On 01/21/11 17:22, Elie De Brauwer wrote:
Hello list,
I have a P2020 processor on a custom board which uses the embedded
fsl-esdhc controller. Hardware-wise this is functional and in u-boot
everything seems to behave (mmc part 0 gives the correct partition table
and ext2ls/fatls are capable of reading the contents of the sd card).
However as soon as I start Linux (2.6.36), I get all sorts of unwanted
behavior. Linux is unable to detect the partition layout (but if I do a
hexdump of the MBR, I see the endianness is swapped (last 4 bytes are aa
55 00 00). Also when I try to obtain the card registers they show the
same behavior:
# cat ./devices/soc.0/ff72e000.sdhci/mmc_host/mmc0/mmc0:0001/scr
0000b50200000000
While for comparison the same value on my (x86) laptop gives:
edb@lapedb:/sys/devices/pci0000:00/0000:00:1e.0/0000:15:00.2/mmc_host/mmc0/mmc0:0001$
cat scr
02b5000000000000
In my config I have the following set:
CONFIG_MMC_SDHCI=y
CONFIG_MMC_SDHCI_IO_ACCESSORS=y
CONFIG_MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER=y
# CONFIG_MMC_SDHCI_PCI is not set
CONFIG_MMC_SDHCI_OF=y
CONFIG_MMC_SDHCI_OF_ESDHC=y
In the meantime I've 'downgraded' this issue away. Just to share my
conclusions with the world (and perhaps somebody has an aha-erlebnis
when reading this which can identify the root cause). I did some
triaging today and found out the issue was present in 2.6.36 and
2.6.36.4 but it was not present in 2.6.35.9.
The CONFIG_MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER is not involved
because this relates to the way the registers on the SoC are accessed,
these registers are accessed in the correct way. The problem only occurs
when accessing data from the SD card (e.g. the SCR which is a card
register, but also the MBR).
--
Elie De Brauwer
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