On Tue, May 29, 2012 at 11:12:54AM +0200, Uwe Kleine-K?nig wrote:

Hello,

On Tue, May 29, 2012 at 10:16:09AM +0200, Sascha Hauer wrote:

quoted

The following commit changes the function used to copy from/to
the hardware buffer to memcpy_[from|to]io. This does not work
since the hardware cannot handle the byte accesses used by these
functions. Instead of reverting this patch introduce 32bit
correspondents of these functions.

Hmm, I didn't run an mtd test suite, but on mx27 it worked for me. IMHO
it's surprising that memcpy used to work, but memcpy_fromio doesn't. I
wouldn't expect a different semantic (apart from normal vs. __iomem
memory). And I wonder what will break when ARM's memcpy_fromio et al.
is optimized.

Have a look at the (ARM) implementation of memcpy_fromio:

void _memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
{
	unsigned char *t = to;
	while (count) {
		count--;
		*t = readb(from);
		t++;
		from++;
	}
}

Appearently this uses byte accesses which do not work on NFC SRAM,
whereas memcpy uses optimized (so 32bit whenever possible) accesses.
If someone would implement an optimized version of memcpy_fromio, it
would work for the NFC aswell.

btw on i.MX27 byte accesses also do not work on NFC SRAM, so I doubt
this worked for you.

Sascha

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