linux-kernel - Re: [PATCH v6 2/4] mtd: m25p80: add support of SPI 1-2-2 and 1-4-4 protocols

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Date:   Mon, 17 Apr 2017 00:28:40 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        linux-mtd@...ts.infradead.org, kdasu.kdev@...il.com
Cc:     computersforpeace@...il.com, dwmw2@...radead.org,
        boris.brezillon@...e-electrons.com, richard@....at,
        linux-kernel@...r.kernel.org, jartur@...ence.com,
        mar.krzeminski@...il.com
Subject: Re: [PATCH v6 2/4] mtd: m25p80: add support of SPI 1-2-2 and 1-4-4
 protocols

On 04/16/2017 11:41 PM, Cyrille Pitchen wrote:
> Before this patch, m25p80_read() supported few SPI protocols:
> - regular SPI 1-1-1
> - SPI Dual Output 1-1-2
> - SPI Quad Output 1-1-4
> On the other hand, m25p80_write() only supported SPI 1-1-1.
> 
> This patch updates both m25p80_read() and m25p80_write() functions to let
> them support SPI 1-2-2 and SPI 1-4-4 protocols for Fast Read and Page
> Program SPI commands.
> 
> It adopts a conservative approach to avoid regressions. Hence the new
> implementations try to be as close as possible to the old implementations,
> so the main differences are:
> - the tx_nbits values now being set properly for the spi_transfer
>   structures carrying the (op code + address/dummy) bytes
> - and the spi_transfer structure being split into 2 spi_transfer
>   structures when the numbers of I/O lines are different for op code and
>   for address/dummy byte transfers on the SPI bus.
> 
> Besides, the current spi-nor framework supports neither the SPI 2-2-2 nor
> the SPI 4-4-4 protocols. So, for now, we don't need to update the
> m25p80_{read|write}_reg() functions as SPI 1-1-1 is the only one possible
> protocol.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...el.com>

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

-- 
Best regards,
Marek Vasut