Re: [PATCH v2 2/3] mtd: spi-nor: add 4bit block protection support

[Michael Walle <michael@walle.cc>]

Hi Jungseung,

Am 2020-03-18 13:06, schrieb Jungseung Lee:
> Currently, we are supporting block protection only for flash chips with
> 3 block protection bits in the SR register.
> 
> This patch enables block protection support for flashes with 4 block
> protection bits(bp0-3).
> 
> Added a flag to inform that this flash has 4 block protection bit,
> and added another flag for some flashes in which bp3 bit is not 
> adjacent
> to other bp bits.
> 
> Signed-off-by: Jungseung Lee <js07.lee@samsung.com>

Please add a changelog if you're doing a new patch version. This will
greatly ease the review.


> ---
>  drivers/mtd/spi-nor/core.c  | 62 ++++++++++++++++++++++++++++++++++---
>  drivers/mtd/spi-nor/core.h  | 10 ++++++
>  include/linux/mtd/spi-nor.h |  2 ++
>  3 files changed, 69 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index e4ed8553aae8..842e2fabdb20 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -1516,7 +1516,15 @@ static int spi_nor_erase(struct mtd_info *mtd,
> struct erase_info *instr)
> 
>  static u8 spi_nor_get_bp_mask(struct spi_nor *nor)
>  {
> -	return SR_BP2 | SR_BP1 | SR_BP0;
> +	u8 mask = SR_BP2 | SR_BP1 | SR_BP0;
> +
> +	if (nor->flags & SNOR_F_HAS_SR_BP3_BIT6)
> +		return mask | SR_BP3_BIT6;
> +
> +	if (nor->flags & SNOR_F_HAS_4BIT_BP)
> +		return mask | SR_BP3;
> +
> +	return mask;
>  }
> 
>  static u8 spi_nor_get_tb_mask(struct spi_nor *nor)
> @@ -1532,7 +1540,8 @@ static int spi_nor_get_min_prot_length(struct
> spi_nor *nor)
>  	int bp_slots, bp_slots_needed;
>  	u8 mask = spi_nor_get_bp_mask(nor);
> 
> -	bp_slots = (mask >> SR_BP_SHIFT) + 1;
> +	/* 2 ^ number_of_bp_bit slots available */
> +	bp_slots = 1 << hweight8(mask);
> 
>  	/* Reserved one for "protect none" and one for "protect all". */
>  	bp_slots = bp_slots - 2;
> @@ -1553,7 +1562,12 @@ static void spi_nor_get_locked_range_sr(struct
> spi_nor *nor, u8 sr, loff_t *ofs,
>  	int min_prot_len;
>  	u8 mask = spi_nor_get_bp_mask(nor);
>  	u8 tb_mask = spi_nor_get_tb_mask(nor);
> -	u8 bp = (sr & mask) >> SR_BP_SHIFT;
> +	u8 bp, val = sr & mask;
> +


you could add a comment here. It is not obvious why one don't need
to check nor->flags & SNOR_F_HAS_SR_BP3_BIT6. Ie. it is already
masked with mask retrieved from spi_nor_get_bp_mask() which makes
sure the SR_BP3_BIT6 may only be set if nor->flags contains that
specific flag. Or just be explicit and do

if (nor->flags & SNOR_F_HAS_SR_BP3_BIT6 && val & SR_BP3_BIT6)

I'd prefer the latter because
  (1) its the same as you've done it below
  (2) its easier to understand in the future

That being said. Nice work! So if you do a respin with that you
can add:
Reviewed-by: Michael Walle <michael@walle.cc>

Tested with a MX25U3232F (no upstream support yet).

