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

["Liu Xiang" <liuxiang_1999@126.com>]

Hi, Vignesh






At 2019-03-19 13:22:15, "Vignesh Raghavendra" <vigneshr@ti.com> wrote:
>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

Boris has added a fixup function, do you think this is more better:

static int
is25lp256_post_bfpt_fixups(struct spi_nor *nor,
			    const struct sfdp_parameter_header *bfpt_header,
			    const struct sfdp_bfpt *bfpt,
			    struct spi_nor_flash_parameter *params)
{
	/*
	 * IS25LP256 supports 4B opcodes.
	 * Unfortunately, some devices get BFPT_DWORD1_ADDRESS_BYTES_3_ONLY  
	 * from BFPT table for address width. We should fix it.
	 */
	if (bfpt.dwords[BFPT_DWORD(1)] & BFPT_DWORD1_ADDRESS_BYTES_MASK == 
		BFPT_DWORD1_ADDRESS_BYTES_3_ONLY)
		nor->addr_width = 4;

	return 0;
}

static struct spi_nor_fixups is25lp256_fixups = {
	.post_bfpt = is25lp256_post_bfpt_fixups,
};


>
>
>>  	/* 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