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From: Mike Rapoport <mike@compulab.co.il>
To: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: video4linux-list@redhat.com
Subject: Re: pxa_camera: DMA alignment requirement
Date: Sun, 16 Nov 2008 09:30:07 +0200	[thread overview]
Message-ID: <491FCBFF.9060208@compulab.co.il> (raw)
In-Reply-To: <87ljvktqtv.fsf@free.fr>

Robert Jarzmik wrote:
> Mike Rapoport <mike@compulab.co.il> writes:
> 
>> Robert Jarzmik wrote:
>>> Hello,
>>>
>>> In the pxa camera driver, the 3 DMA channels used are MMU page aligned. Does
>>> somebody remember where that constraint comes from ?
>>>
>> As far as I remember, the buffers should be page aligned to allow overlaying of
>> captured data.
> Ah, so that's it, thanks.
> 
>>From what I read on the PXA manual, the only constraint is 16bytes
> alignement. Would you also remember who wrote the code, so that I can ask him
> where he read about page alignement constraint please ?

Just by coincidence it was me :)
I used pxafb_overlay from [1], and my (mis)understanding of what it does added
the page alignment constrain. Now looking at the overlay code once more, I'm not
sure if it's necessary.


---
[1] http://www.rpsys.net/openzaurus/patches/archive/pxa27x_overlay-r8.patch

> Cheers.
> 
> --
> Robert
> 

-- 
Sincerely yours,
Mike.

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  reply	other threads:[~2008-11-16  7:30 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-09 17:01 pxa_camera: DMA alignment requirement Robert Jarzmik
2008-11-13 10:23 ` Mike Rapoport
2008-11-16  1:14   ` Robert Jarzmik
2008-11-16  7:30     ` Mike Rapoport [this message]
2008-11-25 21:18       ` Robert Jarzmik

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