Tested-by: Michael Walle <michael@walle.cc>

> +	if (val & SR_BP3_BIT6)
> +		val = (val & ~SR_BP3_BIT6) | SR_BP3;
> +
> +	bp = val >> SR_BP_SHIFT;
> 
>  	if (!bp) {
>  		/* No protection */
> @@ -1611,7 +1625,7 @@ static int spi_nor_is_unlocked_sr(struct spi_nor
> *nor, loff_t ofs, uint64_t len,
> 
>  /*
>   * Lock a region of the flash. Compatible with ST Micro and similar 
> flash.
> - * Supports the block protection bits BP{0,1,2} in the status register
> + * Supports the block protection bits BP{0,1,2}/BP{0,1,2,3} in the
> status register
>   * (SR). Does not support these features found in newer SR bitfields:
>   *   - SEC: sector/block protect - only handle SEC=0 (block protect)
>   *   - CMP: complement protect - only support CMP=0 (range is not 
> complemented)
> @@ -1619,7 +1633,7 @@ static int spi_nor_is_unlocked_sr(struct spi_nor
> *nor, loff_t ofs, uint64_t len,
>   * Support for the following is provided conditionally for some flash:
>   *   - TB: top/bottom protect
>   *
> - * Sample table portion for 8MB flash (Winbond w25q64fw):
> + * Sample table portion for 8MB flash (Winbond w25q64fw / BP0-2):
>   *
>   *   SEC  |  TB   |  BP2  |  BP1  |  BP0  |  Prot Length  | Protected 
> Portion
>   *  
> --------------------------------------------------------------------------
> @@ -1639,6 +1653,32 @@ static int spi_nor_is_unlocked_sr(struct
> spi_nor *nor, loff_t ofs, uint64_t len,
>   *    0   |   1   |   1   |   0   |   1   |  2 MB         | Lower 1/4
>   *    0   |   1   |   1   |   1   |   0   |  4 MB         | Lower 1/2
>   *
> + * Sample table portion for 64MB flash (Micron n25q512ax3 / BP0-3):
> + *
> + *   TB   |  BP3  |  BP2  |  BP1  |  BP0  |  Prot Length  | Protected 
> Portion
> + *  
> --------------------------------------------------------------------------
> + *    0   |   0   |   0   |   0   |   0   |  NONE         | NONE
> + *    0   |   0   |   0   |   0   |   1   |   64 KB       | Upper 
> 1/1024
> + *    0   |   0   |   0   |   1   |   0   |  128 KB       | Upper 
> 1/512
> + *    0   |   0   |   0   |   1   |   1   |  256 KB       | Upper 
> 1/256
> + *   ...
> + *    0   |   1   |   0   |   0   |   1   |  16 MB        | Upper 1/4
> + *    0   |   1   |   0   |   1   |   0   |  32 MB        | Upper 1/2
> + *    0   |   1   |   0   |   1   |   1   |  64 MB        | ALL
> + *    0   |   1   |   1   |   0   |   0   |  64 MB        | ALL
> + *   ...
> + *  
> ------|-------|-------|-------|-------|---------------|-------------------
> + *    1   |   0   |   0   |   0   |   0   |   NONE        | NONE
> + *    1   |   0   |   0   |   0   |   1   |   64 KB       | Lower 
> 1/1024
> + *    1   |   0   |   0   |   1   |   0   |  128 KB       | Lower 
> 1/512
> + *    1   |   0   |   0   |   1   |   1   |  256 KB       | Lower 
> 1/256
> + *   ...
> + *    1   |   1   |   0   |   0   |   1   |  16 MB        | Lower 1/4
> + *    1   |   1   |   0   |   1   |   0   |  32 MB        | Lower 1/2
> + *    1   |   1   |   0   |   1   |   1   |  64 MB        | ALL
