Hi Gary & Wolfram:Thanks for youre help, and sorry for the late reply - I've been on vacation...
Am 20.05.09 21:59 schrieb(en) Gary Thomas:
Try to access this without using the cache.
Unfortunately, this is not cache related - I switched the dcache off completely - same results.
Am 20.05.09 22:01 schrieb(en) Wolfram Sang:
Does it work with byte, word and long accesses?
A word or long copy of 0x0055aaff with U-Boot works fine, but a byte copy filled the whole ram with 0x0000aaaa. The reason is apparently that the chip is attached to the local bus in 16-bit mode, which is incompatible with byte accesses. However, the Local Bus doesn't provide "low byte" or "high byte" indicators in non-muxed mode. How is this supposed to work then?
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?
Thanks, Albrecht.
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