Stefan Roese sr@denx.de schrieb am Mo., 6. Aug. 2018, 17:23:
Hi Simon,
On 06.08.2018 17:15, Simon Goldschmidt wrote:
Stefan Roese <sr@denx.de mailto:sr@denx.de> schrieb am Mo., 6. Aug. 2018, 16:34:
Some SPI NOR chips only support 4-byte mode addressing. Here thedefault
3-byte mode does not work and leads to incorrect accesses. Settingthis
option enables the use of such SPI NOR chips, that only support this 4-byte mode.I think it would make more sense to enable 4-byte mode or 4-byte opcodes on all chips with more than 16 mbyte rather than having to select at compile time.
We need to be careful here. As setting the chip into 4-byte mode unconditionally (for bigger devices) will very likely cause boot problems with internal bootROMs expecting 3-byte mode.
I have a similar problem on socfpga where Linux 4.9 sets the chip into 4-byte mode and SPL cannot use it on warm reboot. However, the bootROM does not run on warm reboot on this platform.
I just think it would be good to solve these related problems in a more generic way.
Simon
As noted in the commit message, this is a very special case, where the SPI NOR only supports 4-byte opcodes / mode.
Another idea would be to check the 3-byte / 4-byte mode of the SPI NOR device upon SPI NOR driver loading and use the selected mode accordingly. This could be done without compile time options but it would not help in general for users with bigger SPI NOR devices that support both modes.
Thanks, Stefan