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SubjectRe: [PATCH v2] mtd: spi-nor: Return error when nor->addr_width does not match the device size
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Hi,

On 13/03/19 7:15 PM, Liu Xiang wrote:
> In some is25lp256, the DWORD1 of JEDEC Basic Flash Parameter Header
> is 0xfff920e5. So the DWORD1[18:17] Address Bytes bits are 0b00,
> means that 3-Byte only addressing. But the device size is larger
> than 16MB, nor->addr_width must be 4 to access the whole address.
> An error should be returned when nor->addr_width does not match
> the device size in spi_nor_parse_bfpt(). Then it can go back to
> use spi_nor_ids[] for setting the right addr_width.
>
> Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
> Signed-off-by: Liu Xiang <liu.xiang6@zte.com.cn>
> ---
> drivers/mtd/spi-nor/spi-nor.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 6e13bbd..63933c7 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -2811,6 +2811,14 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
> }
> params->size >>= 3; /* Convert to bytes. */
>
> + /*
> + * If the device exceeds 16MiB, addr_width must be 4.
> + * addr_width == 3 means the Address Bytes we are
> + * reading from BFPT is wrong.
> + */

JESD216 standard does not mandate flash devices >16MiB to always support
4 byte addressing opcode. So, its okay for flash vendor to support
>16MiB flash with 3 byte addressing and Bank/extended address register.

> + if (params->size > 0x1000000 && nor->addr_width == 3)
> + return -EINVAL;
> +

Assuming only DWORD1[18:17] bits are wrong, then returning from here
would mean we miss parsing Sector Erase settings, Quad Enable
Requirements etc from BFPT which is kind of bad.
I suggest to move the fix to[1], addr_width indicated in flash_info
struct of the device can take precedence over SFDP.

[1]https://elixir.bootlin.com/linux/latest/source/drivers/mtd/spi-nor/spi-nor.c#L4106


> /* Fast Read settings. */
> for (i = 0; i < ARRAY_SIZE(sfdp_bfpt_reads); i++) {
> const struct sfdp_bfpt_read *rd = &sfdp_bfpt_reads[i];
>

--
Regards
Vignesh

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