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

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> -----Original Message-----
> From: Tomi Valkeinen [mailto:tomi.valkeinen@xxxxxxxxx]
> Sent: Wednesday, April 21, 2010 4:40 PM
> To: Hiremath, Vaibhav
> Cc: linux-omap@xxxxxxxxxxxxxxx
> 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@xxxxxxxxxxxxxxx [mailto:linux-omap-
> > > owner@xxxxxxxxxxxxxxx] On Behalf Of Hiremath, Vaibhav
> > > Sent: Friday, April 16, 2010 4:28 PM
> > > To: Tomi Valkeinen
> > > Cc: linux-omap@xxxxxxxxxxxxxxx
> > > Subject: RE: [PATCH] OMAP: DSS2: GFX FIFO UNDERFLOW issue fixed
> > >
> > >
> > > > -----Original Message-----
> > > > From: Tomi Valkeinen [mailto:tomi.valkeinen@xxxxxxxxx]
> > > > Sent: Friday, April 16, 2010 3:08 PM
> > > > To: Hiremath, Vaibhav
> > > > Cc: linux-omap@xxxxxxxxxxxxxxx
> > > > Subject: Re: [PATCH] OMAP: DSS2: GFX FIFO UNDERFLOW issue fixed
> > > >
> > > > On Mon, 2010-03-22 at 14:09 +0100, ext hvaibhav@xxxxxx wrote:
> > > > > From: Vaibhav Hiremath <hvaibhav@xxxxxx>
> > > > >
> > > > > 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.
> 
> What kind of test apps you have?
> 
>  Tomi
> 
[Hiremath, Vaibhav] Just thought of updating you,

I had a good review of the db.c code and I don't see any issues with this, so somewhere VRFB related issue which I am missing.
The only difference between db.c and pan.c (also my applications), it doesn't write/fill the entire buffer in pan loop everytime, whereas db.c file does.

I think I need to take a look at the patch and TRM once again for this issue.

Thanks,
Vaibhav

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