Re: [PATCH] mtd: spi-nor: use 4 bit locking for MX25L12805D

[David Bauer <mail@david-bauer.net>]

Hi,

thanks for your review.

On 4/20/21 10:44 AM, Michael Walle wrote:
> Hi David,
> 
> Am 2021-04-16 18:28, schrieb David Bauer:
>> Macronix MX25L12805D supports locking with 4 block
>> protection bits in its status register. Add the corresponding
>> flag in order to clear these bits when unloking the flash.
>>
>> Otherwise, the flash might not be writable depending on the state
>> left by the bootloader.
>>
>> Tested-on: Ubiquiti UniFi AC Lite (ath79)
>>
>> Fixes commit 62593cf40b23 ("mtd: spi-nor: refactor block protection functions")
> 
> Strictly speaking, this is not a fix, because there was never
> locking support for macronix flashes.

You're right. On a second read, the description is a bit off, part of the reason
being the patch was part of another series from me some moths ago. I'll fix that.

> 
> This should also be in the subject, it should rather be "enable locking
> support" or something similar.
> 
> Btw. these bits are non-volatile, so if your bootloader will set
> them again, depending on the flash and your reboot cycles, they might
> wear out.

I didn't knew that, thanks for this information. Sadly this is the quirk of
the bootloader from Ubiquiti. Some versions of their UniFi and all of their
AirMax series behave like that.

Best
David

> 
>> Signed-off-by: David Bauer <mail@david-bauer.net>
> 
> With that:
> Reviewed-by: Michael Walle <michael@walle.cc>
> 
> -michael
> 
>> ---
>>  drivers/mtd/spi-nor/macronix.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/spi-nor/macronix.c b/drivers/mtd/spi-nor/macronix.c
>> index 2d39dd32a64e..ed8b56a0102f 100644
>> --- a/drivers/mtd/spi-nor/macronix.c
>> +++ b/drivers/mtd/spi-nor/macronix.c
>> @@ -50,7 +50,8 @@ static const struct flash_info macronix_parts[] = {
>>      { "mx25u4035",   INFO(0xc22533, 0, 64 * 1024,   8, SECT_4K) },
>>      { "mx25u8035",   INFO(0xc22534, 0, 64 * 1024,  16, SECT_4K) },
>>      { "mx25u6435f",  INFO(0xc22537, 0, 64 * 1024, 128, SECT_4K) },
>> -    { "mx25l12805d", INFO(0xc22018, 0, 64 * 1024, 256, SECT_4K) },
>> +    { "mx25l12805d", INFO(0xc22018, 0, 64 * 1024, 256, SECT_4K |
>> +                  SPI_NOR_HAS_LOCK | SPI_NOR_4BIT_BP) },
>>      { "mx25l12855e", INFO(0xc22618, 0, 64 * 1024, 256, 0) },
>>      { "mx25r1635f",  INFO(0xc22815, 0, 64 * 1024,  32,
>>                    SECT_4K | SPI_NOR_DUAL_READ |

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