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This is a workaround for a bug in SB600 and SB700

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If we only send an opcode and no additional data/address, the SPI
controller will read one byte too few from the chip. Basically, the
last byte of the chip response is discarded and will not end up in the
FIFO. It is unclear if the CS# line is set high too early as well. That
hardware bug is undocumented as of now, but I'm working with AMD to add
a detailed description of it to the errata.

Add loads of additional debugging to SB600/SB700 init.

Add explanatory comments for unintuitive code flow.

Thanks go to Uwe for testing quite a few iterations of the patch.

Kill the SB600 flash chip status register special case, which was a
somewhat misguided workaround for that hardware erratum.

Note for future added features in the SB600 SPI driver: It may be
possible to read up to 15 bytes of command response with overlapping
reads due to the ring buffer design of the FIFO if the command can be
repeated without ill effects. Same for skipping up to 7 bytes between
command and response.

Corresponding to flashrom svn r661.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Stefan Reinauer <stepan@coresystems.de>
This commit is contained in:
Carl-Daniel Hailfinger
2009-07-23 01:36:08 +00:00
parent 414bd320ac
commit f8555e24a4
4 changed files with 53 additions and 28 deletions
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4
spi.c
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@ -367,10 +367,6 @@ uint8_t spi_read_status_register(void)
int ret;
/* Read Status Register */
if (spi_controller == SPI_CONTROLLER_SB600) { /* FIXME */
/* Workaround for SB600 hardware bug. Can be killed later. */
return sb600_read_status_register();
}
ret = spi_send_command(sizeof(cmd), sizeof(readarr), cmd, readarr);
if (ret)
fprintf(stderr, "RDSR failed!\n");