linux-kernel - Re: [PATCH v2] i2c: designware: Avoid unnecessary resuming during system suspend

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Message-ID: <20150602175532.GD1494@katana>
Date:	Wed, 3 Jun 2015 02:55:33 +0900
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Jisheng Zhang <jszhang@...vell.com>
Cc:	mika.westerberg@...ux.intel.com, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] i2c: designware: Avoid unnecessary resuming during
 system suspend

On Wed, May 20, 2015 at 10:33:13PM +0800, Jisheng Zhang wrote:
> Commit 1fc2fe204cb9 ("i2c: designware: Add runtime PM hooks") adds
> runtime pm support using the same ops for system pm and runtime pm.
> When suspend to ram, the i2c host may have been runtime suspended, thus
> i2c_dw_disable() hangs.
> 
> Previously, I fixed this issue by separating ops for system pm and
> runtime pm, then in the system suspend/resume path, runtime pm apis are
> used to ensure the device is at correct state.
> 
> But as Mika Westerberg pointed out: it sounds a bit silly to resume the
> device just because you want to call i2c_dw_disable() for it before
> suspending again. He then suggested an elegant solution which keeps the
> device runtime suspended during system suspend with the help of
> 'dev->power.direct_complete'. This patch adopted this solution, and in
> fact Mika provided the main code.
> 
> Signed-off-by: Jisheng Zhang <jszhang@...vell.com>

Fixed the 80 char thingie and applied to for-next, thanks!


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