linux-kernel - Re: [PATCH v3 1/2] mtd: spi-nor: add support to non-uniform SFDP SPI NOR flash memories

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Message-ID: <a62a8dc2-796d-8560-22d9-9377f39cbf52@gmail.com>
Date:   Tue, 11 Sep 2018 20:55:58 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>, dwmw2@...radead.org,
        computersforpeace@...il.com, boris.brezillon@...tlin.com,
        richard@....at
Cc:     linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        cyrille.pitchen@...rochip.com, nicolas.ferre@...rochip.com,
        Cristian.Birsan@...rochip.com
Subject: Re: [PATCH v3 1/2] mtd: spi-nor: add support to non-uniform SFDP SPI
 NOR flash memories

On 09/11/2018 05:40 PM, Tudor Ambarus wrote:
> Based on Cyrille Pitchen's patch https://lkml.org/lkml/2017/3/22/935.
> 
> This patch is a transitional patch in introducing  the support of
> SFDP SPI memories with non-uniform erase sizes like Spansion s25fs512s.
> Non-uniform erase maps will be used later when initialized based on the
> SFDP data.
> 
> Introduce the memory erase map which splits the memory array into one
> or many erase regions. Each erase region supports up to 4 erase types,
> as defined by the JEDEC JESD216B (SFDP) specification.
> 
> To be backward compatible, the erase map of uniform SPI NOR flash memories
> is initialized so it contains only one erase region and this erase region
> supports only one erase command. Hence a single size is used to erase any
> sector/block of the memory.
> 
> Besides, since the algorithm used to erase sectors on non-uniform SPI NOR
> flash memories is quite expensive, when possible, the erase map is tuned
> to come back to the uniform case.
> 
> The 'erase with the best command, move forward and repeat' approach was
> suggested by Cristian Birsan in a brainstorm session, so:
> 
> Suggested-by: Cristian Birsan <cristian.birsan@...rochip.com>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>

Reviewed-by: Marek Vasut <marek.vasut@...il.com>

-- 
Best regards,
Marek Vasut