARD 2020-06-02 11:37 ` Benjamin GAIGNARD 2020-06-02 13:35 ` Valentin Schneider [this message] 2020-06-02 13:35 ` Valentin Schneider 2020-06-03 7:34 ` Benjamin GAIGNARD 2020-06-03 7:34 ` Benjamin GAIGNARD 2020-06-03 7:50 ` Vincent Guittot 2020-06-03 7:50 ` Vincent Guittot 2020-06-03 9:41 ` Valentin Schneider 2020-06-03 9:41 ` Valentin Schneider
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