From: Pratyush Yadav <p.yadav@ti.com>
To: Michael Walle <michael@walle.cc>
Cc: <linux-kernel@vger.kernel.org>, <linux-mtd@lists.infradead.org>,
Tudor Ambarus <tudor.ambarus@microchip.com>,
Miquel Raynal <miquel.raynal@bootlin.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>
Subject: Re: [RFC PATCH 2/3] mtd: spi-nor: sfdp: fix spi_nor_read_sfdp()
Date: Tue, 16 Mar 2021 16:34:02 +0530 [thread overview]
Message-ID: <20210316110400.kepjn6b654lhq4dy@ti.com> (raw)
In-Reply-To: <20210312190548.6954-3-michael@walle.cc>
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.
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.
>
> ret = spi_nor_read_raw(nor, addr, len, buf);
>
> nor->read_opcode = read_opcode;
> + nor->read_proto = read_proto;
> + nor->dirmap.rdesc = rdesc;
> nor->addr_width = addr_width;
> nor->read_dummy = read_dummy;
>
> --
> 2.20.1
>
--
Regards,
Pratyush Yadav
Texas Instruments Inc.
next prev parent reply other threads:[~2021-03-16 11:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 19:05 [RFC PATCH 1/3] mtd: spi-nor: support dumping sfdp tables Michael Walle
2021-03-12 19:05 ` [RFC PATCH 1/3] mtd: spi-nor: sfdp: remember sfdp_size Michael Walle
2021-03-16 10:42 ` Pratyush Yadav
2021-03-16 11:01 ` Michael Walle
2021-03-16 11:06 ` Pratyush Yadav
2021-03-16 11:22 ` Michael Walle
2021-03-12 19:05 ` [RFC PATCH 2/3] mtd: spi-nor: sfdp: fix spi_nor_read_sfdp() Michael Walle
2021-03-16 11:04 ` Pratyush Yadav [this message]
2021-03-16 11:15 ` Michael Walle
2021-03-16 13:15 ` Pratyush Yadav
2021-03-12 19:05 ` [RFC PATCH 3/3] mtd: spi-nor: add sysfs and SFDP support Michael Walle
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