[PATCH] mtd: spi-nor: Check that BP bits are set properly

[Cyrille Pitchen]

Hi Aaron,

Le 29/10/2017 à 17:11, Aaron Sierra a écrit :
> Previously, the lock and unlock functions returned success even if the
> BP bits were not actually updated in the status register due to
> hardware write protection. Introduce write_sr_and_check() to write and
> read back the status register to ensure the desired BP bits are
> actually set as requested.
> 
> Signed-off-by: Joe Schultz <jschultz at xes-inc.com>
> Signed-off-by: Aaron Sierra <asierra at xes-inc.com>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 39 +++++++++++++++++++++++++++------------
>  1 file changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 19c00072..8a87bd1 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -550,6 +550,31 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
>  	return ret;
>  }
>  
> +/* Write status register and ensure bits in mask match written values */
> +static int write_sr_and_check(struct spi_nor *nor, u8 new, u8 mask)

Maybe keep the previous name 'status_new' to be consistent with stm_lock()
and stm_unlock() and also because 'new' is a C++ reserved keyword so it might
be better to avoid using it to name some variable (editor syntax coloring issue
for instance).

> +{
> +	int ret;
> +
> +	ret = spi_nor_wait_till_ready(nor);
> +	if (ret)
> +		return ret;
> +

Why do you poll the status register here ?
Based on the source code before your patch, it should not be needed.
Do you think it is ?

Otherwise, your patch looks good to me :)

Best regards,

Cyrille

> +	write_enable(nor);
> +	ret = write_sr(nor, new);
> +	if (ret)
> +		return ret;
> +
> +	ret = spi_nor_wait_till_ready(nor);
> +	if (ret)
> +		return ret;
> +
> +	ret = read_sr(nor);
> +	if (ret < 0)
> +		return ret;
> +
> +	return ((ret & mask) != (new & mask)) ? -EIO : 0;
> +}
> +
>  static void stm_get_locked_range(struct spi_nor *nor, u8 sr, loff_t *ofs,
>  				 uint64_t *len)
>  {
> @@ -648,7 +673,6 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
>  	loff_t lock_len;
>  	bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB;
>  	bool use_top;
> -	int ret;
>  
>  	status_old = read_sr(nor);
>  	if (status_old < 0)
> @@ -712,11 +736,7 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
>  	if ((status_new & mask) < (status_old & mask))
>  		return -EINVAL;
>  
> -	write_enable(nor);
> -	ret = write_sr(nor, status_new);
> -	if (ret)
> -		return ret;
> -	return spi_nor_wait_till_ready(nor);
> +	return write_sr_and_check(nor, status_new, mask);
>  }
>  
>  /*
> @@ -733,7 +753,6 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
>  	loff_t lock_len;
>  	bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB;
>  	bool use_top;
> -	int ret;
>  
>  	status_old = read_sr(nor);
>  	if (status_old < 0)
> @@ -800,11 +819,7 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
>  	if ((status_new & mask) > (status_old & mask))
>  		return -EINVAL;
>  
> -	write_enable(nor);
> -	ret = write_sr(nor, status_new);
> -	if (ret)
> -		return ret;
> -	return spi_nor_wait_till_ready(nor);
> +	return write_sr_and_check(nor, status_new, mask);
>  }
>  
>  /*
>