Re: [PATCH v17 5/7] mtd: spi-nor: core: Track flash's internal address mode

[<Tudor.Ambarus@microchip.com>]

Hi, Takahiro,

Can I have your R-b tag on this patch, please?

Thanks,
ta

On 7/25/22 12:25, Tudor Ambarus wrote:
> We need to track the flash's internal address mode as there are flashes
> that can operate with 4B opcodes but unfortunately do not have a 4B opcode
> correspondent for all the 3B opcodes. Such an example is the Infineon
> Semper chips which provide 4B opcodes for read/program/erase but do not
> provide 4B opcodes for Read/Write Any Register. These registers are
> indexed by address and require the internal address mode of the flash
> before Read/Write Any Register opcodes are issued.
> 4B opcodes are preferred over changing the flash's address mode to 4byte,
> as set_4byte_addr_mode could be done in a non-volatile way and could break
> the boot sequence. Thus we need to track the flash's internal address mode
> so that we can use 4B opcodes together with opcodes that don't have a 4B
> opcode correspondent. Track flash's internal address mode.
> 
> addr_mode_nbytes is discovered when parsing BFPT. For the
> BFPT_DWORD1_ADDRESS_BYTES_3_OR_4 case, one could introduce a method that
> queries the flash's internal address mode at run-time (works for Winbond).
> If a run-time querying can not be accomplished or if SFDP is not defined
> at all, but the address mode is volatile and resets to a default known
> value at boot, one can change the default addr_mode_nbytes value of 3 by
> introducing a flash_info flag. If the address mode can not be queried,
> discovered and it is configured via a non-volatile register, we may
> introduce a dt property, but it will harm the generic approach of the
> jedec,spi-nor compatible. All this complexity is not needed now, so let it
> for future development.
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
>  drivers/mtd/spi-nor/core.h | 5 +++++
>  drivers/mtd/spi-nor/sfdp.c | 6 +++---
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index 7dc4cda41db3..85b0cf254e97 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -341,6 +341,10 @@ struct spi_nor_otp {
>   *			ECC unit size for ECC-ed flashes.
>   * @page_size:		the page size of the SPI NOR flash memory.
>   * @addr_nbytes:	number of address bytes to send.
> + * @addr_mode_nbytes:	number of address bytes of current address mode. Useful
> + *			when the flash operates with 4B opcodes but needs the
> + *			internal address mode for opcodes that don't have a 4B
> + *			opcode correspondent.
>   * @rdsr_dummy:		dummy cycles needed for Read Status Register command
>   *			in octal DTR mode.
>   * @rdsr_addr_nbytes:	dummy address bytes needed for Read Status Register
> @@ -374,6 +378,7 @@ struct spi_nor_flash_parameter {
>  	u32				writesize;
>  	u32				page_size;
>  	u8				addr_nbytes;
> +	u8				addr_mode_nbytes;
>  	u8				rdsr_dummy;
>  	u8				rdsr_addr_nbytes;
>  
> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
> index 3a48173a2d78..c7973368f5dc 100644
> --- a/drivers/mtd/spi-nor/sfdp.c
> +++ b/drivers/mtd/spi-nor/sfdp.c
> @@ -462,11 +462,11 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>  	switch (bfpt.dwords[BFPT_DWORD(1)] & BFPT_DWORD1_ADDRESS_BYTES_MASK) {
>  	case BFPT_DWORD1_ADDRESS_BYTES_3_ONLY:
>  	case BFPT_DWORD1_ADDRESS_BYTES_3_OR_4:
> -		params->addr_nbytes = 3;
> +		params->addr_mode_nbytes = params->addr_nbytes = 3;
>  		break;
>  
>  	case BFPT_DWORD1_ADDRESS_BYTES_4_ONLY:
> -		params->addr_nbytes = 4;
> +		params->addr_mode_nbytes = params->addr_nbytes = 4;
>  		break;
>  
>  	default:
> @@ -653,7 +653,7 @@ static u8 spi_nor_smpt_addr_nbytes(const struct spi_nor *nor, const u32 settings
>  		return 4;
>  	case SMPT_CMD_ADDRESS_LEN_USE_CURRENT:
>  	default:
> -		return nor->params->addr_nbytes;
> +		return nor->params->addr_mode_nbytes;
>  	}
>  }
>  


-- 
Cheers,
ta
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