> + *    1   |   1   |   1   |   0   |   0   |  64 MB        | ALL
> + *   ...
> + *
>   * Returns negative on errors, 0 on success.
>   */
>  static int spi_nor_sr_lock(struct spi_nor *nor, loff_t ofs, uint64_t 
> len)
> @@ -1690,6 +1730,9 @@ static int spi_nor_sr_lock(struct spi_nor *nor,
> loff_t ofs, uint64_t len)
>  		min_prot_len = spi_nor_get_min_prot_length(nor);
>  		pow = ilog2(lock_len) - ilog2(min_prot_len) + 1;
>  		val = pow << SR_BP_SHIFT;
> +
> +		if (nor->flags & SNOR_F_HAS_SR_BP3_BIT6 && val & SR_BP3)
> +			val = (val & ~SR_BP3) | SR_BP3_BIT6;
>  	}
> 
>  	if (val & ~mask)
> @@ -1772,6 +1815,9 @@ static int spi_nor_sr_unlock(struct spi_nor
> *nor, loff_t ofs, uint64_t len)
>  		pow = ilog2(lock_len) - ilog2(min_prot_len) + 1;
>  		val = pow << SR_BP_SHIFT;
> 
> +		if (nor->flags & SNOR_F_HAS_SR_BP3_BIT6 && val & SR_BP3)
> +			val = (val & ~SR_BP3) | SR_BP3_BIT6;
> +
>  		/* Some power-of-two sizes are not supported */
>  		if (val & ~mask)
>  			return -EINVAL;
> @@ -3131,6 +3177,12 @@ int spi_nor_scan(struct spi_nor *nor, const char 
> *name,
>  	if (info->flags & USE_CLSR)
>  		nor->flags |= SNOR_F_USE_CLSR;
> 
> +	if (info->flags & SPI_NOR_4BIT_BP) {
> +		nor->flags |= SNOR_F_HAS_4BIT_BP;
> +		if (info->flags & SPI_NOR_BP3_SR_BIT6)
> +			nor->flags |= SNOR_F_HAS_SR_BP3_BIT6;
> +	}
> +
>  	if (info->flags & SPI_NOR_NO_ERASE)
>  		mtd->flags |= MTD_NO_ERASE;
> 
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index 3ce826b35ad1..6f2f6b27173f 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -24,6 +24,8 @@ enum spi_nor_option_flags {
>  	SNOR_F_HAS_16BIT_SR	= BIT(9),
>  	SNOR_F_NO_READ_CR	= BIT(10),
>  	SNOR_F_HAS_SR_TB_BIT6	= BIT(11),
> +	SNOR_F_HAS_4BIT_BP      = BIT(12),
> +	SNOR_F_HAS_SR_BP3_BIT6  = BIT(13),
>  };
> 
>  struct spi_nor_read_command {
> @@ -301,6 +303,14 @@ struct flash_info {
>  					 * status register. Must be used with
>  					 * SPI_NOR_HAS_TB.
>  					 */
> +#define SPI_NOR_4BIT_BP		BIT(17) /*
> +					 * Flash SR has 4 bit fields (BP0-3)
> +					 * for block protection.
> +					 */
> +#define SPI_NOR_BP3_SR_BIT6	BIT(18) /*
> +					 * BP3 is bit 6 of status register.
> +					 * Must be used with SPI_NOR_4BIT_BP.
> +					 */
> 
>  	/* Part specific fixup hooks. */
>  	const struct spi_nor_fixups *fixups;
> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
> index e656858b50a5..1e2af0ec1f03 100644
> --- a/include/linux/mtd/spi-nor.h
> +++ b/include/linux/mtd/spi-nor.h
> @@ -111,7 +111,9 @@
>  #define SR_BP0			BIT(2)	/* Block protect 0 */
>  #define SR_BP1			BIT(3)	/* Block protect 1 */
>  #define SR_BP2			BIT(4)	/* Block protect 2 */
> +#define SR_BP3			BIT(5)	/* Block protect 3 */
>  #define SR_TB_BIT5		BIT(5)	/* Top/Bottom protect */
> +#define SR_BP3_BIT6		BIT(6)	/* Block protect 3 */
>  #define SR_TB_BIT6		BIT(6)	/* Top/Bottom protect */
>  #define SR_SRWD			BIT(7)	/* SR write protect */
>  /* Spansion/Cypress specific status bits */

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