Weird 5200/mtd-ram problem

[Wolfgang Denk]

Dear Albrecht =?iso-8859-1?b?RHJl3w==?=,

In message <1243273283.3328.0 at antares> you wrote:
>
> Thanks for youre help, and sorry for the late reply - I've been on  
> vacation...

Hally you...

> For the mtd driver, I tracked down the problem via mapram_write() (in  
> drivers/mtd/chips/map_ram.c) down to the call of map_copy_to() which is  
> actually inline_map_copy_to(), which in turn calls memcpy_toio().  I  
> *think* this is _memcpy_toio() in arch/powerpc/kernel/io.c, which  
> copies all data in long (4-byte) moves, except for the last 4 bytes.  I  
> guess I have to write my own copy function which respects the fact that  
> byte writes actually must be a read word - modify - write word  
> sequence, right?

I remember some nasty problems with memcpy*(),  especially  with  un-
aligned  accesses  over the LocalPlus Bus. I'm not sure if fixes ever
made it into 2.6; the only commit that might be related is 6989f5122f
"fec: do not use memcpy on physical addresses", but this doesn't  got
into details about the casue.

Please see here for an old (2.4.25) patch for this problem - maybe
it's worth a try on your system:

http://git.denx.de/?p=linuxppc_2_4_devel.git;a=commit;h=222bd702a59efb22bf66937f6ac844ed7327fd1a

Best regards,

Wolfgang Denk

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