linux-kernel - Re: [PATCH v2 02/14] mtd: spinand: Add enum spinand

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Message-ID: <20211012083906.30c50009@collabora.com>
Date:   Tue, 12 Oct 2021 08:39:06 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Apurva Nandan <a-nandan@...com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>,
        Patrice Chotard <patrice.chotard@...s.st.com>,
        Christophe Kerello <christophe.kerello@...s.st.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <p.yadav@...com>
Subject: Re: [PATCH v2 02/14] mtd: spinand: Add enum spinand_proto to
 indicate current SPI IO mode

On Tue, 12 Oct 2021 02:16:07 +0530
Apurva Nandan <a-nandan@...com> wrote:

> Unlike Dual and Quad SPI modes flashes, Octal DTR SPI NAND flashes
> require all instructions to be made in 8D-8D-8D protocol when the
> flash is in Octal DTR mode. Hence, storing the current SPI IO mode
> becomes necessary for correctly generating non-array access operations.
> 
> Store the current SPI IO mode in the spinand struct using a reg_proto
> enum. This would act as a flag, denoting that the core should use
> the given SPI protocol for non-page access operations.
> 
> Also provide basic macros for extracting buswidth and dtr mode
> information from the spinand_proto enum.
> 
> Signed-off-by: Apurva Nandan <a-nandan@...com>
> ---
>  drivers/mtd/nand/spi/core.c |  2 ++
>  include/linux/mtd/spinand.h | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 2c8685f1f2fa..d82a3e6d9bb5 100644
> --- a/drivers/mtd/nand/spi/core.c
> +++ b/drivers/mtd/nand/spi/core.c
> @@ -1155,6 +1155,7 @@ static void spinand_mtd_resume(struct mtd_info *mtd)
>  	struct spinand_device *spinand = mtd_to_spinand(mtd);
>  	int ret;
>  
> +	spinand->reg_proto = SPINAND_SINGLE_STR;
>  	ret = spinand_reset_op(spinand);
>  	if (ret)
>  		return;
> @@ -1181,6 +1182,7 @@ static int spinand_init(struct spinand_device *spinand)
>  	if (!spinand->scratchbuf)
>  		return -ENOMEM;
>  
> +	spinand->reg_proto = SPINAND_SINGLE_STR;
>  	ret = spinand_detect(spinand);
>  	if (ret)
>  		goto err_free_bufs;
> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
> index 6988956b8492..f6093cd98d7b 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -140,6 +140,31 @@
>  		   SPI_MEM_OP_NO_DUMMY,					\
>  		   SPI_MEM_OP_DATA_OUT(len, buf, 4))
>  
> +#define SPINAND_PROTO_BUSWIDTH_MASK	GENMASK(6, 0)
> +#define SPINAND_PROTO_DTR_BIT		BIT(7)
> +
> +#define SPINAND_PROTO_STR(__buswidth)	\
> +	((u8)(((__buswidth) - 1) & SPINAND_PROTO_BUSWIDTH_MASK))
> +#define SPINAND_PROTO_DTR(__buswidth)	\
> +	(SPINAND_PROTO_DTR_BIT | SPINAND_PROTO_STR(__buswidth))
> +
> +#define SPINAND_PROTO_BUSWIDTH(__proto)	\
> +	((u8)(((__proto) & SPINAND_PROTO_BUSWIDTH_MASK) + 1))
> +#define SPINAND_PROTO_IS_DTR(__proto)	(!!((__proto) & SPINAND_PROTO_DTR_BIT))
> +
> +/**
> + * enum spinand_proto - List allowable SPI protocol variants for read reg,
> + *			write reg, blk erase, write enable/disable, page read
> + *			and program exec operations.
> + */
> +enum spinand_proto {

s/spinand_proto/spinand_protocol/

> +	SPINAND_SINGLE_STR = SPINAND_PROTO_STR(1),
> +	SPINAND_DUAL_STR = SPINAND_PROTO_STR(2),
> +	SPINAND_QUAD_STR = SPINAND_PROTO_STR(4),
> +	SPINAND_OCTAL_STR = SPINAND_PROTO_STR(8),
> +	SPINAND_OCTAL_DTR = SPINAND_PROTO_DTR(8),

Why not have a contiguous enum listing all the modes? Are you extracting
the buswidth from these values?

> +};
> +
>  /**
>   * Standard SPI NAND flash commands
>   */
> @@ -407,6 +432,9 @@ struct spinand_dirmap {
>   *		   this die. Only required if your chip exposes several dies
>   * @cur_target: currently selected target/die
>   * @eccinfo: on-die ECC information
> + * @reg_proto: select a variant of SPI IO protocol (single, quad, octal or
> + *	       octal DTR) for read_reg/write_reg/erase operations. Update on
> + *	       successful transition into a different SPI IO protocol.
>   * @cfg_cache: config register cache. One entry per die
>   * @databuf: bounce buffer for data
>   * @oobbuf: bounce buffer for OOB data
> @@ -438,6 +466,8 @@ struct spinand_device {
>  
>  	struct spinand_ecc_info eccinfo;
>  
> +	enum spinand_proto reg_proto;
> +

I guess this mode will apply to all sort of commands, not just reg
accesses, so why not name it protocol or mode?

>  	u8 *cfg_cache;
>  	u8 *databuf;
>  	u8 *oobbuf;