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From: Marek Vasut on 2 Jun 2010 20:10
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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From: Eric Miao on 2 Jun 2010 22:40
On Thu, Jun 3, 2010 at 8:01 AM, Marek Vasut <marek.vasut(a)gmail.com> wrote:
> 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.
>

If there is a FIFO attached, may need the FIFO status when the error happens.
And a dump of the DMA registers would also be helpful.
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