linux-kernel - Re: [RFC/RFT PATCH v1 9/9] mtd: spi: Skip reading the Serial Flash Discoverable Parameters

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Date:   Sat, 29 Sep 2018 22:57:16 +0200
From:   Lukasz Majewski <lukma@...x.de>
To:     Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>
Cc:     Frieder Schrempf <frieder.schrempf@...eet.de>,
        boris.brezillon@...tlin.com, Mark Rutland <mark.rutland@....com>,
        yogeshnarayan.gaur@....com, richard@....at, broonie@...nel.org,
        linux-kernel@...r.kernel.org, Stefan Agner <stefan@...er.ch>,
        linux-spi@...r.kernel.org, albert.aribaud@...ev.fr,
        prabhakar.kushwaha@....com, linux-mtd@...ts.infradead.org,
        david.wolfe@....com, Fabio Estevam <fabio.estevam@....com>,
        han.xu@....com, computersforpeace@...il.com,
        Fabio Estevam <festevam@...il.com>, dwmw2@...radead.org
Subject: Re: [RFC/RFT PATCH v1 9/9] mtd: spi: Skip reading the Serial Flash
 Discoverable Parameters

Hi Cyrille,

> Hi Lukasz,
> 
> Le 27/09/2018 à 00:07, Lukasz Majewski a écrit :
> > The fsl-quadspi.c driver is not supporting SPINOR_OP_RDSFDP (0x5a)
> > read opcode - in the legacy driver we do read some garbage
> > data from AHB mapped area and then return on the first check  
> 
> If your controller reads garbage then spi_nor_parse_sfdp() fails and
> exists on the very first check: signature of the SFDP header. Hence
> everything should already go on as if the SPI_NOR_SKIP_SFDP flag is
> set.

Yes, this is the observed behaviour.

> 
> So this patch doesn't change anything for your controller but
> prevents other controller from using QSPI protocols like SPI 1-4-4.
> 
> This patch introduces a regression for other chips.

As stated in the patch series cover letter - this is to explicitly show
problems with qspi on vf610.

Thanks for your review.

> 
> Best regards,
> 
> Cyrille
> 
> > (L2376 @ ./mtd/spi-nor/spi-nor.c)
> > 
> > Signed-off-by: Lukasz Majewski <lukma@...x.de>
> > ---
> >  drivers/mtd/spi-nor/spi-nor.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/spi-nor/spi-nor.c
> > b/drivers/mtd/spi-nor/spi-nor.c index 442102be174e..c79b8c33aeeb
> > 100644 --- a/drivers/mtd/spi-nor/spi-nor.c
> > +++ b/drivers/mtd/spi-nor/spi-nor.c
> > @@ -1103,7 +1103,7 @@ static const struct flash_info spi_nor_ids[]
> > = { { "n25q064",     INFO(0x20ba17, 0, 64 * 1024,  128, SECT_4K |
> > SPI_NOR_QUAD_READ) }, { "n25q064a",    INFO(0x20bb17, 0, 64 *
> > 1024,  128, SECT_4K | SPI_NOR_QUAD_READ) }, { "n25q128a11",
> > INFO(0x20bb18, 0, 64 * 1024,  256, SECT_4K | SPI_NOR_QUAD_READ) },
> > -	{ "n25q128a13",  INFO(0x20ba18, 0, 64 * 1024,  256,
> > SECT_4K | SPI_NOR_QUAD_READ | SPI_NOR_DUAL_READ) },
> > +	{ "n25q128a13",  INFO(0x20ba18, 0, 64 * 1024,  256,
> > SECT_4K | SPI_NOR_QUAD_READ | SPI_NOR_DUAL_READ |
> > SPI_NOR_SKIP_SFDP) }, { "n25q256a",    INFO(0x20ba19, 0, 64 *
> > 1024,  512, SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },
> > { "n25q256ax1",  INFO(0x20bb19, 0, 64 * 1024,  512, SECT_4K |
> > SPI_NOR_QUAD_READ) }, { "n25q512a",    INFO(0x20bb20, 0, 64 * 1024,
> > 1024, SECT_4K | USE_FSR | SPI_NOR_QUAD_READ) }, 




Best regards,

Lukasz Majewski

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