Re: [PATCH 7/7] mmc_spi: support for non-byte-aligned cards

[Wolfgang Mües]

Will,

Am Mittwoch, 11. März 2009 schrieb Will Newton:
> <wolfgang.mues@xxxxxxxxxxxx> wrote:
> > From: Wolfgang Muees <wolfgang.mues@xxxxxxxxxxxx>
> >
> > o A very large subset of SD cards in the market send their
> >  responses and data non-byte-aligned. So add logic to the
> >  mmc spi driver to handle this mess.
>
> Are you sure about this?

Yes.

> Do you have any further references for this 
> or examples of cards that exhibit this problem?

Kingston. The 1 GByte SD card, and a 128 MByte microSD card. I have got some 
reports from other mmc spi users with the same problem.

The SD protocoll ist NOT byte-aligned. Messages are starting with a 
leading "0" bit. I think some chip vendors have adapted the SPI mode from SD 
mode and forgotten to do propper byte alignment. 

> Are you sure your SPI host controller is operating correctly?

Yes. My logic probe gives the same results as my spi host controller.
For some cards, you can see the bit offset is getting larger if the
controller on the SD card is getting more and more busy...

best regards
 
i. A. Wolfgang Mües
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