Re: [PATCH] drm: shmob_drm: Check clk_prepare_enable() return value

[Thierry Reding <thierry.reding@gmail.com>]

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On Wed, Dec 04, 2013 at 03:37:48PM +0100, Laurent Pinchart wrote:
> Hi Thierry,
> 
> On Wednesday 04 December 2013 11:01:07 Thierry Reding wrote:
> > On Wed, Dec 04, 2013 at 02:38:21AM +0100, Laurent Pinchart wrote:
> > > On Tuesday 03 December 2013 10:59:24 Thierry Reding wrote:
> > > > On Mon, Dec 02, 2013 at 01:52:20AM +0100, Laurent Pinchart wrote:
> > > > [...]
> > > > 
> > > > > diff --git a/drivers/gpu/drm/shmobile/shmob_drm_crtc.c
> > > > > b/drivers/gpu/drm/shmobile/shmob_drm_crtc.c
> > > > 
> > > > [...]
> > > > 
> > > > > @@ -170,7 +178,9 @@ static void shmob_drm_crtc_start(struct
> > > > > shmob_drm_crtc
> > > > > *scrtc)
> > > > > 
> > > > >  		return;
> > > > >  	
> > > > >  	/* Enable clocks before accessing the hardware. */
> > > > > 
> > > > > -	shmob_drm_clk_on(sdev);
> > > > > +	ret = shmob_drm_clk_on(sdev);
> > > > > +	if (ret < 0)
> > > > > +		return;
> > > > 
> > > > Perhaps this should be printing an error or using WARN_ON()? Otherwise
> > > > it might be very difficult to diagnose what's going wrong.
> > > 
> > > That's a good point. In practice, as the driver always uses a Renesas SoC
> > > MSTP clock, the clock code will print a message to the kernel log though,
> > > so I'm not sure whether we should duplicate that here. If you think we
> > > should I'll submit a new patch.
> > 
> > Is that one of the clocks implemented in drivers/sh/clk?
> 
> Correct, and in drivers/clk/shmobile/clk-mstp.c when 
> http://www.spinics.net/lists/devicetree/msg12696.html will be merged.
> 
> > There don't seem to be any error messages in the clk_enable()
> > implementation.
> 
> There will be one when http://www.spinics.net/lists/linux-sh/msg25650.html 
> will get merged :-) Before that enabling the clock never failed, with the 
> patch applied the failure is logged.

Alright,

Reviewed-by: Thierry Reding <treding@nvidia.com>

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