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mtd: spi-nor: Add generic formula for SR block protection handling
The current mainline locking was restricted and could only be applied
to flashes that have 3 block protection bits and fixed locking ratio.
A new method of normalization was reached at the end of the discussion [1].
(1) - if bp slot is insufficient.
(2) - if bp slot is sufficient.
if (bp_slots_needed > bp_slots) // (1)
min_prot_length = sector_size << (bp_slots_needed - bp_slots);
else // (2)
min_prot_length = sector_size;
This patch changes logic to handle block protection based on min_prot_length.
It is suitable for the overall flashes with exception of some corner cases
(see EON and catalyst) and easy to extend and apply for the case of 2bit or
4bit block protection.
[1] http://lists.infradead.org/pipermail/linux-mtd/2020-February/093934.html
Signed-off-by: Jungseung Lee <js07.lee@samsung.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>