Re: [PATCH v1] mtd: spi-nor: unset quad_enable if SFDP doesn't specify it

Tudor.Ambarus
2022-03-07T07:13:07Z

On 3/4/22 20:51, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> While the first version of JESD216 specify the opcode for 4 bit I/O
> accesses, it lacks information on how to actually enable this mode.
>
> For now, the one set in spi_nor_init_default_params() will be used.
> But this one is likely wrong for some flashes, in particular the
> Macronix MX25L12835F. Thus we need to clear the enable method when
> parsing the SFDP. Flashes with such an SFDP revision will have to use a
> flash (and SFDP revision) specific fixup.
>
> This might break quad I/O for some flashes which relied on the
> spi_nor_sr2_bit1_quad_enable() that was formerly set. If your bisect
> turns up this commit, you'll probably have to set the proper
> quad_enable method in a post_bfpt() fixup for your flash.
>

Right, I meant adding a paragraph such as the one from above.

> Signed-off-by: Michael Walle <michael@walle.cc>
> Tested-by: Heiko Thiery <heiko.thiery@gmail.com>
> ---
> changes since RFC:
> - reworded commit message
> - added comment about post_bfpt hook
>
> Tudor, I'm not sure what you meant with
> Maybe you can update the commit message and explain why would some
> flashes fail to enable quad mode, similar to what I did.
>
> It doesn't work because the wrong method is chosen? ;)
>
> drivers/mtd/spi-nor/sfdp.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
> index a5211543d30d..6bba9b601846 100644
> --- a/drivers/mtd/spi-nor/sfdp.c
> +++ b/drivers/mtd/spi-nor/sfdp.c
> @@ -549,6 +549,16 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
> map->uniform_erase_type = map->uniform_region.offset &
> SNOR_ERASE_TYPE_MASK;
>
> + /*
> + * The first JESD216 revision doesn't specify a method to enable
> + * quad mode. spi_nor_init_default_params() will set a legacy
> + * default method to enable quad mode. We have to disable it
> + * again.
> + * Flashes with this JESD216 revision need to set the quad_enable
> + * method in their post_bfpt() fixup if they want to use quad I/O.
> + */

Great. Looks good to me. I'll change the subject to "mtd: spi-nor: sfdp:"
when applying.

Cheers,
ta
> + params->quad_enable = NULL;
> +
> /* Stop here if not JESD216 rev A or later. */
> if (bfpt_header->length == BFPT_DWORD_MAX_JESD216)
> return spi_nor_post_bfpt_fixups(nor, bfpt_header, &bfpt);
> @@ -562,7 +572,6 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
> /* Quad Enable Requirements. */
> switch (bfpt.dwords[BFPT_DWORD(15)] & BFPT_DWORD15_QER_MASK) {
> case BFPT_DWORD15_QER_NONE:
> - params->quad_enable = NULL;
> break;
>
> case BFPT_DWORD15_QER_SR2_BIT1_BUGGY:
> --
> 2.30.2