The current code works because most CPU Bus Interface Unit will execute buswide cycles and discard the unused byte(s).
I understand that you would like to convert this code to use memcpy() and pick various bytes from local ram instead of directly from flash. Right? What exactly you are experiencing when you use current code. Could you refresh my memory?
The problem we experienced here is that the flash(am29lv641d) could not get the correct size during boot up(the error message like "FLASH: ....255 erase regions found, only 4 used...0kB" is printed out), could not be read correctly by flinfo, could not erased or written etc. It is because the num_erase_regions got a wrong value by flash_read_uchar(info, FLASH_OFFSET_NUM_ERASE_REGIONS)in line 1204. It happened only after the latest update of cfi_flash driver after u-boot 1.1.6 released. This update added a flash_read_jedec_ids before reading num_erase_resions. We suspect that reset command in flash_read_jedec_ids()may cause the problem. After the last reset in this function, a flash_write_cmd() follows it, then the flash_read_uchar is executed directly after. This flash_read_uchar returns a wrong number(124, 255 for num_erase_regions etc.). If this flash_read_uchar here reads some other flash info other than FLASH_OFFSET_NUM_ERASE_REGIONS by uchar, it also returns wrong value.
I do not like memcpy() as it is a black box. It could be implemented at low level using string instructions, it could do various things for different cpu architectures and various sizes so it could lead to very hard to find issues.
I agree.
My proposal for you to try: Do not depend on bus interface unit doing buswide reads, explicitly read buswide chunks after doing the bus-wide read into a temporary variable, pick the usable bytes from that temporary variable. This should eliminate the bus interface unit dependency of the CPU and possible board designer interfacing gimmicks.
Thanks a lot. :)
Let us know how it goes (can you post your patch too so I can verify it).
Zhang Wei is on vacation this week, he had generated a new patch to implement it with the similar idea last week. He will post his new patch after he is back.
Thanks.
Haiying