Re: [PATCH v2] mtd: spi-nor: macronix: enable 4-bit BP support for MX25L6405D

[Michael Walle <michael@walle.cc>]

Am 2021-01-23 13:18, schrieb Tudor.Ambarus@microchip.com:
> Hi, Sieng,
> 
> On 12/8/20 3:57 AM, Sieng Piaw Liew wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know 
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>> 
>> Enable 4-bit Block Protect support for MX256405D and its variants 
>> using
>> the same ID.
>> 
>> Tested on Innacom W3400V6 router with MX25L6406E chip.

MX25L6406E?

>> https://github.com/openwrt/openwrt/pull/3501
>> 
>> Signed-off-by: Sieng Piaw Liew <liew.s.piaw@gmail.com>
>> ---
>> Changes in v2:
>> - Add SPI_NOR_HAS_LOCK which SPI_NOR_4BIT_BP required.
>> 
>>  drivers/mtd/spi-nor/macronix.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/mtd/spi-nor/macronix.c 
>> b/drivers/mtd/spi-nor/macronix.c
>> index 9203abaac229..033ede381673 100644
>> --- a/drivers/mtd/spi-nor/macronix.c
>> +++ b/drivers/mtd/spi-nor/macronix.c
>> @@ -42,7 +42,9 @@ static const struct flash_info macronix_parts[] = {
>>         { "mx25l1606e",  INFO(0xc22015, 0, 64 * 1024,  32, SECT_4K) },
>>         { "mx25l3205d",  INFO(0xc22016, 0, 64 * 1024,  64, SECT_4K) },
>>         { "mx25l3255e",  INFO(0xc29e16, 0, 64 * 1024,  64, SECT_4K) },
>> -       { "mx25l6405d",  INFO(0xc22017, 0, 64 * 1024, 128, SECT_4K) },
>> +       { "mx25l6405d",  INFO(0xc22017, 0, 64 * 1024, 128,
>> +                             SECT_4K | SPI_NOR_HAS_LOCK |
>> +                             SPI_NOR_4BIT_BP) },
> 
> I've read again the datasheet[1], and to me it looks like we
> don't support the locking scheme for this flash.
> What mx25l6405d calls BP3, we refer to as Top/Bottom support (TB bit).
> The problem that I see is that mx25l6405d uses some kind of twisted
> TB bit.
> 
> For example, for BP3=1, BP2=0, BP1=0, BP0=1, the flash's datasheet
> states that the lower half blocks are protected (0th-63th), while in
> our code we would expect that just the lower first two blocks to be
> protected (0th and 1st). We need new support for this flash.

I double checked that and we don't support this. BP3 is indeed some
kind of TB bit. But not the TB bit which is currently supported. I
guess with the current code, protection scheme can be supported iff
BP3 == 0.

-michael

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