Re: FW: [PATCH 0/3] mmc: Use runtime pm for blkdevice

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> From: Ulf Hansson <ulf.hansson@xxxxxxxxxxxxxx<mailto:ulf.hansson@xxxxxxxxxxxxxx>>
> Date: Fri, Mar 1, 2013 at 8:47 PM
> Subject: [PATCH 0/3] mmc: Use runtime pm for blkdevice
> To: linux-mmc@xxxxxxxxxxxxxxx<mailto:linux-mmc@xxxxxxxxxxxxxxx>, Chris Ball <cjb@xxxxxxxxxx<mailto:cjb@xxxxxxxxxx>>
> Cc: Johan Rudholm <johan.rudholm@xxxxxxxxxxxxxx<mailto:johan.rudholm@xxxxxxxxxxxxxx>>, Ulf Hansson <ulf.hansson@xxxxxxxxxx<mailto:ulf.hansson@xxxxxxxxxx>>
>
>
> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx<mailto:ulf.hansson@xxxxxxxxxx>>
>
> SDIO has been using runtime pm for a while to handle runtime power save
> operations. This patchset is enabling the option to make the sd/mmc
> blockdevices to use runtime pm as well.
>
> The runtime pm implementation for the block device will make use of
> autosuspend to defer power save operation to after request inactivty for
> a certain time.
>
> To actually perform some power save operations the corresponding bus ops
> for mmc and sd shall be implemented. Typically it could make sense to do
> BKOPS for eMMC in here.
>
> Ulf Hansson (3):
>   mmc: core: Remove power_restore bus_ops for mmc and sd
>   mmc: core: Add bus_ops for runtime pm callbacks
>   mmc: block: Enable runtime pm for mmc blkdevice
>
Ulf,

sdhci.c has added pm_runtime which also protect between request and
task finish. And some sdhci.c based host drivers has provided
pm_runtime_suspend/resume functions like sdhci-pxav3.c. From the
powersave viewpoint, I think adding pm_runtime in driver level is
better than doing that on bus level since the control granularity is
even smaller. And adding pm_runtime in both block.c and sdhci.c will
call pm_runtime twice. How do you think?

Thanks
Kevin
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