linux-kernel - RE: [PATCH v1 3/3]mmc: changes to enable runtime PM of mmc core layer

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Date:	Tue, 30 Nov 2010 18:36:50 +0800
From:	"Gao, Yunpeng" <yunpeng.gao@...el.com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
CC:	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v1 3/3]mmc: changes to enable runtime PM of mmc core
 layer

>You shouldn't do this here.
>
>You didn't comment about or mentioned this change, but I guess you did
>it because you (quite reasonably) didn't want the card to be powered
>off as soon as mmc_blk_issue_rq() completes, and instead, you
>preferred to wait until some period of inactivity time passes.
>
>But that's not true for all mmc buses: e.g., when an SDIO function
>driver decides it's time to power off the card (e.g. user disables the
>wlan interface), there is no reason to have this delay.
>
>In addition, putting an inherent delay here will completely prevent
>anyone from achieving a synchronous idle notification on an mmc card
>(so even pm_runtime_put_sync() will now set a timer to submit a
>suspend request instead of carrying out a synchronous suspend).
>
>It looks like you can drop this change, and instead just use the
>autosuspend API from the mmc block driver (mainly use
>pm_runtime_put_autosuspend() instead of pm_runtime_put()).
>
>Another nice benefit of autosuspend is that now user space will be
>able to tweak the amount of delay by using
>/sys/devices/.../power/autosuspend_delay_ms attribute.

Thanks a lot for the nice review and comments. They're very valuable to me. I'll read it carefully and resubmit these patches later.
Thank you again :-)

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