2008-11-26 (수), 10:58 +0100, Wolfgang Denk 쓰시길: > Dear "Choe, Hyun-ho", > > In message <[EMAIL PROTECTED]> you wrote: > > I did several tests for my b'd that has CFI Nor erase/write problem. > > > > My main problem is that flash_toggle() function doesn't work properly, > > it always returns 0 even while bus writing operation is proceeding. > > I mean, toggle bit doesn't toggle for each read operation. (refer to > > drivers/mtd/cfi_flash.c) > > Similar problems have been reported before - please see for example > http://lists.denx.de/pipermail/u-boot/2008-October/042036.html >
At first, I also suspected about atomic reading issue. But, IMHO, this is not the cause of the problem. Please refer to http://lists.denx.de/pipermail/u-boot/2008-November/043741.html ldrb/ldrh/ldr is load byte/half-word/word from memory operation in ARM. I think these operation should be atomic, in all cases. > > I found two workarounds. > > > > First, small waiting between each read. So, following code doesn't work. > > > > <SNIP> > > retval = flash_read16(addr) != flash_read16(addr); > > <SNIP> > > Eventually you are not performing atomic 16 bit read operations. > > > But, following code does work. > > > > <SNIP> > > u16 d = flash_read16(addr); > > udelay(1); > > u16 t = flash_read16(addr); > > retval = d != t; > > Hm... a plain delay would probably not change this behaviour unless > you have another problem. > I agree with you. Just a simple delay should not solve this problem. That is another reason that I think atomic read is not the cause of it. My second workaround is strange, too. In ARM code, mapping physical address to logical is actually does nothing, except re-calculating pointer with sector no. and offset. It just eating several processor cycles. > > I don't know exactly that this is caused by specific bus access > > mechanism, or simply chip silicon bug. > > I think the problem is that for some reason flash_read16() might not > result in 16bit bus accesses. Do you have a chance to verify this > suspicion, for example with a logic analyzer? > Currently, not available. Maybe digital scope is possible after a couple of days, but it may be impossible to check this kind of problem with it. > Best regards, > > Wolfgang Denk > _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
