On Friday, November 22, 2013 12:39:24 PM Stephen Warren wrote: > On 11/22/2013 05:52 AM, Viresh Kumar wrote: > > On 22 November 2013 18:07, Rafael J. Wysocki <r...@rjwysocki.net> wrote: > >> On Friday, November 22, 2013 04:59:49 PM Viresh Kumar wrote: > >>> Some platforms might want to change frequency before suspending > >>> governors. Like: > >>> - Some platform which want to set freq to max to speed up > >>> suspend/hibernation > >>> process. > >>> - Some platform (like: Tegra or exynos), set this to min or bootloader's > >>> frequency. > >>> > >>> This patch adds an option for those, so that they can specify this at > >>> call to > >>> ->init(), so that cpufreq core can take care of this before suspending > >>> system. > >>> > >>> If this variable is not updated by ->init() then its value would be zero > >>> and so > >>> core wouldn't do anything. > >>> > >>> Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org> > >> > >> I don't think this is generally necessary, because the suspend/resume > >> routines > >> added by patch [1/2] will be executed very late during suspend or very > >> early > >> during resume and it shouldn't really matter what performance levels the > >> CPUs > >> are at then. > > > > There are few things here: > > - I feel that the current place from where we have suspended stuff is not > > gonna > > fly. We are doing that in noirq and probably devices which might be required > > during frequency transitions might already be down.. So we *may* need to > > move that in dpm_suspend().. > > - Secondly I want to understand why Tegra/Exynos has such code which I > > mentioned above.. > > > > @Stephen, Kukjin and other samsung folks: Please provide some input here, > > before your systems break in mainline :) > > I believe we set the clock to a low value because fast clocks consume > more power. Tegra architecturally supports a number of different suspend > levels. Only some of those actually power off or gate the clock source > itself.
Hmm. Viresh, maybe make it possible for the cpufreq driver to provide suspend/resume callbacks to be executed by cpufreq_suspend() and cpufreq_resume() introduced by [1/2]? Then Tegra could set the frequencies to what it wants from there before the governors are stopped. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
