Re: [PATCH] mtd: spi-nor: macronix: workaround for device id re-use

["Michael Walle" <mwalle@kernel.org>]

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Hi,

On Fri May 24, 2024 at 12:48 PM CEST, Esben Haabendal wrote:
> Macronix engineers apparantly do not understand the purpose of having
> an ID actually identify the chip and its capabilities. Sigh.
>
> The original Macronix SPI NOR flash that identifies itself as 0xC22016
> with RDID was MX25L3205D. This chip does not support SFDP, but does
> support the 2READ command (1-2-2).
>
> When Macronix announced EoL for MX25L3205D, the recommended
> replacement part was MX25L3206E, which conveniently also identifies
> itself as 0xC22016. It does not support 2READ, but supports DREAD
> (1-1-2) instead, and supports SFDP for discovering this.
>
> When Macronix announced EoL for MX25L3206E, the recommended
> replacement part was MX25L3233F, which also identifies itself as
> 0xC22016. It supports DREAD, 2READ, and the quad modes QREAD (1-1-4)
> and 4READ (1-4-4). This also support SFDP.

Thanks for collecting all this info!

> So far, all of these chips have been handled the same way by the Linux
> driver. The SFDP information have not been read, and no dual and quad
> read modes have been enabled.
>
> The trouble begins when we want to enable the faster read modes. The
> RDID command only return the same 3 bytes for all 3 chips, so that
> doesn't really help.
>
> But we can take advantage of the fact that only the old MX25L3205D
> chip does not support SFDP, so by triggering the old initialization
> mechanism where we try to read and parse SFDP, but has a fall-back
> configuration in place, we can configure all 3 chips to their optimal
> configurations.

You are (mis)using the quad info bits to trigger an sfdp read,
correct? In that case, I'd rather see a new flag in .no_sfdp_flags
to explicitly trigger the SFDP read. Then your new flash would only
need this flag and doesn't require the shenanigans with the fixup,
right?

> With this, MX25L3205D will get the faster 2READ command enabled,
> speading up reads. This should be safe.
>
> MX25L3206E will get the faster DREAD command enabled. This should also
> be safe.
>
> MX25L3233F will get all of DREAD, 2READ, QREAD and 4READ enabled. In
> order for this to actually work, the WP#/SIO2 and HOLD#/SIO3 pins must
> be correctly wired to the SPI controller.

That should already be taken care of with the spi-{tx,rx}-bus-width.

-michael

> Signed-off-by: Esben Haabendal <esben@geanix.com>
> ---
> I only have access to boards with MX25L3233F flashes, so haven't been
> able to test the backwards compatibility. If anybody has boards with
> MX25L3205D and/or MX25L3206E, please help test this patch. Keep an eye
> for read performance regression.
>
> It is worth nothing that both MX25L3205D and MX25L3206E are
> end-of-life, and is unavailable from Macronix, so any new boards
> featuring a Macronix flash with this ID will likely be using
> MX25L3233F.
> ---
>  drivers/mtd/spi-nor/macronix.c | 60 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/spi-nor/macronix.c b/drivers/mtd/spi-nor/macronix.c
> index ea6be95e75a5..c1e64ee3baa3 100644
> --- a/drivers/mtd/spi-nor/macronix.c
> +++ b/drivers/mtd/spi-nor/macronix.c
> @@ -8,6 +8,63 @@
>  
>  #include "core.h"
>  
> +/*
> + * There is a whole sequence of chips from Macronix that uses the same device
> + * id. These are recommended as EoL replacement parts by Macronix, although they
> + * are only partly software compatible.
> + *
> + * Recommended replacement for MX25L3205D was MX25L3206E.
> + * Recommended replacement for MX25L3206E was MX25L3233F.
> + *
> + * MX25L3205D does not support RDSFDP. The other two does.
> + *
> + * MX25L3205D supports 1-2-2 (2READ) command.
> + * MX25L3206E supports 1-1-2 (DREAD) command.
> + * MX25L3233F supports 1-1-2 (DREAD), 1-2-2 (2READ), 1-1-4 (QREAD), and 1-4-4
> + * (4READ) commands.
> + *
> + * In order to trigger reading optional SFDP configuration, the
> + * SPI_NOR_DUAL_READ|SPI_NOR_QUAD_READ flags are set, seemingly enabling 1-1-2
> + * and 1-1-4 for MX25L3205D. The other chips supporting RDSFDP will have the
> + * correct read commands configured based on SFDP information.
> + *
> + * As none of the other will enable 1-1-4 and NOT 1-4-4, so we identify
> + * MX25L3205D when we see that.
> + */
> +static int
> +mx25l3205d_late_init(struct spi_nor *nor)
> +{
> +	struct spi_nor_flash_parameter *params = nor->params;
> +
> +	/*                          DREAD  2READ  QREAD  4READ
> +	 *                          1-1-2  1-2-2  1-1-4  1-4-4
> +	 * Before SFDP parse          1      0      1      0
> +	 * 3206e after SFDP parse     1      0      0      0
> +	 * 3233f after SFDP parse     1      1      1      1
> +	 * 3205d after this func      0      1      0      0
> +	 */
> +	if ((params->hwcaps.mask & SNOR_HWCAPS_READ_1_1_4) &&
> +	    !(params->hwcaps.mask & SNOR_HWCAPS_READ_1_4_4)) {
> +		/* Should be MX25L3205D */
> +		params->hwcaps.mask &= ~SNOR_HWCAPS_READ_1_1_2;
> +		spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ_1_1_2],
> +					  0, 0, 0, 0);
> +		params->hwcaps.mask &= ~SNOR_HWCAPS_READ_1_1_4;
> +		spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ_1_1_4],
> +					  0, 0, 0, 0);
> +		params->hwcaps.mask |= SNOR_HWCAPS_READ_1_2_2;
> +		spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ_1_2_2],
> +					  0, 4, SPINOR_OP_READ_1_2_2,
> +					  SNOR_PROTO_1_2_2);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct spi_nor_fixups mx25l3205d_fixups = {
> +	.late_init = mx25l3205d_late_init,
> +};
> +
>  static int
>  mx25l25635_post_bfpt_fixups(struct spi_nor *nor,
>  			    const struct sfdp_parameter_header *bfpt_header,
> @@ -61,7 +118,8 @@ static const struct flash_info macronix_nor_parts[] = {
>  		.id = SNOR_ID(0xc2, 0x20, 0x16),
>  		.name = "mx25l3205d",
>  		.size = SZ_4M,
> -		.no_sfdp_flags = SECT_4K,
> +		.no_sfdp_flags = SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ,
> +		.fixups = &mx25l3205d_fixups
>  	}, {
>  		.id = SNOR_ID(0xc2, 0x20, 0x17),
>  		.name = "mx25l6405d",
>
> ---
> base-commit: a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6
> change-id: 20240524-macronix-mx25l3205d-fixups-882e92eed7d7
>
> Best regards,


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