SPI trouble on Colibri 270 (PXA)...

[jakob@viketoft.se (Jakob Viketoft)]

Eric Miao wrote:
> On Wed, Apr 21, 2010 at 8:47 PM, Jakob Viketoft <jakob@viketoft.se> wrote:
>> Martin Guy wrote:
>>> On 4/21/10, Eric Miao <eric.y.miao@gmail.com> wrote:
>>>
>>>>  I thought we were talking about SPI?
>>> We are. It affects boards that have a single SD/MMC card on the SPI
>>> bus and use SFRMOUT as the chip select line, which impacts how the SPI
>>> driver needs to handle multi-part messages without dropping CS between
>>> transfers
>> Does this mean that this is a know issue with the pxa2xx spi driver? At the
>> moment I'm rather pressed for time and have instead opted for compressing
>> the two transfers (read command and actual read) into one.
> 
> I'm expecting this to be correct code, i.e. by combining read command
> transfer and actual read transfer into a single message, with .cs_change
> indicating that CS not changed during transfer. No?

The original code currently combines the two transfers in one message as
you say (leaving CS asserted unless cs_change is set). However, I don't
know if it's a problem with scheduling or that the interrupt takes too
long to serve, but on my platform the two transfers (in the same
message) doesn't go back-to-back as they should and CS gets deasserted
in the middle. Thus I have combined the two transfers into one and the
message only hold this single transfer. Now things work at my end, but
it's annoying that I don't have time to track down the real issue at the
moment...

	/Jakob