Messages in this thread | | | Date | Tue, 16 Mar 2021 12:15:14 +0100 | From | Michael Walle <> | Subject | Re: [RFC PATCH 2/3] mtd: spi-nor: sfdp: fix spi_nor_read_sfdp() |
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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 <michael@walle.cc> >> --- >> 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.
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.
-michael
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