Re: [PATCH v4 13/20] mtd: spi-nor: Fix clearing of QE bit on lock()/unlock()

[Vignesh Raghavendra <vigneshr@ti.com>]

On 02-Nov-19 4:53 PM, Tudor.Ambarus@microchip.com wrote:
> From: Tudor Ambarus <tudor.ambarus@microchip.com>
> 
> Make sure that when doing a lock() or an unlock() operation we don't clear
> the QE bit from Status Register 2.
> 
> JESD216 revB or later offers information about the *default* Status
> Register commands to use (see BFPT DWORDS[15], bits 22:20). In this
> standard, Status Register 1 refers to the first data byte transferred on a
> Read Status (05h) or Write Status (01h) command. Status register 2 refers
> to the byte read using instruction 35h. Status register 2 is the second
> byte transferred in a Write Status (01h) command.
> 
> Industry naming and definitions of these Status Registers may differ.
> The definitions are described in JESD216B, BFPT DWORDS[15], bits 22:20.
> There are cases in which writing only one byte to the Status Register 1
> has the side-effect of clearing Status Register 2 and implicitly the Quad
> Enable bit. This side-effect is hit just by the
> BFPT_DWORD15_QER_SR2_BIT1_BUGGY and BFPT_DWORD15_QER_SR2_BIT1 cases.
>

But I see that 1 byte SR1 write still happens as part of
spi_nor_clear_sr_bp() until patch 20/20. So is this only a partial fix?
Should this patch be rearranged to appear along with 20/20?


> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 120 ++++++++++++++++++++++++++++++++++++++++--
>  include/linux/mtd/spi-nor.h   |   3 ++
>  2 files changed, 118 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 725dab241271..f96bc80c0ed1 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -959,12 +959,19 @@ static int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len)
>  	return spi_nor_wait_till_ready(nor);
>  }
>  
[...]
> +/**
>   * spi_nor_write_sr2() - Write the Status Register 2 using the
>   * SPINOR_OP_WRSR2 (3eh) command.
>   * @nor:	pointer to 'struct spi_nor'.
> @@ -3634,19 +3723,38 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>  		break;
>  
>  	case BFPT_DWORD15_QER_SR2_BIT1_BUGGY:
> +		/*
> +		 * Writing only one byte to the Status Register has the
> +		 * side-effect of clearing Status Register 2.
> +		 */
>  	case BFPT_DWORD15_QER_SR2_BIT1_NO_RD:
> +		/*
> +		 * Read Configuration Register (35h) instruction is not
> +		 * supported.
> +		 */
> +		nor->flags |= SNOR_F_HAS_16BIT_SR | SNOR_F_NO_READ_CR;

Since SNOR_F_HAS_16BIT_SR is set by default in
spi_nor_info_init_params(), no need to set the flag here again

>  		params->quad_enable = spansion_no_read_cr_quad_enable;
>  		break;
>  
>  	case BFPT_DWORD15_QER_SR1_BIT6:
> +		nor->flags &= ~SNOR_F_HAS_16BIT_SR;
>  		params->quad_enable = macronix_quad_enable;
>  		break;
>  
>  	case BFPT_DWORD15_QER_SR2_BIT7:
> +		nor->flags &= ~SNOR_F_HAS_16BIT_SR;
>  		params->quad_enable = sr2_bit7_quad_enable;
>  		break;
>  
>  	case BFPT_DWORD15_QER_SR2_BIT1:
> +		/*
> +		 * JESD216 rev B or later does not specify if writing only one
> +		 * byte to the Status Register clears or not the Status
> +		 * Register 2, so let's be cautious and keep the default
> +		 * assumption of a 16-bit Write Status (01h) command.
> +		 */
> +		nor->flags |= SNOR_F_HAS_16BIT_SR;
> +

Same here...

>  		params->quad_enable = spansion_read_cr_quad_enable;
>  		break;
>  
> @@ -4613,6 +4721,8 @@ static void spi_nor_info_init_params(struct spi_nor *nor)
>  	params->quad_enable = spansion_read_cr_quad_enable;
>  	params->set_4byte = spansion_set_4byte;
>  	params->setup = spi_nor_default_setup;
> +	/* Default to 16-bit Write Status (01h) Command */
> +	nor->flags |= SNOR_F_HAS_16BIT_SR;
>  
>  	/* Set SPI NOR sizes. */
>  	params->size = (u64)info->sector_size * info->n_sectors;
> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
> index d1d736d3c8ab..d6ec55cc6d97 100644
> --- a/include/linux/mtd/spi-nor.h
> +++ b/include/linux/mtd/spi-nor.h
> @@ -243,6 +243,9 @@ enum spi_nor_option_flags {
>  	SNOR_F_4B_OPCODES	= BIT(6),
>  	SNOR_F_HAS_4BAIT	= BIT(7),
>  	SNOR_F_HAS_LOCK		= BIT(8),
> +	SNOR_F_HAS_16BIT_SR	= BIT(9),
> +	SNOR_F_NO_READ_CR	= BIT(10),
> +
>  };
>  
>  /**
>