linux-kernel - Re: [PATCH v7 1/4] mtd: spi-nor: introduce SPI 1-2-2 and SPI 1-4-4 protocols

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Date:   Wed, 19 Apr 2017 01:02:07 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        linux-mtd@...ts.infradead.org
Cc:     computersforpeace@...il.com, dwmw2@...radead.org,
        boris.brezillon@...e-electrons.com, richard@....at,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/4] mtd: spi-nor: introduce SPI 1-2-2 and SPI 1-4-4
 protocols

On 04/19/2017 12:51 AM, Cyrille Pitchen wrote:
> This patch changes the prototype of spi_nor_scan(): its 3rd parameter
> is replaced by a 'struct spi_nor_hwcaps' pointer, which tells the spi-nor
> framework about the actual hardware capabilities supported by the SPI
> controller and its driver.
> 
> Besides, this patch also introduces a new 'struct spi_nor_flash_parameter'
> telling the spi-nor framework about the hardware capabilities supported by
> the SPI flash memory and the associated settings required to use those
> hardware caps.
> 
> Then, to improve the readability of spi_nor_scan(), the discovery of the
> memory settings and the memory initialization are now split into two
> dedicated functions.
> 
> 1 - spi_nor_init_params()
> 
> The spi_nor_init_params() function is responsible for initializing the
> 'struct spi_nor_flash_parameter'. Currently this structure is filled with
> legacy values but further patches will allow to override some parameter
> values dynamically, for instance by reading the JESD216 Serial Flash
> Discoverable Parameter (SFDP) tables from the SPI memory.
> The spi_nor_init_params() function only deals with the hardware
> capabilities of the SPI flash memory: especially it doesn't care about
> the hardware capabilities supported by the SPI controller.
> 
> 2 - spi_nor_setup()
> 
> The second function is called once the 'struct spi_nor_flash_parameter'
> has been initialized by spi_nor_init_params().
> With both 'struct spi_nor_flash_parameter' and 'struct spi_nor_hwcaps',
> the new argument of spi_nor_scan(), spi_nor_setup() computes the best
> match between hardware caps supported by both the (Q)SPI memory and
> controller hence selecting the relevant settings for (Fast) Read and Page
> Program operations.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...el.com>

[...]

> --- a/include/linux/mtd/spi-nor.h
> +++ b/include/linux/mtd/spi-nor.h
> @@ -119,13 +119,57 @@
>  /* Configuration Register bits. */
>  #define CR_QUAD_EN_SPAN		BIT(1)	/* Spansion Quad I/O */
>  
> -enum read_mode {
> -	SPI_NOR_NORMAL = 0,
> -	SPI_NOR_FAST,
> -	SPI_NOR_DUAL,
> -	SPI_NOR_QUAD,
> +/* Supported SPI protocols */
> +#define SNOR_PROTO_INST_MASK	GENMASK(23, 16)
> +#define SNOR_PROTO_INST_SHIFT	16
> +#define SNOR_PROTO_INST(_nbits)	\
> +	((((u32)(_nbits)) << SNOR_PROTO_INST_SHIFT) & SNOR_PROTO_INST_MASK)

Is the u32 cast needed ?

> +#define SNOR_PROTO_ADDR_MASK	GENMASK(15, 8)
> +#define SNOR_PROTO_ADDR_SHIFT	8
> +#define SNOR_PROTO_ADDR(_nbits)	\
> +	((((u32)(_nbits)) << SNOR_PROTO_ADDR_SHIFT) & SNOR_PROTO_ADDR_MASK)
> +
> +#define SNOR_PROTO_DATA_MASK	GENMASK(7, 0)
> +#define SNOR_PROTO_DATA_SHIFT	0
> +#define SNOR_PROTO_DATA(_nbits)	\
> +	((((u32)(_nbits)) << SNOR_PROTO_DATA_SHIFT) & SNOR_PROTO_DATA_MASK)

[...]

> +static inline u8 spi_nor_get_protocol_inst_nbits(enum spi_nor_protocol proto)
> +{
> +	return ((u32)(proto & SNOR_PROTO_INST_MASK)) >> SNOR_PROTO_INST_SHIFT;

DTTO, is the cast needed ?

> +}
> +
> +static inline u8 spi_nor_get_protocol_addr_nbits(enum spi_nor_protocol proto)
> +{
> +	return ((u32)(proto & SNOR_PROTO_ADDR_MASK)) >> SNOR_PROTO_ADDR_SHIFT;
> +}
> +
> +static inline u8 spi_nor_get_protocol_data_nbits(enum spi_nor_protocol proto)
> +{
> +	return ((u32)(proto & SNOR_PROTO_DATA_MASK)) >> SNOR_PROTO_DATA_SHIFT;
> +}
> +
> +static inline u8 spi_nor_get_protocol_width(enum spi_nor_protocol proto)
> +{
> +	return spi_nor_get_protocol_data_nbits(proto);
> +}

[...]

Looks good otherwise.

-- 
Best regards,
Marek Vasut