Hi Ulf On Tue, 1 Oct 2013, Ulf Hansson wrote: > On 30 September 2013 23:10, Guennadi Liakhovetski <g.liakhovetski@xxxxxx> wrote: > > Hi Ulf > > > > On Mon, 30 Sep 2013, Ulf Hansson wrote: > > > >> This patchset is remove all code related to MMC_CLKGATE. A significant > >> portion of code can then be removed from the core layer which would > >> simplify maintainance. > >> > >> At the moment it seems like only some MIPS platforms were using > >> MMC_CLKGATE, but at the same time the corresponding host drivers > >> were not taking advantage of the mechanism. This made me feel confident > >> in removing the feature entirely from the mmc subsystem could be done. > >> > >> Also do note that for host drivers that would like to implement clock > >> gating as a power save operation, using runtime PM is a far easier > >> way to address this. Several host drivers is already fully supporting > >> this as well. > >> > >> Ulf Hansson (2): > >> MIPS: db1235: Don't use MMC_CLKGATE > >> mmc: core: Remove MMC_CLKGATE > > > > Do I understand correctly, that you're proposing to remove the aggressive > > clock gating feature from MMC? If so, then please take into account my > > NAK. At least two SD / MMC drivers, that I'm aware of, actively used and > > developed on multiple platforms - sh_mmcif and tmio / sdhi implement MMC > > clock gating and rely on it to save power between IO. > > Guennadi, thanks for your NAK, you have understood correctly what my > intention is. :-) > > Looking into your two examples, sh_mmcif and sh_mobile_sdhci (using > tmio), I realize that they use runtime PM in an awkward way. I would > suggest to move parts of the clock gating from .set_ios to runtime PM > callbacks instead. Obviously proper calls to pm_runtime_get|put needs > to be adopted as well. pm_runtime_get|put should be used to make sure > your "runtime resources" are active while I/O operations are ongoing, > they aren't in those drivers as of today. > > So to give you some more details about why I wanted to push for a > removal of MMC_CLKGATE. You have one reason above. I want host drivers > that considers power save at request inactivity, to implement proper > runtime PM support and to do clock gating as a part of runtime PM. > There are already good references, like mmci and sdhci-* for example. > > MMC_CLKGATE is an old way of dealing with clock gating for power save, > runtime PM is better suited and has been there now for a long time > now. It is time to switch. > > I don't think mmc clock gating should be depending on a separate > kernel config as MMC_CLKGATE, which likely is the reason to why there > are no defconfig that has this option enabled. Instead RUNTIME_PM > already has this implicit meaning of handling with power save at > request inactivity. > > Finally, it is nice to remove code from a maintenance point of view. > The MMC_CLKGATE code is being used in a lot of places around the core > layer, since "mmc_host_clk_hold|release" needs to be called so many > times. > > What are your thoughts on the way forward? Could we adopt fully > runtime pm support for sh_mmcif sh_mobile_sdhci soon? Sorry, I don't have any information whether or when this will be done. Thanks Guennadi > Kind regards > Ulf Hansson > > > > > Thanks > > Guennadi > > > >> > >> Documentation/mmc/mmc-dev-attrs.txt | 10 -- > >> arch/mips/configs/db1235_defconfig | 1 - > >> drivers/mmc/core/Kconfig | 10 -- > >> drivers/mmc/core/core.c | 116 +---------------- > >> drivers/mmc/core/core.h | 3 - > >> drivers/mmc/core/debugfs.c | 5 - > >> drivers/mmc/core/host.c | 245 ----------------------------------- > >> drivers/mmc/core/mmc.c | 6 +- > >> drivers/mmc/core/sd.c | 12 +- > >> drivers/mmc/core/sdio.c | 5 +- > >> drivers/mmc/core/sdio_irq.c | 10 +- > >> include/linux/mmc/host.h | 27 ---- > >> 12 files changed, 12 insertions(+), 438 deletions(-) > >> > >> -- > >> 1.7.9.5 > >> > >> -- > >> 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 > >> > > > > --- > > Guennadi Liakhovetski, Ph.D. > > Freelance Open-Source Software Developer > > http://www.open-technology.de/ > --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- 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
