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

[Will Newton <will.newton@gmail.com>]

On Wed, Mar 11, 2009 at 2:34 PM, Wolfgang Mües
<wolfgang.mues@auerswald.de> wrote:
> Will,
>
> Am Mittwoch, 11. März 2009 schrieb Will Newton:
>> <wolfgang.mues@auerswald.de> wrote:
>> > From: Wolfgang Muees <wolfgang.mues@auerswald.de>
>> >
>> > 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.

Are they using the same host controller? Have you tried these cards
with a different host controller?

Are you clocking them particularly slow or fast?

> 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...

A logic probe may not display any signal integrity issues you might have.