2012/12/13 Ulf Hansson <ulf.hansson@xxxxxxxxxx>: > On 13 December 2012 02:51, Kevin Liu <keyuan.liu@xxxxxxxxx> wrote: >>> -----Original Message----- >>> From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc-owner@xxxxxxxxxxxxxxx] On Behalf Of Linus Walleij >>> Sent: Thursday, December 13, 2012 2:54 AM >>> To: Ulf Hansson >>> Cc: Russell King - ARM Linux; Ulf Hansson; linux-mmc@xxxxxxxxxxxxxxx; Chris Ball; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >>> Subject: Re: [PATCH] mmc: mmci: Gate the clock in runtime suspend to save power >>> >>> On Wed, Dec 12, 2012 at 12:02 PM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: >>>> On 12 December 2012 07:53, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: >>> >>>>> 1) Turn on MMC_CLKGATE for this driver (select from Kconfig) >>>>> which means that the ios will be called with f=0 whenever >>>>> the card is unused, taking into account the required number >>>>> of clocks to the card. >>>> >>>> I think MMC_CLKGATE was a good initiative in the past. But that was >>>> before runtime pm was there to use. Runtime pm suits much better for >>>> handling clock gating and other runtime power save actions that could >>>> be possible for a host driver to do. >>>> >>>> I would even suggest the MMC_CLKGATE should be removed from the >>>> protocol layer, once we see that all host drivers that used it has >>>> switch to runtime pm. >>> >>> Ah now I remember that you've actually even explained this to me ... >>> memory is too short sometimes. But I follow this idea. >>> >>> Then we have only the coordination between runtime suspend >>> and suspend proper to iron out. >>> >>> Russell's concern is valid if suspend() will not wait for runtime_suspend() >>> to complete the last cycle before suspending. > > A valid point, thanks for pointing this out clearly Linus! > > Anyway, this need to be thought of as future step, since this patch is > not changing anything to that sequence as Kevin also is pointing out. > > So, the next step is to figure how we can properly do similar actions > as in the runtime_suspend callback but as part of the suspend sequence > instead and at the same time cope with 8 clock cycles. I will push a > patch for this later, so then we can discuss more about that. > >>> >> >> pm_runtime_get_noresume is called before suspend and there are >> sdhci_runtime_pm_get/sdhci_runtime_pm_put within sdhci suspend/resume >> function. So the actual runtime_suspend won't be called after suspend >> finished. So it's same as original code without pm_runtime during >> suspend/resume. >> >>> Hm this sounds scaringly familiar to what we've discussed with >>> Kevin Hilman et al recently... >>> > > May I have your Acks on this patch? > Sure, my pleasure. Acked-by: Kevin Liu <kliu5@xxxxxxxxxxx> > Kind regards > Ulf Hansson -- 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
