On Thu, 24 Jan 2019 17:16:37 +0100 Emil Lenngren emil.lenngren@gmail.com wrote:
Hi,
Den tors 24 jan. 2019 kl 16:28 skrev Stefan Roese sr@denx.de:
On 24.01.19 15:20, Boris Brezillon wrote:
Looks like PROGRAM LOAD (AKA write cache) does not necessarily reset the cache content to 0xFF (depends on vendor implementation), so we must fill the page cache entirely even if we only want to program the data portion of the page, otherwise we might corrupt the BBM or user data previously programmed in OOB area.
Fixes: 7529df465248 ("mtd: nand: Add core infrastructure to support SPI NANDs") Reported-by: Stefan Roese sr@denx.de Cc: stable@vger.kernel.org Signed-off-by: Boris Brezillon bbrezillon@kernel.org
Works fine (limited testing only yet), so:
Tested-by: Stefan Roese sr@denx.de Reviewed-by: Stefan Roese sr@denx.de
Thanks, Stefan
Can this quirk be made vendor specific?
We can make it vendor specific, as long as it's an opt-in thing. This way, the default behavior is the safest one, and only when we know a chip does reset the cache content on a PROGRAM LOAD time can we add this flag.
It seems a waste of SPI transfer cycles to write 0xff to the whole OOB area when we only want to program the data area if the chip doesn't need this quirk. For which logic is this needed anyway? According to the GigaDevice datasheet, if a Program Load is followed by Program Execute, "uninitialized" bytes will be set to 0xff, which is the flow that is used by spinand core.
Except you're not guaranteed that the controller can fill the page in a single spi_mem_exec_op() call (because of FIFO size limitations), so you might have one PROGRAM LOAD followed by several PROGRAM RANDOM LOAD. I guess most manufacturers reset the cache content at PROGRAM LOAD time, but GigaDevice does not.
/Emil