From: Valentin Schneider <valentin.schneider@arm.com>
To: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: alexandre.torgue@st.com, rjw@rjwysocki.net,
linux-kernel@vger.kernel.org, mcoquelin.stm32@gmail.com,
hugues.fruchet@st.com, mchehab@kernel.org,
linux-stm32@st-md-mailman.stormreply.com,
linux-arm-kernel@lists.infradead.org,
linux-media@vger.kernel.org
Subject: Re: [PATCH v2 2/3] media: stm32-dcmi: Set minimum cpufreq requirement
Date: Wed, 03 Jun 2020 16:25:01 +0100 [thread overview]
Message-ID: <jhjk10oi33m.mognet@arm.com> (raw)
In-Reply-To: <20200603124559.22652-3-benjamin.gaignard@st.com>
On 03/06/20 13:45, Benjamin Gaignard wrote:
> +static void dcmi_set_min_frequency(struct stm32_dcmi *dcmi, u64 freq)
> +{
> + struct cpufreq_policy *p;
> + int cpu;
> +
> + for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
> + p = per_cpu(policy, cpu);
> + if (!p)
> + continue;
> +
> + freq_qos_update_request(&per_cpu(qos_req, cpu), freq);
> + }
> +}
> +
You may want to use a "visited" cpumask as I suggested in the previous
thread, since a policy can cover more than one CPU (IOW, a frequency domain
can span more than one CPU). It's not required per-se, AFAICT, but it makes
things a bit neater.
I also think you'll have to use the affinity notifier
(irq_set_affinity_notifier()), since AFAICT userspace can change the
affinity of that IRQ. I suppose you'll want something like:
- Check if we currently are in streaming mode
- Clear the QoS request for CPUs that were previously boosted but that
aren't in the new mask
- Add the request for the new CPUs.
You'll probably need serialize the reading of the mask in the regular
dcmi_set_min_frequency() as well. I concur all of that is somewhat
annoying, but AFAICT that's required for a sturdy implementation.
> static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
> {
> struct stm32_dcmi *dcmi = vb2_get_drv_priv(vq);
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WARNING: multiple messages have this Message-ID (diff)
From: Valentin Schneider <valentin.schneider@arm.com>
To: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: hugues.fruchet@st.com, mchehab@kernel.org,
mcoquelin.stm32@gmail.com, alexandre.torgue@st.com,
linux-media@vger.kernel.org,
linux-stm32@st-md-mailman.stormreply.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, vincent.guittot@linaro.org,
rjw@rjwysocki.net
Subject: Re: [PATCH v2 2/3] media: stm32-dcmi: Set minimum cpufreq requirement
Date: Wed, 03 Jun 2020 16:25:01 +0100 [thread overview]
Message-ID: <jhjk10oi33m.mognet@arm.com> (raw)
In-Reply-To: <20200603124559.22652-3-benjamin.gaignard@st.com>
On 03/06/20 13:45, Benjamin Gaignard wrote:
> +static void dcmi_set_min_frequency(struct stm32_dcmi *dcmi, u64 freq)
> +{
> + struct cpufreq_policy *p;
> + int cpu;
> +
> + for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) {
> + p = per_cpu(policy, cpu);
> + if (!p)
> + continue;
> +
> + freq_qos_update_request(&per_cpu(qos_req, cpu), freq);
> + }
> +}
> +
You may want to use a "visited" cpumask as I suggested in the previous
thread, since a policy can cover more than one CPU (IOW, a frequency domain
can span more than one CPU). It's not required per-se, AFAICT, but it makes
things a bit neater.
I also think you'll have to use the affinity notifier
(irq_set_affinity_notifier()), since AFAICT userspace can change the
affinity of that IRQ. I suppose you'll want something like:
- Check if we currently are in streaming mode
- Clear the QoS request for CPUs that were previously boosted but that
aren't in the new mask
- Add the request for the new CPUs.
You'll probably need serialize the reading of the mask in the regular
dcmi_set_min_frequency() as well. I concur all of that is somewhat
annoying, but AFAICT that's required for a sturdy implementation.
> static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
> {
> struct stm32_dcmi *dcmi = vb2_get_drv_priv(vq);
next prev parent reply other threads:[~2020-06-03 15:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 12:45 [PATCH v2 0/3] DCMI set minimum cpufreq requirement Benjamin Gaignard
2020-06-03 12:45 ` Benjamin Gaignard
2020-06-03 12:45 ` [PATCH v2 1/3] dt-bindings: media: stm32-dcmi: Add DCMI min frequency property Benjamin Gaignard
2020-06-03 12:45 ` Benjamin Gaignard
2020-06-03 12:45 ` [PATCH v2 2/3] media: stm32-dcmi: Set minimum cpufreq requirement Benjamin Gaignard
2020-06-03 12:45 ` Benjamin Gaignard
2020-06-03 15:25 ` Valentin Schneider [this message]
2020-06-03 15:25 ` Valentin Schneider
2020-06-03 12:45 ` [PATCH v2 3/3] ARM: dts: stm32: Set DCMI frequency requirement for stm32mp15x Benjamin Gaignard
2020-06-03 12:45 ` Benjamin Gaignard
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