Re: [PATCH 3/5] mtd: spi-nor: add Global Block Unlock support

[Vignesh Raghavendra]

On 17/07/19 2:18 PM, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
> From: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
> 
> To avoid inadvertent writes during power-up, some flashes are
> write-protected by default after a power-on reset cycle.
> A Global Block-Protection Unlock command offers a single
> command cycle that unlocks the entire memory array. This is
> identical with what other nor flashes are doing by clearing
> the block protection bits from the status register: disable
> the write protection after a power-on reset cycle.
> 
> We can't determine this purely by manufacturer type and it's not
> autodetectable by anything like SFDP, so make a new flag for it:
> UNLOCK_GLOBAL_BLOCK.
> 
> Note that the Global Block Unlock command has different names
> depending on the manufacturer, but always the same command value:
> 0x98. Macronix's MX25U12835F names it Gang Block Unlock,
> Winbound's W25Q128FV names it Global Block Unlock and
> Microchip's SST26VF064B names it Global Block Protection Unlock.
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

Reviewed-by: Vignesh Raghavendra <vigneshr@xxxxxx>


> ---
>  drivers/mtd/spi-nor/spi-nor.c | 21 ++++++++++++++++++++-
>  include/linux/mtd/spi-nor.h   |  1 +
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index e9e441f91b68..767e2e6eb1b8 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -250,7 +250,7 @@ struct flash_info {
>  	u16		page_size;
>  	u16		addr_width;
>  
> -	u16		flags;
> +	u32		flags;
>  #define SECT_4K			BIT(0)	/* SPINOR_OP_BE_4K works uniformly */
>  #define SPI_NOR_NO_ERASE	BIT(1)	/* No erase command needed */
>  #define SST_WRITE		BIT(2)	/* use SST byte programming */
> @@ -279,6 +279,7 @@ struct flash_info {
>  #define SPI_NOR_SKIP_SFDP	BIT(13)	/* Skip parsing of SFDP tables */
>  #define USE_CLSR		BIT(14)	/* use CLSR command */
>  #define SPI_NOR_OCTAL_READ	BIT(15)	/* Flash supports Octal Read */
> +#define UNLOCK_GLOBAL_BLOCK	BIT(16) /* Unlock global block protection */
>  
>  	/* Part specific fixup hooks. */
>  	const struct spi_nor_fixups *fixups;
> @@ -1725,6 +1726,20 @@ static int spi_nor_spansion_clear_sr_bp(struct spi_nor *nor)
>  	return spi_nor_clear_sr_bp(nor);
>  }
>  
> +static int spi_nor_unlock_global_block_protection(struct spi_nor *nor)
> +{
> +	int ret;
> +
> +	write_enable(nor);
> +
> +	ret = nor->write_reg(nor, SPINOR_OP_ULBPR, NULL, 0);
> +	if (ret < 0) {
> +		dev_err(nor->dev, "error %d on ULBPR\n", ret);
> +		return ret;
> +	}
> +	return spi_nor_wait_till_ready(nor);
> +}
> +
>  /* Used when the "_ext_id" is two bytes at most */
>  #define INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags)	\
>  		.id = {							\
> @@ -4053,6 +4068,10 @@ static int spi_nor_init(struct spi_nor *nor)
>  				spi_nor_spansion_clear_sr_bp;
>  	}
>  
> +	if (nor->info->flags & UNLOCK_GLOBAL_BLOCK)
> +		nor->disable_write_protection =
> +			spi_nor_unlock_global_block_protection;
> +
>  	if (nor->disable_write_protection) {
>  		err = nor->disable_write_protection(nor);
>  		if (err) {
> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
> index 6c3273760700..84d279fd287e 100644
> --- a/include/linux/mtd/spi-nor.h
> +++ b/include/linux/mtd/spi-nor.h
> @@ -65,6 +65,7 @@
>  #define SPINOR_OP_CLFSR		0x50	/* Clear flag status register */
>  #define SPINOR_OP_RDEAR		0xc8	/* Read Extended Address Register */
>  #define SPINOR_OP_WREAR		0xc5	/* Write Extended Address Register */
> +#define SPINOR_OP_ULBPR		0x98    /* Global Block Unlock Protection */
>  
>  /* 4-byte address opcodes - used on Spansion and some Macronix flashes. */
>  #define SPINOR_OP_READ_4B	0x13	/* Read data bytes (low frequency) */
> 

-- 
Regards
Vignesh