linux-kernel - Re: [PATCH v2 2/2] mtd: spi-nor: sst: Add support for Global Unlock on sst26vf

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Message-ID: <b3a61abec8927c7229c27415d2c769a8@walle.cc>
Date:   Wed, 20 Jan 2021 15:05:22 +0100
From:   Michael Walle <michael@...le.cc>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc:     vigneshr@...com, p.yadav@...com, miquel.raynal@...tlin.com,
        richard@....at, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Kavyasree.Kotagiri@...rochip.com
Subject: Re: [PATCH v2 2/2] mtd: spi-nor: sst: Add support for Global Unlock
 on sst26vf

Am 2021-01-20 14:19, schrieb Tudor Ambarus:
> Even if sst26vf shares the SPINOR_OP_GBULK opcode with
> Macronix (ex. MX25U12835F) and Winbound (ex. W25Q128FV),
> it has its own Individual Block Protection scheme, which
> is also capable to read-lock individual parameter blocks.
> Thus the sst26vf's Individual Block Protection scheme will
> reside in the sst.c manufacturer driver.
> 
> Add support to unlock the entire flash memory. The device
> is write-protected by default after a power-on reset cycle
> (volatile software protection), in order to avoid inadvertent
> writes during power-up. Could do an erase, write, read back,
> and compare when MTD_SPI_NOR_SWP_DISABLE_ON_VOLATILE=y.
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
> ---

Damn, who on earth assigned the "block protection" bits to the
8/32/64kb sectors on the flash (SST26VF064B DS, Table 5-6). That is
nuts.

Except one comment below:

Reviewed-by: Michael Walle <michael@...le.cc>

> v2: s/!ofs/ofs == 0/
> 
>  drivers/mtd/spi-nor/sst.c | 38 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
> index 00e48da0744a..d6e1396abb96 100644
> --- a/drivers/mtd/spi-nor/sst.c
> +++ b/drivers/mtd/spi-nor/sst.c
> @@ -8,6 +8,39 @@
> 
>  #include "core.h"
> 
> +static int sst26vf_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static int sst26vf_unlock(struct spi_nor *nor, loff_t ofs, uint64_t 
> len)
> +{
> +	if (ofs == 0 && len == nor->params->size)
> +		return spi_nor_global_block_unlock(nor);


Some blocks might not be unlocked because they are permanently
locked. Does it make sense to read BPNV of the control register
and add a debug message here?

-michael

> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static int sst26vf_is_locked(struct spi_nor *nor, loff_t ofs, uint64_t 
> len)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static const struct spi_nor_locking_ops sst26vf_locking_ops = {
> +	.lock = sst26vf_lock,
> +	.unlock = sst26vf_unlock,
> +	.is_locked = sst26vf_is_locked,
> +};
> +
> +static void sst26vf_default_init(struct spi_nor *nor)
> +{
> +	nor->params->locking_ops = &sst26vf_locking_ops;
> +}
> +
> +static const struct spi_nor_fixups sst26vf_fixups = {
> +	.default_init = sst26vf_default_init,
> +};
> +
>  static const struct flash_info sst_parts[] = {
>  	/* SST -- large erase sizes are "overlays", "sectors" are 4K */
>  	{ "sst25vf040b", INFO(0xbf258d, 0, 64 * 1024,  8,
> @@ -39,8 +72,9 @@ static const struct flash_info sst_parts[] = {
>  	{ "sst26vf016b", INFO(0xbf2641, 0, 64 * 1024, 32,
>  			      SECT_4K | SPI_NOR_DUAL_READ) },
>  	{ "sst26vf064b", INFO(0xbf2643, 0, 64 * 1024, 128,
> -			      SECT_4K | SPI_NOR_DUAL_READ |
> -			      SPI_NOR_QUAD_READ) },
> +			      SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
> +			      SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
> +		.fixups = &sst26vf_fixups },
>  };
> 
>  static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,