* SPI controller bugfixes needed (full duplex + DMA, data corruption)
@ 2008-11-15 22:22 David Brownell
[not found] ` <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
0 siblings, 1 reply; 4+ messages in thread
From: David Brownell @ 2008-11-15 22:22 UTC (permalink / raw)
To: kernel-bIcnvbaLZ9MEGnE8C9+IrQ, Andrea
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f
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.
- Dave
p.s. Note that full duplex transfers became a bit more
common after f9b90e39cbc5c4d6ef60022fd1f25d541df0aad1
merged (in the 2.6.28-rc0 merge frenzy).
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: SPI controller bugfixes needed (full duplex + DMA, data corruption)
[not found] ` <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
@ 2008-11-18 7:52 ` Sascha Hauer
[not found] ` <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
0 siblings, 1 reply; 4+ messages in thread
From: Sascha Hauer @ 2008-11-18 7:52 UTC (permalink / raw)
To: David Brownell
Cc: a.paterniani-03BXCEkGbFHYGGNLXY5/rw, AndreaPaterniani,
kernel-bIcnvbaLZ9MEGnE8C9+IrQ,
spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f
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
--
Pengutronix - Linux Solutions for Science and Industry
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: SPI controller bugfixes needed (full duplex + DMA, data corruption)
[not found] ` <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
@ 2008-11-18 8:30 ` Andrea Paterniani
[not found] ` <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>
0 siblings, 1 reply; 4+ messages in thread
From: Andrea Paterniani @ 2008-11-18 8:30 UTC (permalink / raw)
To: Sascha Hauer
Cc: David Brownell,
spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f,
kernel-bIcnvbaLZ9MEGnE8C9+IrQ
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*
*SWAPP* - Studio Professionale
Via degli Abeti, 312 - 61100 Pesaro
Tel 0721 24256
Fax 178 220 8730
a.paterniani-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org
www.swapp-eng.it
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: SPI controller bugfixes needed (full duplex + DMA, data corruption)
[not found] ` <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>
@ 2008-11-18 22:04 ` David Brownell
0 siblings, 0 replies; 4+ messages in thread
From: David Brownell @ 2008-11-18 22:04 UTC (permalink / raw)
To: Andrea Paterniani
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f,
kernel-bIcnvbaLZ9MEGnE8C9+IrQ
On Tuesday 18 November 2008, Andrea Paterniani wrote:
> 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).
Cool ... "solves old problems". ;)
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^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2008-11-18 22:04 UTC | newest]
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-- links below jump to the message on this page --
2008-11-15 22:22 SPI controller bugfixes needed (full duplex + DMA, data corruption) David Brownell
[not found] ` <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2008-11-18 7:52 ` Sascha Hauer
[not found] ` <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2008-11-18 8:30 ` Andrea Paterniani
[not found] ` <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>
2008-11-18 22:04 ` David Brownell
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