[RFC PATCH v2 0/2] Add support to Disable the flash quad mode

[Yicong Yang <yangyicong@xxxxxxxxxxxxx>]

Previously we didn't disable the flash's quad mode when it's removed
Then comes the problem that if we next time load the flash
in SPI/Dual mode, it will not be correctly enabled as the quad enable
bits has not been cleared. I validated the condition on Cypress s25fs128s1.

This series adds the capability to disable the flash's quad mode. And
restore the flash when it's removed in spi_nor_restore().

RFC:
- I cleared quad mode bit in spi_nor_restore() when flash removed or
shutdown, follow what reset 4byte address does. But I don't know if
there is a situation that the flash is in quad mode by default. If so,
we should disable it in probe stage.
- The issue occurs when the user switch the spi mode of the flash.
Not sure whether a situation exists.

Changes since v1:
- modify the comments and fix the condition suggested by Pratyush's.
Link: https://lore.kernel.org/linux-mtd/1587720044-49172-1-git-send-email-yangyicong@xxxxxxxxxxxxx/

Yicong Yang (2):
  mtd: spi-nor: Add capability to disable flash quad mode
  mtd: spi-nor: Disable the flash quad mode in spi_nor_restore()

 drivers/mtd/spi-nor/core.c | 56 +++++++++++++++++++++++++++++++++-------------
 drivers/mtd/spi-nor/core.h |  8 +++----
 2 files changed, 44 insertions(+), 20 deletions(-)

-- 
2.8.1


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