[RESEND PATCH 1/2] mtd: spi-nor: do not touch TB bit without SPI_NOR_HAS_TB

[Ivan Mikhaylov]

On Wed, 2020-09-30 at 15:06 +0530, Vignesh Raghavendra wrote:
> 
> On 9/21/20 4:54 PM, Ivan Mikhaylov wrote:
> > Some chips like macronix don't have TB(Top/Bottom protection)
> > bit in the status register. Do not write tb_mask inside status
> > register, unless SPI_NOR_HAS_TB is present for the chip.
> > 
> 
> Not entirely accurate.. Macronix chips have TB bit in config register
> and is OTP and hence should not be touched ideally...
> 
> You still need to "read" that bit to determine actual scheme (Top vs
> Bottom). This is needs to be done before 2/2 enables SPI_NOR_HAS_LOCK
> flag for macronix flashes.

Vignesh, that's the point about this commit to generalize this part about TB bit
plus there is already exist SPI_NOR_HAS_TB flag which representing state of TB
existence. I didn't add any support for macronix's TB bit, that's true but
that's enough to make macronix chips able to use lock mechanism with default
'use_top' or any other chips which doesn't have TB bit.

> I guess macronix does not support SR_SRWD right? This needs special
> treatment as well.

It does support SR_SRWD as well. No need any special treatment here.

Thanks.