[U-Boot-Users] MMC Card Problems with U-Boot 1.1.6

[Pete MacKay <linux@architechnical.net>]

Thanks for the pointers!  I replaced that with the values read from the CSD,
which was a task in itself as the 270 seemed to add a 0x3F and drop the
CRC/0x01 byte in the response (which is reversed byte-order).

You're right that the cards can be told apart with the proper init sequence
(the right way for submission), but I added 'sd' commands and interface in
the interest of time and preserving the original MMC code line.  Fortunately
adding commands to u-boot is easy!  :)  CMD1 isn't supported in SD 2.0 (it
times out), which does added negotiation (CMD8/ACMD41).  Linux very recently
added SDHC (high capacity) support and last I heard they were debating
whether the sequence should check for MMC first (CMD1) or SD (CMD8).

Alas, the kernel code is layered and complex, but is a good place to start. 
I've been looking through it for 270 caveats (there are several) and now my
brain hurts...


Haavard Skinnemoen-2 wrote:
> 
> I think I know where I'd start looking ;-)
> 
>                 /* FIXME fill in the correct size (is set to 32MByte) */
>                 mmc_dev.blksz = 512;
>                 mmc_dev.lba = 0x10000;
> 
> Btw, why do you need an sdinit command? It should be possible to tell
> the difference between SD and MMC cards automatically. In fact, I know
> it's possible because the Linux driver does it, and the at32ap7000 mmc
> driver I haven't submitted yet does it.
> 
> Haavard
> 

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