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Date:   Fri, 23 Dec 2016 19:56:36 +0100
From:   Marek Vasut <marek.vasut@...il.com>
To:     Cyrille Pitchen <cyrille.pitchen@...el.com>
Cc:     computersforpeace@...il.com, boris.brezillon@...e-electrons.com,
        richard@....at, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, broonie@...nel.org,
        linux-spi@...r.kernel.org
Subject: Re: [PATCH v3 2/2] mtd: spi-nor: add a stateless method to support
 memory size above 128Mib

On 12/19/2016 04:05 PM, Cyrille Pitchen wrote:
> This patch provides an alternative mean to support memory above 16MiB
> (128Mib) by replacing 3byte address op codes by their associated 4byte
> address versions.
> 
> Using the dedicated 4byte address op codes doesn't change the internal
> state of the SPI NOR memory as opposed to using other means such as
> updating a Base Address Register (BAR) and sending command to enter/leave
> the 4byte mode.
> 
> Hence when a CPU reset occurs, early bootloaders don't need to be aware
> of BAR value or 4byte mode being enabled: they can still access the first
> 16MiB of the SPI NOR memory using the regular 3byte address op codes.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...el.com>
> Tested-by: Vignesh R <vigneshr@...com>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 101 +++++++++++++++++++++++++++++++++---------
>  1 file changed, 80 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 9bb8f91fa42e..a5120fd7095e 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -81,6 +81,10 @@ struct flash_info {
>  					 * because it has the same value as
>  					 * ATMEL flashes)
>  					*/
> +#define SPI_NOR_4B_OPCODES	BIT(11)	/*
> +					 * Use dedicated 4byte address op codes
> +					 * to support memory size above 128Mib.
> +					 */
>  };
>  
>  #define JEDEC_MFR(info)	((info)->id[0])
> @@ -194,6 +198,78 @@ static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)
>  	return mtd->priv;
>  }
>  
> +
> +static u8 spi_nor_convert_opcode(u8 opcode, const u8 table[][2])
> +{
> +	size_t i;
> +
> +	for (i = 0; table[i][0]; ++i)

i++ :)

> +		if (table[i][0] == opcode)
> +			return table[i][1];

This code just waits for some nice SPI NOR to introduce opcode 0x0 I
think. Wouldn't it be better to use ARRAY_SIZE() instead and pass the
result of it into this function ?

> +	/* No conversion found, keep input op code. */
> +	return opcode;
> +}
> +
> +static inline u8 spi_nor_convert_3to4_read(u8 opcode)
> +{
> +	static const u8 spi_nor_3to4_read[][2] = {
> +		{ SPINOR_OP_READ,	SPINOR_OP_READ_4B },
> +		{ SPINOR_OP_READ_FAST,	SPINOR_OP_READ_FAST_4B },
> +		{ SPINOR_OP_READ_1_1_2,	SPINOR_OP_READ_1_1_2_4B },
> +		{ SPINOR_OP_READ_1_2_2,	SPINOR_OP_READ_1_2_2_4B },
> +		{ SPINOR_OP_READ_1_1_4,	SPINOR_OP_READ_1_1_4_4B },
> +		{ SPINOR_OP_READ_1_4_4,	SPINOR_OP_READ_1_4_4_4B },
> +		{0, 0}
> +	};
> +
> +	return spi_nor_convert_opcode(opcode, spi_nor_3to4_read);
> +}
> +
> +static inline u8 spi_nor_convert_3to4_program(u8 opcode)
> +{
> +	static const u8 spi_nor_3to4_program[][2] = {
> +		{ SPINOR_OP_PP,		SPINOR_OP_PP_4B },
> +		{ SPINOR_OP_PP_1_1_4,	SPINOR_OP_PP_1_1_4_4B },
> +		{ SPINOR_OP_PP_1_4_4,	SPINOR_OP_PP_1_4_4_4B },
> +		{0, 0}
> +	};
> +
> +	return spi_nor_convert_opcode(opcode, spi_nor_3to4_program);
> +}
> +
> +static inline u8 spi_nor_convert_3to4_erase(u8 opcode)
> +{
> +	static const u8 spi_nor_3to4_erase[][2] = {
> +		{ SPINOR_OP_BE_4K,	SPINOR_OP_BE_4K_4B },
> +		{ SPINOR_OP_BE_32K,	SPINOR_OP_BE_32K_4B },
> +		{ SPINOR_OP_SE,		SPINOR_OP_SE_4B },
> +		{0, 0}
> +	};
> +
> +	return spi_nor_convert_opcode(opcode, spi_nor_3to4_erase);
> +}
> +
> +static void spi_nor_set_4byte_opcodes(struct spi_nor *nor,
> +				      const struct flash_info *info)
> +{
> +	/* Do some manufacturer fixups first */
> +	switch (JEDEC_MFR(info)) {
> +	case SNOR_MFR_SPANSION:
> +		/* No small sector erase for 4-byte command set */
> +		nor->erase_opcode = SPINOR_OP_SE;
> +		nor->mtd.erasesize = info->sector_size;
> +		break;
> +
> +	default:
> +		break;
> +	}
> +
> +	nor->read_opcode = spi_nor_convert_3to4_read(nor->read_opcode);
> +	nor->program_opcode = spi_nor_convert_3to4_program(nor->program_opcode);
> +	nor->erase_opcode = spi_nor_convert_3to4_erase(nor->erase_opcode);
> +}
> +
>  /* Enable/disable 4-byte addressing mode. */
>  static inline int set_4byte(struct spi_nor *nor, const struct flash_info *info,
>  			    int enable)
> @@ -1621,27 +1697,10 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>  	else if (mtd->size > 0x1000000) {
>  		/* enable 4-byte addressing if the device exceeds 16MiB */
>  		nor->addr_width = 4;
> -		if (JEDEC_MFR(info) == SNOR_MFR_SPANSION) {
> -			/* Dedicated 4-byte command set */
> -			switch (nor->flash_read) {
> -			case SPI_NOR_QUAD:
> -				nor->read_opcode = SPINOR_OP_READ_1_1_4_4B;
> -				break;
> -			case SPI_NOR_DUAL:
> -				nor->read_opcode = SPINOR_OP_READ_1_1_2_4B;
> -				break;
> -			case SPI_NOR_FAST:
> -				nor->read_opcode = SPINOR_OP_READ_FAST_4B;
> -				break;
> -			case SPI_NOR_NORMAL:
> -				nor->read_opcode = SPINOR_OP_READ_4B;
> -				break;
> -			}
> -			nor->program_opcode = SPINOR_OP_PP_4B;
> -			/* No small sector erase for 4-byte command set */
> -			nor->erase_opcode = SPINOR_OP_SE_4B;
> -			mtd->erasesize = info->sector_size;
> -		} else
> +		if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
> +		    info->flags & SPI_NOR_4B_OPCODES)
> +			spi_nor_set_4byte_opcodes(nor, info);
> +		else
>  			set_4byte(nor, info, 1);
>  	} else {
>  		nor->addr_width = 3;
> 


-- 
Best regards,
Marek Vasut

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