[PATCH 1/5] mtd: spi-nor: spansion: Preserve CFR2V[7] when writing MEMLAT

[Tudor Ambarus]

On 6/12/23 11:04, tkuw584924 at gmail.com wrote:
> From: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
> 
> CFR2V[7] is assigned to Flash's address mode (3- or 4-ybte) and must not
> be changed when writing MEMLAT (CFR2V[3:0]). CFR2V must be read first,
> modified only CFR2V[3:0], then written back.

Last sentence could be reworded to "CFR2V shall be used in a read,
update, write back fashion."

Please specify in the commit message if this fixes a present bug or it's
just a prerequisite for the support that comes. The change is good but
we should be aware if you hit bugs or not.
> 
> Fixes: c3266af101f2 ("mtd: spi-nor: spansion: add support for Cypress Semper flash")
> Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
> Cc: stable at vger.kernel.org
> ---
>  drivers/mtd/spi-nor/spansion.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/spansion.c b/drivers/mtd/spi-nor/spansion.c
> index f2f4bc060f5e..7804be3a9f2a 100644
> --- a/drivers/mtd/spi-nor/spansion.c
> +++ b/drivers/mtd/spi-nor/spansion.c
> @@ -27,6 +27,7 @@
>  #define SPINOR_REG_CYPRESS_CFR2			0x3
>  #define SPINOR_REG_CYPRESS_CFR2V					\
>  	(SPINOR_REG_CYPRESS_VREG + SPINOR_REG_CYPRESS_CFR2)
> +#define SPINOR_REG_CYPRESS_CFR2_MEMLAT_MASK	GENMASK(3, 0)
>  #define SPINOR_REG_CYPRESS_CFR2_MEMLAT_11_24	0xb
>  #define SPINOR_REG_CYPRESS_CFR2_ADRBYT		BIT(7)
>  #define SPINOR_REG_CYPRESS_CFR3			0x4
> @@ -162,8 +163,17 @@ static int cypress_nor_octal_dtr_en(struct spi_nor *nor)
>  	int ret;
>  	u8 addr_mode_nbytes = nor->params->addr_mode_nbytes;
>  
> +	op = (struct spi_mem_op)
> +		CYPRESS_NOR_RD_ANY_REG_OP(addr_mode_nbytes,
> +					  SPINOR_REG_CYPRESS_CFR2V, 0, buf);
> +
> +	ret = spi_nor_read_any_reg(nor, &op, nor->reg_proto);
> +	if (ret)
> +		return ret;
> +
>  	/* Use 24 dummy cycles for memory array reads. */
> -	*buf = SPINOR_REG_CYPRESS_CFR2_MEMLAT_11_24;
> +	*buf &= ~SPINOR_REG_CYPRESS_CFR2_MEMLAT_MASK;
> +	*buf |= SPINOR_REG_CYPRESS_CFR2_MEMLAT_11_24;

Use FIELD_PREP please.

>  	op = (struct spi_mem_op)
>  		CYPRESS_NOR_WR_ANY_REG_OP(addr_mode_nbytes,
>  					  SPINOR_REG_CYPRESS_CFR2V, 1, buf);

Shall you zeroize the struct before using it again?