From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sudeep Holla Subject: Re: [PATCH 0/2] cpufreq/opp: rework regulator initialization Date: Fri, 8 Feb 2019 11:39:04 +0000 Message-ID: <20190208113904.GB7913@e107155-lin> References: <20190207122227.19873-1-m.szyprowski@samsung.com> <20190208064957.zhyue42kpgaoslwm@vireshk-i7> <20190208103133.ysvaroyniuc3k4i5@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Viresh Kumar , Marek Szyprowski , Linux Kernel Mailing List , Linux PM , Linux Samsung SoC , "Rafael J . Wysocki" , Nishanth Menon , Stephen Boyd , Bartlomiej Zolnierkiewicz , Sudeep Holla , Dave Gerlach , Wolfram Sang List-Id: linux-pm@vger.kernel.org On Fri, Feb 08, 2019 at 11:42:20AM +0100, Rafael J. Wysocki wrote: > On Fri, Feb 8, 2019 at 11:31 AM Viresh Kumar wrote: > > > > On 08-02-19, 11:22, Rafael J. Wysocki wrote: > > > There are cpufreq driver suspend and resume callbacks, maybe use them? > > > > > > The driver could do the I2C transactions in its suspend/resume > > > callbacks and do nothing in online/offline if those are part of > > > system-wide suspend/resume. > > > > These are per-policy things that we need to do, not sure if driver > > suspend/resume is a good place for that. It is more for a case where > > CPU 0-3 are in one policy and 4-7 in another. Now 1-7 are > > hot-unplugged during system suspend and hotplugged later on. This is > > more like complete removal/addition of devices instead of > > suspend/resume. > > No, it isn't. We don't remove devices on offline. We migrate stuff > away from them and (opportunistically) power them down. > > If this is system suspend, the driver kind of knows that offline will > take place, so it can prepare for it. Likewise, when online takes > place during system-wide resume, it generally is known that this is > system-wide resume (there is a flag to indicate that in CPU hotplug), > it can be "smart" and avoid accessing suspended devices. Deferring > the frequency set up until the driver resume time should do the trick > I suppose. I agree. The reason we don't see this generally on boot is because all the CPUs are brought online before CPUfreq is initialised. While during system suspend, we call cpufreq_online which in turn calls ->init in the hotplug state machine. So as Rafael suggests we need to do some trick, but can it be done in the core itself ? I may be missing something, but how about the patch below: Regards, Sudeep -- diff --git i/drivers/cpufreq/cpufreq.c w/drivers/cpufreq/cpufreq.c index e35a886e00bc..7d8b0b99f91d 100644 --- i/drivers/cpufreq/cpufreq.c +++ w/drivers/cpufreq/cpufreq.c @@ -1241,7 +1241,8 @@ static int cpufreq_online(unsigned int cpu) policy->max = policy->user_policy.max; } - if (cpufreq_driver->get && !cpufreq_driver->setpolicy) { + if (cpufreq_driver->get && !cpufreq_driver->setpolicy && + !cpufreq_suspended) { policy->cur = cpufreq_driver->get(policy->cpu); if (!policy->cur) { pr_err("%s: ->get() failed\n", __func__); @@ -1702,6 +1703,11 @@ void cpufreq_resume(void) pr_err("%s: Failed to start governor for policy: %p\n", __func__, policy); } + policy->cur = cpufreq_driver->get(policy->cpu); + if (!policy->cur) { + pr_err("%s: ->get() failed\n", __func__); + goto out_destroy_policy; + } } }