On 06/12/18 9:49 PM, Simon Goldschmidt wrote: > Am 06.12.2018 um 16:59 schrieb Tom Rini: >> On Thu, Dec 06, 2018 at 04:23:00PM +0100, Miquel Raynal wrote: >>> Hi Wolfgang, >>> >>> Wolfgang Denk <[email protected]> wrote on Thu, 06 Dec 2018 10:32:14 +0100: >>> [...] >>>>>> Please understand that there is a fundamental difference between >>>>>> parallel NOR flash and things like NAND, SPI NOR etc. - the latter >>>>>> are storage devices, which are usually handled as block device or >>>>>> similar, i. e. you always need a driver to read data. Parallel NOR >>>>>> is not storage, it is _memory_, which is directly mapped int o >>>>>> memory. You can execute code from it. >>>>> >>>>> That's only partially true. Yes, you can read from a parallel NORs >>>>> like >>>>> if it was memory because memory controllers embedded in SoCs provide >>>>> your a direct mmio mapping. That's not true for write accesses, >>>> >>>> Right, but especially in the SPL read access is sufficient. >>> >>> 100% agreed, the SPL just needs read access. But we are talking about >>> U-Boot itself here. >> >> So, new but related question. Are we dropping the write path in the >> case of SPL? The only case I can think of where SPL might be doing an >> MTD write would be bootcount stored in env, so we should be able to drop >> those paths in the normal case. > > Based on my tests with Vignesh's series to port SF to MTD, I don't think > we drop the write part in SPL. I also brought that up in that thread. > > However, my (preliminary) test results of his work showed that SPL size > is actually reduced when using his new 'spi-nor-tiny' code. And that's > without trying to reduce MTD code size. >
To add, 'spi-nor-tiny' has only read path (write/erase returns -ENOTSUPP). There is an option to either use full stack(read+write+erase support) in SPL or use spi-nor-tiny. Boards with SPL size constraints can use spi-nor-tiny to reduces overall code size. -- Regards Vignesh _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
