In message 9CAC8A3B-89FA-44C3-B554-A53C79A0003D@kernel.crashing.org you wrote:
I'm told that higher frequencies we have issues using the toggle method on 85xx/86xx parts from freescale. But use DQ7 at those freq
Given the fact that the CFI code has absolutely no knowledge about which processor it is running on, this means one or both of two things:
1) There are issues with certain versions of certain toolchains which happen to be used with the processors in question
2) The processors in question are more likely to have problems with unexpected out-of-order scheduling / instruction reordering etc.
Please note that the current CFI driver accesses the flash by plain pointer references, in some cases even without using "volatile". This is supposed to cause problems sooner or later.
I think the CFI driver needs some basic rework to get ridof such pointer accesses and use proper accessor functions/macros instead to make sure we have all the memory barriers etc. we may need.
seems to work reliable for the flash parts we have on some of the boards.
If the DQ7 method works better, we could compare the code. Check for example for missing volatiles - but even better fix the code to use correct accessors.
It looks like it just uses DQ6/toggle if I'm reading the code correctly.
Note that Linux calls a (map)->write() function to access the flash.
Best regards,
Wolfgang Denk