Re: [PATCH v2 2/3] mtd: spi-nor: add support to unlock flash device.

[Sagar Kadam]

On Tue, Apr 30, 2019 at 10:49 PM Paul Walmsley <paul.walmsley@xxxxxxxxxx> wrote:
>
> On Sun, 28 Apr 2019, Sagar Shrikant Kadam wrote:
>
> > Nor device (is25wp256 mounted on HiFive unleashed Rev A00 board) from ISSI
> > have memory blocks guarded by block protection bits BP[0,1,2,3].
> >
> > Clearing block protection bits,unlocks the flash memory regions
> > The unlock scheme is registered during nor scans.
>
> This also looks like it's partially based on Wes or Palmer's patch from
>
> https://github.com/riscv/riscv-linux/commit/c94e267766d62bc9a669611c3d0c8ed5ea26569b
>
> Please note that in the patch message.
Thank you Paul for pointing this out.
Yes,  I missed to add it to commit message and will submit a V3
version of the patch.

> > Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@xxxxxxxxxx>
> > ---
> >  drivers/mtd/spi-nor/spi-nor.c | 48 ++++++++++++++++++++++++++++++++++++++++++-
> >  include/linux/mtd/spi-nor.h   |  1 +
> >  2 files changed, 48 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> > index c5408ed..81c7b3e 100644
> > --- a/drivers/mtd/spi-nor/spi-nor.c
> > +++ b/drivers/mtd/spi-nor/spi-nor.c
> > @@ -1461,6 +1461,46 @@ static int macronix_quad_enable(struct spi_nor *nor)
> >  }
> >
> >  /**
> > + * issi_unlock() - clear BP[0123] write-protection.
> > + * @nor: pointer to a 'struct spi_nor'
> > + * @ofs: offset from which to unlock memory
> > + * @len: number of bytes to unlock
> > + * Bits [2345] of the Status Register are BP[0123].
> > + * ISSI chips use a different block protection scheme than other chips.
> > + * Just disable the write-protect unilaterally.
> > + * Return: 0 on success, -errno otherwise.
>
> This is closer to kernel-doc format, but not quite.  Please update this to
> align to
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/doc-guide/kernel-doc.rst#n57
>
This is a good pointer. I will align the function description
according to kernel-doc format.

>
> - Paul
>
> > + */
> > +static int issi_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
> > +{
> > +     int ret, val;
> > +     u8 mask = SR_BP0 | SR_BP1 | SR_BP2 | SR_BP3;
> > +
> > +     val = read_sr(nor);
> > +     if (val < 0)
> > +             return val;
> > +     if (!(val & mask))
> > +             return 0;
> > +
> > +     write_enable(nor);
> > +
> > +     write_sr(nor, val & ~mask);
> > +
> > +     ret = spi_nor_wait_till_ready(nor);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = read_sr(nor);
> > +     if (ret > 0 && !(ret & mask)) {
> > +             dev_info(nor->dev,
> > +                     "ISSI Block Protection Bits cleared SR=0x%x", ret);
> > +             return 0;
> > +     } else {
> > +             dev_err(nor->dev, "ISSI Block Protection Bits not cleared\n");
> > +             return -EINVAL;
> > +     }
> > +}
> > +
> > +/**
> >   * spansion_quad_enable() - set QE bit in Configuraiton Register.
> >   * @nor:     pointer to a 'struct spi_nor'
> >   *
> > @@ -1836,7 +1876,7 @@ static int sr2_bit7_quad_enable(struct spi_nor *nor)
> >                       SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },
> >       { "is25wp256", INFO(0x9d7019, 0, 64 * 1024, 1024,
> >                       SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
> > -                     SPI_NOR_4B_OPCODES)
> > +                     SPI_NOR_4B_OPCODES | SPI_NOR_HAS_LOCK)
> >       },
> >
> >       /* Macronix */
> > @@ -4078,6 +4118,12 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
> >               nor->flash_is_locked = stm_is_locked;
> >       }
> >
> > +     /* NOR protection support for ISSI chips */
> > +     if (JEDEC_MFR(info) == SNOR_MFR_ISSI ||
> > +         info->flags & SPI_NOR_HAS_LOCK) {
> > +             nor->flash_unlock = issi_unlock;
> > +
> > +     }
> >       if (nor->flash_lock && nor->flash_unlock && nor->flash_is_locked) {
> >               mtd->_lock = spi_nor_lock;
> >               mtd->_unlock = spi_nor_unlock;
> > diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
> > index ff13297..9a7d719 100644
> > --- a/include/linux/mtd/spi-nor.h
> > +++ b/include/linux/mtd/spi-nor.h
> > @@ -127,6 +127,7 @@
> >  #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 for ISSI device*/
> >  #define SR_TB                        BIT(5)  /* Top/Bottom protect */
> >  #define SR_SRWD                      BIT(7)  /* SR write protect */
> >  /* Spansion/Cypress specific status bits */
> > --
> > 1.9.1
> >
> >