From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7D47C433E0 for ; Fri, 5 Jun 2020 12:06:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C88B3206A2 for ; Fri, 5 Jun 2020 12:06:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726541AbgFEMGH (ORCPT ); Fri, 5 Jun 2020 08:06:07 -0400 Received: from foss.arm.com ([217.140.110.172]:54228 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726054AbgFEMGH (ORCPT ); Fri, 5 Jun 2020 08:06:07 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB6C12B; Fri, 5 Jun 2020 05:06:06 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 235B53F305; Fri, 5 Jun 2020 05:06:05 -0700 (PDT) References: <20200604123932.20512-1-benjamin.gaignard@st.com> <20200604123932.20512-3-benjamin.gaignard@st.com> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Benjamin Gaignard 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 v3 2/3] media: stm32-dcmi: Set minimum cpufreq requirement In-reply-to: <20200604123932.20512-3-benjamin.gaignard@st.com> Date: Fri, 05 Jun 2020 13:05:59 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/06/20 13:39, Benjamin Gaignard wrote: > Before start streaming set cpufreq minimum frequency requirement. > The cpufreq governor will adapt the frequencies and we will have > no latency for handling interrupts. > The frequency requirement is retrieved from the device-tree node. > > While streaming be notified if the IRQ affinity change thanks to > irq_affinity_notify callback. > > Signed-off-by: Benjamin Gaignard > --- > version 3: > - add a cpumask field to track boosted CPUs > - add irq_affinity_notify callback > - protect cpumask field with a mutex > > drivers/media/platform/stm32/stm32-dcmi.c | 187 ++++++++++++++++++++++++++++-- > 1 file changed, 179 insertions(+), 8 deletions(-) > > diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c > index b8931490b83b..fb6ab09eaff0 100644 > --- a/drivers/media/platform/stm32/stm32-dcmi.c > +++ b/drivers/media/platform/stm32/stm32-dcmi.c > +static void dcmi_irq_notifier_notify(struct irq_affinity_notify *notify, > + const cpumask_t *mask) > +{ > + struct stm32_dcmi *dcmi = container_of(notify, > + struct stm32_dcmi, > + notify); > + struct cpufreq_policy *p; > + int cpu; > + > + mutex_lock(&dcmi->freq_lock); > + /* > + * For all boosted CPUs check if it is still the case > + * if not remove the request > + */ > + for_each_cpu(cpu, dcmi->boosted) { > + if (cpumask_test_cpu(cpu, mask)) > + continue; > + > + p = cpufreq_cpu_get(cpu); > + if (!p) > + continue; > + > + freq_qos_remove_request(&per_cpu(qos_req, cpu)); > + cpumask_andnot(dcmi->boosted, dcmi->boosted, p->cpus); > + > + cpufreq_cpu_put(p); > + } > + > + /* > + * For CPUs in the mask check if they are boosted if not add > + * a request > + */ > + for_each_cpu(cpu, mask) { > + if (cpumask_test_cpu(cpu, dcmi->boosted)) > + continue; > + > + p = cpufreq_cpu_get(cpu); > + if (!p) > + continue; > + > + freq_qos_add_request(&p->constraints, &per_cpu(qos_req, cpu), > + FREQ_QOS_MIN, dcmi->min_frequency); > + cpumask_or(dcmi->boosted, dcmi->boosted, p->cpus); > + cpufreq_cpu_put(p); > + } > + > + mutex_unlock(&dcmi->freq_lock); That looks about right. > +} > + > +static void dcmi_irq_notifier_release(struct kref *ref) > +{ > + /* > + * This is required by affinity notifier. We don't have anything to > + * free here. > + */ > +} > + > +static void dcmi_get_cpu_policy(struct stm32_dcmi *dcmi) > +{ > + struct cpufreq_policy *p; > + int cpu; > + > + if (!alloc_cpumask_var(&dcmi->boosted, GFP_KERNEL)) > + return; I think you want to actually return i.e. -ENOMEM and do cleanups in the probe; otherwise you'll silently continue. > + > + mutex_lock(&dcmi->freq_lock); > + > + for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) { When I suggested serialization, I was thinking we may want to use the irq's desc lock to prevent the affinity from moving under our feet. Something like: CPU A CPU B for_each_cpu(cpu, mask) cpu = cpumask_next(cpu, mask) // ... cpumask_copy(desc->irq_common_data.affinity, mask) cpu = cpumask_next(cpu, mask) Now, should that happen, we would still queue the notifier and run it shortly after - and since you track which CPUs are boosted, I don't think we have any loss of information here. We may have yet another affinity change while the notifier is still queued; but the notifier boilerplate does grab the desc lock, so I think it's all good - it wasn't all super obvious so I figured I'd still point it out. > + if (cpumask_test_cpu(cpu, dcmi->boosted)) > + continue; > + > + p = cpufreq_cpu_get(cpu); > + if (!p) > + continue; > + > + freq_qos_add_request(&p->constraints, &per_cpu(qos_req, cpu), > + FREQ_QOS_MIN, FREQ_QOS_MIN_DEFAULT_VALUE); > + > + cpumask_or(dcmi->boosted, dcmi->boosted, p->cpus); > + > + cpufreq_cpu_put(p); > + } > + > + mutex_unlock(&dcmi->freq_lock); > +} > + > +static void dcmi_put_cpu_policy(struct stm32_dcmi *dcmi) > +{ > + struct cpufreq_policy *p; > + int cpu; > + > + mutex_lock(&dcmi->freq_lock); > + > + for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) { > + if (!cpumask_test_cpu(cpu, dcmi->boosted)) > + continue; > + > + p = cpufreq_cpu_get(cpu); > + if (!p) > + continue; > + > + freq_qos_remove_request(&per_cpu(qos_req, cpu)); > + cpumask_andnot(dcmi->boosted, dcmi->boosted, p->cpus); > + > + cpufreq_cpu_put(p); > + } > + > + free_cpumask_var(dcmi->boosted); > + > + mutex_unlock(&dcmi->freq_lock); > +} > + > +static void dcmi_set_min_frequency(struct stm32_dcmi *dcmi, s32 freq) > +{ > + struct irq_affinity_notify *notify = &dcmi->notify; > + int cpu; > + > + mutex_lock(&dcmi->freq_lock); > + > + for_each_cpu(cpu, irq_get_affinity_mask(dcmi->irq)) { > + if (!cpumask_test_cpu(cpu, dcmi->boosted)) > + continue; > + If the affinity changed between say .probe() and .start_streaming(), IIUC you may skip CPUs here - and even if you initialize the notifier earlier in the function (see below), that won't help you. I think dcmi_irq_notifier_notify() does almost all you want, if it also did the QoS update for CPUs that weren't affected by the affinity change, you may be able to just do: dcmi_irq_notifier_notify(irq_get_affinity_mask(dcmi->irq)); Or something along those lines. > + if (!freq_qos_request_active(&per_cpu(qos_req, cpu))) > + continue; > + > + freq_qos_update_request(&per_cpu(qos_req, cpu), freq); > + } > + > + mutex_unlock(&dcmi->freq_lock); > + > + if (freq != FREQ_QOS_MIN_DEFAULT_VALUE) {