From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: schedule_timeout sleeps too long after dividing CPU frequency Date: Thu, 14 May 2015 19:29:38 +0530 Message-ID: References: <55520F0F.5010906@free.fr> <555218C7.5050602@free.fr> <20150512155004.GP2067@n2100.arm.linux.org.uk> <555380F8.5050306@free.fr> <5554858A.9010207@free.fr> <20150514115456.GB23999@linux> <55549DEE.6010202@free.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <55549DEE.6010202@free.fr> Sender: cpufreq-owner@vger.kernel.org To: Mason Cc: Russell King - ARM Linux , Daniel Lezcano , "Rafael J. Wysocki" , Mans Rullgard , Linux ARM , Linux PM , cpufreq List-Id: linux-pm@vger.kernel.org On 14 May 2015 at 18:36, Mason wrote: > When I execute "echo 18500 > scaling_max_freq" > the system is supposed to change the CPU frequency to 18.5 MHz > (I might have a bug lurking there) and PERIPHCLK is 1/2 of that, > i.e 9.25 MHz. So at least we are on the right path. But it looks to me that this call is not getting propagated well. >>From the attachment you gave initially, the event handler for twd-timers is: tick_handle_periodic(). i.e. you are running in periodic mode and not onshot... why ? > Yes, I do, but I was trying to use as much generic code as > possible to limit the chances of introducing bugs. Hmm.. > I'll take a fresh look at the ARM GLOBAL TIMER, but last I > checked, it didn't seem to handle frequency scaling. why is that required? Why will you change its freq ? The same timer is probably used for SPEAr (the platform I used to work on): http://lxr.free-electrons.com/source/arch/arm/mach-spear/time.c?v=3.14 From mboxrd@z Thu Jan 1 00:00:00 1970 From: viresh.kumar@linaro.org (Viresh Kumar) Date: Thu, 14 May 2015 19:29:38 +0530 Subject: schedule_timeout sleeps too long after dividing CPU frequency In-Reply-To: <55549DEE.6010202@free.fr> References: <55520F0F.5010906@free.fr> <555218C7.5050602@free.fr> <20150512155004.GP2067@n2100.arm.linux.org.uk> <555380F8.5050306@free.fr> <5554858A.9010207@free.fr> <20150514115456.GB23999@linux> <55549DEE.6010202@free.fr> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 14 May 2015 at 18:36, Mason wrote: > When I execute "echo 18500 > scaling_max_freq" > the system is supposed to change the CPU frequency to 18.5 MHz > (I might have a bug lurking there) and PERIPHCLK is 1/2 of that, > i.e 9.25 MHz. So at least we are on the right path. But it looks to me that this call is not getting propagated well. >>From the attachment you gave initially, the event handler for twd-timers is: tick_handle_periodic(). i.e. you are running in periodic mode and not onshot... why ? > Yes, I do, but I was trying to use as much generic code as > possible to limit the chances of introducing bugs. Hmm.. > I'll take a fresh look at the ARM GLOBAL TIMER, but last I > checked, it didn't seem to handle frequency scaling. why is that required? Why will you change its freq ? The same timer is probably used for SPEAr (the platform I used to work on): http://lxr.free-electrons.com/source/arch/arm/mach-spear/time.c?v=3.14 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: schedule_timeout sleeps too long after dividing CPU frequency Date: Thu, 14 May 2015 19:29:38 +0530 Message-ID: References: <55520F0F.5010906@free.fr> <555218C7.5050602@free.fr> <20150512155004.GP2067@n2100.arm.linux.org.uk> <555380F8.5050306@free.fr> <5554858A.9010207@free.fr> <20150514115456.GB23999@linux> <55549DEE.6010202@free.fr> Mime-Version: 1.0 Return-path: In-Reply-To: <55549DEE.6010202@free.fr> Sender: cpufreq-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mason Cc: Russell King - ARM Linux , Daniel Lezcano , "Rafael J. Wysocki" , Mans Rullgard , Linux ARM , Linux PM , cpufreq On 14 May 2015 at 18:36, Mason wrote: > When I execute "echo 18500 > scaling_max_freq" > the system is supposed to change the CPU frequency to 18.5 MHz > (I might have a bug lurking there) and PERIPHCLK is 1/2 of that, > i.e 9.25 MHz. So at least we are on the right path. But it looks to me that this call is not getting propagated well. >From the attachment you gave initially, the event handler for twd-timers is: tick_handle_periodic(). i.e. you are running in periodic mode and not onshot... why ? > Yes, I do, but I was trying to use as much generic code as > possible to limit the chances of introducing bugs. Hmm.. > I'll take a fresh look at the ARM GLOBAL TIMER, but last I > checked, it didn't seem to handle frequency scaling. why is that required? Why will you change its freq ? The same timer is probably used for SPEAr (the platform I used to work on): http://lxr.free-electrons.com/source/arch/arm/mach-spear/time.c?v=3.14