On Thu, 2015-09-17 at 17:13 +0100, Sudeep Holla wrote: > > On 17/09/15 15:56, Yingjoe Chen wrote: > > On Thu, 2015-09-17 at 14:51 +0100, Sudeep Holla wrote: > >> > >> On 16/09/15 03:04, Yingjoe Chen wrote: > >>> From: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> > >>> > >>> Add device node to enable GPT timer. This timer will be > >>> used as sched clock source. > >>> > >> > >> Interesting any known issues with or advantage over the arch timers > >> to prefer it as sched clock source. I see even arch timers are present > >> in DT, hence the question. Or is it just a incorrect commit log ? > >> > >> How does this get selected as sched clock source ? I don't see > >> sched_clock_register in mtk_timer.c > >> > >> To be clear, I am not against adding this timer support, but just want > >> to know is it preferred for sched clock source ? if yes why ? better > >> resolution ? > > > > Hi Sudeep, > > > > Thanks for your review. > > > > I hit the send too soon and missed cover letter, please see: > > http://lists.infradead.org/pipermail/linux-mediatek/2015-September/002303.html > > > > OK > > > The main reason to use GPT as sched clock is it won't stop during idle. > > > > > > I think your are confusing the system counter with arch timers. System > counter is always-on, but the arch timers(logic implementing timers > comparators) might not be off when the processor is powered down. > > I think you need this timer and are using it for low power idle states > in which case you will use this as a clock event and not clock source. > It will be used as a hardware broadcast event source. > > There's no call to sched_clock_register in mtk_timer.c, so it can't be > the sched clock, so you need to fix the commit log. Hi Sudeep, Sorry for late reply. For sched_clock_register, please see http://lists.infradead.org/pipermail/linux-mediatek/2015-July/001547.html which was accepted in https://git.linaro.org/people/daniel.lezcano/linux.git/shortlog/refs/heads/clockevents/4.4 You are right it is also used as clock event. I think we don't need to mention those detail in commit message, so I'll change to just: "Add device node to enable GPT timer." > > [...] > > >>> diff --git a/arch/arm64/boot/dts/mediatek/mt8173.dtsi b/arch/arm64/boot/dts/mediatek/mt8173.dtsi > >>> index d18ee42..d763803 100644 > >>> --- a/arch/arm64/boot/dts/mediatek/mt8173.dtsi > >>> +++ b/arch/arm64/boot/dts/mediatek/mt8173.dtsi > >>> @@ -238,6 +238,15 @@ > >>> reg = <0 0x10007000 0 0x100>; > >>> }; > >>> > >>> + timer: timer@10008000 { > >>> + compatible = "mediatek,mt8173-timer", > >> > >> Missing documentation ? I am referring upstream and it might be in some > >> patches already queued perhaps ? > > > > This is documented in > > Documentation/devicetree/bindings/timer/mediatek,mtk-timer.txt. > > Do you mean I should add "mediatek,mt8173-timer" to that file? > > > > Yes Will do in next round. Thanks Joe.C -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
