On 10/26/18 03:36, Rajat Srivastava wrote: <snip>
> Spansion flashes (on our boards) support both 3-byte and 4-byte addressing > modes which needs active switching. What could be added to your patch is > already supported in SFDP method. SFDP also provides information about page > size, flash density, read/write/erase commands, etc, in addition to getting > information about address width supported by flash. > >> >>> The flashes on our >>> boards (and also other vendor's board) will not work with Stefan's >>> patch. >>> >>> My patch can handle flashes with address widths of 3-byte, 4-byte or >>> both. It also takes a more generic path (as opposed to supporting only >>> specific flash models) by parsing SFDP standard parameters and then >>> deciding what address width is to be used. >> >> I still don't see why each and every SPI controller driver needs to be >> extended to support this SFDP parameter reading. Can't this be handled by >> some generic (read common) code part in the SPI flash infrastructure? > > The generic (read common) code part in the SPI flash infrastructure also > lands on respective SPI drivers which ultimately sends the commands to flash. > Currently every SPI driver has support for basic read command (which is > called after "generic read common code") but no driver has support for SFDP > reading, which is what needs to be added. > Also, only the drivers that want to make use of SFDP needs to extend support > for SFDP parameter reading. > > I am reiterating that this is how SFDP parsing has been implemented in Linux > as well and this is the generic way. Driver support is absolutely required > because SPI framework cannot directly send any command to any flash. > It sounds like your difference is how to detect 4-byte addressing should be used. Stefan's method is from the flash chip side, to check status register. The benefit is to preserve setting before U-Boot. I am not sure if it is necessary to preserve previous setting though. Rajat's method is from the controller side, to read SFDP. It can support all flash chips I presume. I guess Stefan's method will not determine Rajat's flash as 4-byte addressing because it indeed supports both 3- and 4-byte. To make Rajat's method work on Stefan's board, SFDP needs to be extended to the controller driver Stefan uses, is that right? I also guess reading SFDP is controller-specific and cannot be done in a generic way. If the new feature is useful and can be gradually extended to other controllers, it sounds good to me. My guesses could wrong though. York _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
