Re: [PATCH] OMAP: DSS2: GFX FIFO UNDERFLOW issue fixed

["Ville Syrjälä" <ville.syrjala@nokia.com>]

On Tue, May 04, 2010 at 03:23:10PM +0200, ext Hiremath, Vaibhav wrote:
> 
> > -----Original Message-----
> > From: Tomi Valkeinen [mailto:tomi.valkeinen@nokia.com]
> > Sent: Wednesday, April 21, 2010 4:40 PM
> > To: Hiremath, Vaibhav
> > Cc: linux-omap@vger.kernel.org
> > Subject: RE: [PATCH] OMAP: DSS2: GFX FIFO UNDERFLOW issue fixed
> > 
> > On Wed, 2010-04-21 at 12:45 +0200, ext Hiremath, Vaibhav wrote:
> > > > -----Original Message-----
> > > > From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
> > > > owner@vger.kernel.org] On Behalf Of Hiremath, Vaibhav
> > > > Sent: Friday, April 16, 2010 4:28 PM
> > > > To: Tomi Valkeinen
> > > > Cc: linux-omap@vger.kernel.org
> > > > Subject: RE: [PATCH] OMAP: DSS2: GFX FIFO UNDERFLOW issue fixed
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Tomi Valkeinen [mailto:tomi.valkeinen@nokia.com]
> > > > > Sent: Friday, April 16, 2010 3:08 PM
> > > > > To: Hiremath, Vaibhav
> > > > > Cc: linux-omap@vger.kernel.org
> > > > > Subject: Re: [PATCH] OMAP: DSS2: GFX FIFO UNDERFLOW issue fixed
> > > > >
> > > > > On Mon, 2010-03-22 at 14:09 +0100, ext hvaibhav@ti.com wrote:
> > > > > > From: Vaibhav Hiremath <hvaibhav@ti.com>
> > > > > >
> > > > > > In case of 720P with 90/270 degree rotation, the system reports
> > > > > > GFX_FIFO_UNDERFLOW error which usually happens if DSS DMA is not
> > able to
> > > > > fill
> > > > > > the FIFO as per requirement.
> > > > > >
> > > > > > In TRM (section 11.2.6.1.3), where is has been clearly mentioned
> > that,
> > > > > >
> > > > > > "To improve the performance on 90 degree rotation, split the data
> > access
> > > > > on
> > > > > > write side and not read side."
> > > > > >
> > > > > > That means, read should always happen on 0 degree and write should
> > go to
> > > > > > respective rotation view.
> > > > > >
> > > > >
> > > > > With this patch my db test app (from
> > > > > git://gitorious.org/linux-omap-dss2/omapfb-tests.git) shows a lot of
> > > > > tearing when rotation != 0. I tested this on 3430SDP using the LCD.
> > > [Hiremath, Vaibhav] Tomi,
> > >
> > > Yes, just now I tried your db application and I am also seeing tearing
> > effect. All other apps (including the one which I used for testing) works
> > fine for other rotation angles.
> > >
> > > Let me debug further before commenting anything on this, I just thought of
> > updating you on this.
> > 
> > "db" app uses double buffering for updating the display, with maximum
> > update rate. There's also "pan" app, that does a bit similar thing using
> > fb offsets.
> [Hiremath, Vaibhav] Tomi,
> 
> I found the bug which is causing tearing effect, I tested it here with both, mine and your applications and for me it is working fine.
> 
> Can you please check at your end?
> (Sorry for the attachment)

You should really avoid that. I can't quote the patch.

What are those CW<->CCW swaps that you do in the patch?

Also I think the ioremap stuff is a bit broken since AFAICS it will
leave the old angle still mapped when you rotate to another angle.

-- 
Ville Syrjälä
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