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List:       linux-arm-kernel
Subject:    Re: AT91 SPI and OVRES error?
From:       "Tommaso Massimi" <tmassimi () gmail ! com>
Date:       2007-03-28 16:38:45
Message-ID: 9c4a6f0e0703280938x6672d3e7hdaeb30bc742a5ddc () mail ! gmail ! com
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On 3/21/07, Steven Scholz <steven.scholz@imc-berlin.de> wrote:
> Hi all,
>
> first things first:
> I am *not* using a recent kernel. And I am *not* using the SPI driver
> provided by the kernel. ;-)
>
> Now for all still reading here's my problem:
>
> I have to use a WLAN driver supplied by a third party.
> It's using the AT91 SPI running @ 20MHz using DMA.
>
> When sending(!) loads of data over SPI I get OVRES error.
>
> My questions:
> a) why do I get reciever overrun when sending?
> b) why do I get a overrun at all when using DMA?
>    shouldn't be the DMA fast enough to empty the receiver
>    register before new data arrives?
>
> Anyone seen the same? Maybe with the regular kernel driver?
>
> Thanks a million!!!
>
> --
> Steven

We had a similar trouble with AT91 and the SD card driver
we were developing:

it happened every time the driver task was switched
when the SD card receveid the data tranfer request
but the DMA was not yet enabled:
as the task was suspended,
the PDC was unable to manage the data.

Enabling DMA before send the data requested solved the issue.

Not sure this is your problem, but maybe these lines can help you
to do some other consideration.

Bye

--------------

www.develer.com

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