On 16/03/21 12:15PM, Michael Walle wrote: > Am 2021-03-16 12:04, schrieb Pratyush Yadav: > > On 12/03/21 08:05PM, Michael Walle wrote: > > > If spi_nor_read_sfdp() is used after probe, we have to set read_proto > > > and the read dirmap. > > > > > > Signed-off-by: Michael Walle <[email protected]> > > > --- > > > drivers/mtd/spi-nor/sfdp.c | 8 ++++++++ > > > 1 file changed, 8 insertions(+) > > > > > > diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c > > > index b1814afefc33..47634ec9b899 100644 > > > --- a/drivers/mtd/spi-nor/sfdp.c > > > +++ b/drivers/mtd/spi-nor/sfdp.c > > > @@ -179,19 +179,27 @@ static int spi_nor_read_sfdp(struct spi_nor > > > *nor, u32 addr, > > > size_t len, void *buf) > > > { > > > u8 addr_width, read_opcode, read_dummy; > > > + struct spi_mem_dirmap_desc *rdesc; > > > + enum spi_nor_protocol read_proto; > > > int ret; > > > > > > read_opcode = nor->read_opcode; > > > + read_proto = nor->read_proto; > > > + rdesc = nor->dirmap.rdesc; > > > addr_width = nor->addr_width; > > > read_dummy = nor->read_dummy; > > > > > > nor->read_opcode = SPINOR_OP_RDSFDP; > > > + nor->read_proto = SNOR_PROTO_1_1_1; > > > + nor->dirmap.rdesc = NULL; > > > nor->addr_width = 3; > > > nor->read_dummy = 8; > > > > NACK. You can't assume the device is still in 1S-1S-1S mode after probe. > > For example, the s28hs512t flash is switched to 8D-8D-8D mode by the > > time the probe finishes so this would be an invalid command. Same for > > any flash that goes into a stateful mode. > > I see. > > > And you can't even keep using nor->read_proto to read SFDP because the > > Read SFDP command might not be supported in all modes. xSPI spec > > (JESD251) says that the Read SFDP command is optional in 8D-8D-8D mode. > > > > I think the best approach for this would be to cache the entire SFDP > > table at parse time. This obviously comes with a memory overhead but I > > don't think it would be too big. For example, the sfdp table on > > s28hs512t is 491 bytes and it has 6 tables. Anyway, if the memory usage > > is too much of a problem we can put the feature behind a config. > > I don't like to have it a config option, because then, if you really > need it, i.e. some user has an unknown flash, it might not be there.
Right. Then let's hope people don't mind us using up an extra half kilobyte or so. > > The next question would be, should I leave the current parsing code > as is or should I also change that to use the sftp data cache. I'd > prefer to leave it as is. For this series its fine if you leave it as is. But eventually it would be a good idea to convert all SFDP parsers to use the cache to reduce the number of SFDP reads and potentially speed up flash initialization a bit. -- Regards, Pratyush Yadav Texas Instruments Inc.
