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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