On 13 July 2017 at 12:13, Jisheng Zhang <jszhang@xxxxxxxxxxx> wrote: > On Thu, 13 Jul 2017 11:52:54 +0200 Ulf Hansson wrote: > >> On 13 July 2017 at 11:25, Jisheng Zhang <jszhang@xxxxxxxxxxx> wrote: >> > Hi Ulf, >> > >> > On Thu, 13 Jul 2017 11:18:32 +0200 Ulf Hansson wrote: >> > >> >> On 13 July 2017 at 00:16, Zhoujie Wu <zjwu@xxxxxxxxxxx> wrote: >> >> > From: Hu Ziji <huziji@xxxxxxxxxxx> >> >> > >> >> > Add Xenon specific system-level suspend and resume support. >> >> > Especially during resume, re-configure Xenon specific registers >> >> > since registers setting will be lost in suspend if Xenon is power off. >> >> >> >> I recommend to start with deploying runtime PM support instead of >> >> system PM support. Then on top of such change, you should make use of >> >> the runtime PM centric path to get system sleep support for "free" >> >> (and thus all the nice benefits). >> > >> > I'm not sure whether runtime PM is useful for xenon case. The xenon HW >> > support ACG(Auto Clock Gating) and SDCLK-Off-While-Idle features, that's >> > to say we even don't need to do anything but achieve the runtime PM gains. >> >> Yeah, but that's only internally managed by mmc controller. The clock >> will not be unprepared/disabled, from clock tree point of view. Isn't >> that also worth doing? >> > > The HW is clock gated, the difference is clock itself. From power saving > point of view, the gain is nearly zero. From latency point of view, could I assume the clock you are talking about is the "core" clock? I then assumes that clock is used as the interface clock for the card? That makes me wonder, don't you have other device clocks to manage as well? Clocks that is provided to the controller to make it functional? > runtime PM introduce extra latency? I.E the time spent on > sdhci_runtime_suspend_host and sdhci_runtime_resume_host. There may be some latency, but exactly how much I don't know - and perhaps you could do some optimizations in that path. Moreover, you can make use of the runtime PM autosuspend feature, which I guess you know the benefits of. Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
