linux-kernel - [URGENT] Re: bit errors on spitz + voipac

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Date:	Thu, 3 Jun 2010 02:01:13 +0200
From:	Marek Vasut <marek.vasut@...il.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Cyril Hrubis <metan@....cz>, Stanislav Brabec <utx@...guin.cz>,
	Eric Miao <eric.y.miao@...il.com>, dbaryshkov@...il.com,
	arminlitzel@....de, kernel list <linux-kernel@...r.kernel.org>,
	Dirk@...er-online.de, lenz@...wisc.edu, rpurdie@...ys.net,
	omegamoon@...il.com, Pavel Machek <pavel@....cz>,
	thommycheck@...il.com, zaurus-devel@...ts.linuxtogo.org,
	Haojian Zhuang <haojian.zhuang@...il.com>
Subject: [URGENT] Re: bit errors on spitz + voipac

Dne Po 8. března 2010 13:16:35 Cyril Hrubis napsal(a):
> Hi!
> 
> > - And I see display noise while CF Wi-Fi card is active.
> 
> Forgotten about this one. See for yourself, notice short black vertical
> lines flashing randomly.
> 
> http://atrey.karlin.mff.cuni.cz/~metan/outgoing/zaurus_sickness.mpg

This is not only case of spitz. I've seen LCD image falling apart on pxafb on 
Voipac PXA270 board. The image was like "torn in half and part of it was moved 
to right, the hole between staying white".

This happened exactly when I started doing a DMA transfer from a harddrive 
attached through pata_pxa. It's perfectly replicable. If I disabled DMA and let 
it run only in PIO, the image was fine.

I assume the corruption Pavel was seeing is related. My guess is the problems 
are caused when DMA between the CPU and a companion chip happens. I dunno if the 
DMA controller doesn't have enough power to supply LCD and the companion chip 
with data, but that's one of my guesses.

btw. Adjusting the DMA descriptor length in pata_pxa didn't help.

Guys, we need to investigate this as it seems to cause problems on many places.

Cheers!
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