linux-kernel - Re: [PATCH 09/27] mmc: mvsdio: Remove redundant suspend and resume callbacks

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Date:	Fri, 27 Sep 2013 10:55:47 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Chris Ball <cjb@...top.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH 09/27] mmc: mvsdio: Remove redundant suspend and resume callbacks

On 26 September 2013 17:40, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> On Thu, 26 Sep 2013, Ulf Hansson wrote:
>
>> Suspend and resume of cards are handled by the protocol layer and
>> consequently the mmc_suspend|resume_host APIs are marked as deprecated.
>
> Having the protocol layer take care of card suspend is perfectly sound.
>
> However, what about host controllers?  Shouldn't they suspend themselves
> as well?  There is certainly potential for power saving by gating clocks
> to the host IP block or the like.
>

Hi Nicolas,

You are right, host drivers shall be responsible to handle power
saving operations, like clocks, power domains, pinctrls, etc. In many
cases I think using only runtime PM should satisfy a host driver's
need to perform the proper power saving.

For mvsdio, there were no host power save operations done in the
suspend/resume callbacks, which is why I removed the callbacks
entirely.

Kind regards
Ulf Hansson

>
> Nicolas
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