fsl-esdhc on P2020 weird endianess behavior

tiejun.chen tiejun.chen at windriver.com
Mon Jan 24 19:15:14 EST 2011

Elie De Brauwer wrote:
> On 01/24/11 04:26, tiejun.chen wrote:
>> 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
>> Can you re-partition that under Linux? i.e, you can use fdisk to do
>> this. Then
>> I'm a bit curious what it'll be happened.
> This was already partitioned under (x86) Linux, and when I plug it into

I means you should partition the disk on the PPC Linux, not x86. As you know x86
work with LE for Linux, but PPC with BE. So I think you should partition that on
the same type machine. Can you try it?

> my laptop it sees the MBR (but also on target, in U-boot, the mmc part 0
> command shows the correct partition table). And this does not explain

I didn't check this implemented codes within u-boot. Maybe u-boot can do
something to swap MMC ending problem. You can try to get the conclusion. Firstly
you can re-partition that on PPC Linux then check if u-boot can identify it
properly. I guess u-boot still can read that successfully.


> why the card registers (such as the scr pasted below) also seem to have
> their endianess swapped, which will result in other side-effects, such
> as improper reading of card capabilities.
>>> 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 at 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_PCI is not set
>> At least looks the config is fine.
>> Tiejun

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