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Message-ID: <cdd6bc25-6282-4e43-9909-16ab918ed983@linaro.org>
Date: Thu, 6 Jun 2024 14:33:16 +0100
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Subject: Re: [PATCH v2 2/2] mtd: spi-nor: macronix: enable quad/dual speed for
 mx25l3205d chips
To: Esben Haabendal <esben@geanix.com>, Pratyush Yadav <pratyush@kernel.org>,
 Michael Walle <mwalle@kernel.org>, Miquel Raynal
 <miquel.raynal@bootlin.com>, Richard Weinberger <richard@nod.at>,
 Vignesh Raghavendra <vigneshr@ti.com>
Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
 Rasmus Villemoes <rasmus.villemoes@prevas.dk>
References: <20240603-macronix-mx25l3205d-fixups-v2-0-ff98da26835c@geanix.com>
 <20240603-macronix-mx25l3205d-fixups-v2-2-ff98da26835c@geanix.com>
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From: Tudor Ambarus <tudor.ambarus@linaro.org>
In-Reply-To: <20240603-macronix-mx25l3205d-fixups-v2-2-ff98da26835c@geanix.com>
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On 6/3/24 14:09, 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.
> 
> 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.
> 
> Instead, we can use the SPI_NOR_TRY_SFDP flag, which forces the spi-nor
> system to try using SFDP, but fallback to the parameters specified in
> struct flash_info.
> 
> This way, boards using MX25L3205D will continue as before this change.
> That is without taking advantage of the 1-2-2 that it supports.
> 
> For MX25L3206E and MX25L3233F, the SFDP parameters are used, and they will
> therefore be using the optimal dual or quad mode supported by the flash
> and the SPI controller it is attached to.
> 
> Signed-off-by: Esben Haabendal <esben@geanix.com>
> ---
>  drivers/mtd/spi-nor/macronix.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/macronix.c b/drivers/mtd/spi-nor/macronix.c
> index ea6be95e75a5..090f28e05a5d 100644
> --- a/drivers/mtd/spi-nor/macronix.c
> +++ b/drivers/mtd/spi-nor/macronix.c
> @@ -61,7 +61,7 @@ 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_TRY_SFDP,
>  	}, {

let's remove support for MX25L3205D. You'll then be able to drop the
flash entry altogether and instead rely on SFDP to discover the flash's
capabilities.