SD card on an SPI bitbang interface (ppc4xx) not working

[Guennadi Liakhovetski <lg@denx.de>]

Hi,

I'm trying to use an SPI bitbang driver for PPC4xx [1] to talk to an 
SD-card, and it doesn't work. Enabling debugging in the mmc-spi driver I 
first saw, that the mmc layer sends MMC_GO_IDLE_STATE several times during 
initialization, after which the card enters the idle state and needs time 
to recover, however, the driver doesn't wait and keeps sending further 
commands. I am not quite sure this is bad, because queries do get answered 
(with R1_SPI_IDLE bit set), still I somehow fixed that so, that the driver 
now always repeats sending SD_APP_OP_COND until the card leaves the idle 
state, and then the driver proceeds. I know this is probably not a correct 
fix - I don't have the MMC/SD spec, I only found [2], still now I see that 
indeed the card is given a chance to initialize before any further 
commands are attempted. But then I come to the next problem: when the 
driver requests the card ID with MMC_SEND_CID I get an error back:

mmc0: starting CMD59 arg 00000001 flags 00000080
mmc_spi spi0.51:   mmc_spi: CMD59, resp R1
mmc_spi spi0.51: spi_ppc4xx_setup: mode 0, 8 bpw, 400000 hz
mmc0: req done (CMD59): 0: 00000000 00000000 00000000 00000000
mmc_sd_init_card[376]
mmc0: starting CMD10 arg 00000000 flags 000000b5
mmc0:     blksz 16 blocks 1 flags 00000200 tsac 0 ms nsac 0
mmc_spi spi0.51:   mmc_spi: CMD10, resp R1
mmc_spi spi0.51:     mmc_spi: read block, 16 bytes
mmc_spi spi0.51: read error ffffff92 (-110)
mmc_spi spi0.51: read status -110
mmc_spi spi0.51: spi_ppc4xx_setup: mode 0, 8 bpw, 400000 hz
mmc0: req done (CMD10): 0: 00000000 00000000 00000000 00000000
mmc0:     0 bytes transferred: -110
mmc_send_cxd_data[259] data err -110, cmd err 0

Any idea? Unfortunately, I do not have another platform where I could 
verify spi-mmc. Maybe someone could send me a debug log of an SD-card 
initialization in such a host? David?

Thanks
Guennadi

[1] http://article.gmane.org/gmane.linux.kernel.mentors/638 (an earlier version)
[2] http://elm-chan.org/docs/mmc/mmc_e.html
---
Guennadi Liakhovetski, Ph.D.

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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