Re: SPI controller bugfixes needed (full duplex + DMA, data corruption)

[Andrea Paterniani <a.paterniani-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>]

I have an iMX1 based HW running kernel 2.6.25.8.
I checked the patch and to seems to be ok (solves old problems on full 
duplex transfers).

Regards,
-- Andrea

Sascha Hauer ha scritto:
> Hi David,
>
> On Sat, Nov 15, 2008 at 02:22:32PM -0800, David Brownell wrote:
>   
>> Hi,
>>
>> We recently turned up a bug in the pxa2xx SPI driver, which
>> turns out to also be present in the spi_imx.c and au1550_spi.c
>> drivers too.
>>
>> Briefly, full duplex transfers are allowed to share the
>> same buffer (or partially overlap it), which means that
>> the dma mapping operations must be done in a safe order:
>>
>>  - first map the TX buffer, so cache data gets written
>>    to memory where the DMA will pick it up;
>>
>>  - then map the RX buffer, so that cache entries (with
>>    soon-to-be-stale data) get removed.
>>
>> Doing it the other order, as is done with spi_imx and
>> with au1550_spi, causes data corruption by discarding
>> data from the cache *before* writing it to memory.
>>
>> If you can do it, it'd be good to see this fixed before
>> the 2.6.28 kernel ships.
>>     
>
> Hm, this is a non trivial fix. I don't have a MX1 based hardware with
> something on the SPI bus handy, so this would be a shot in the dark for
> me. I hope Andrea jumps in, otherwise we'll have to wait till the driver
> works on MX2.
>
> Sascha
>
>   

-- 


 

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*Ing. Andrea Paterniani*

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