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dt-bindings: mtd: jedec, spi-nor: Add DT property to avoid setting SRWD bit in status register

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If the WP# signal of the flash device is either not connected or is wrongly
tied to GND (that includes internal pull-downs), and the software sets the
status register write disable (SRWD) bit in the status register then the
status register permanently becomes read-only. To avoid this added a new
boolean DT property "no-wp". If this property is set in the DT then the
software avoids setting the SRWD during status register write operation.

Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20230630142233.63585-2-amit.kumar-mahapatra@amd.com
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
This commit is contained in:
Amit Kumar Mahapatra
2023-06-30 19:52:32 +05:30
committed by Tudor Ambarus
parent 06c2afb862
commit cfc2928cb2
1 changed files with 15 additions and 0 deletions
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15
Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
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@@ -70,6 +70,21 @@ properties:
be used on such systems, to denote the absence of a reliable reset
mechanism.
no-wp:
type: boolean
description:
The status register write disable (SRWD) bit in status register, combined
with the WP# signal, provides hardware data protection for the device. When
the SRWD bit is set to 1, and the WP# signal is either driven LOW or hard
strapped to LOW, the status register nonvolatile bits become read-only and
the WRITE STATUS REGISTER operation will not execute. The only way to exit
this hardware-protected mode is to drive WP# HIGH. If the WP# signal of the
flash device is not connected or is wrongly tied to GND (that includes internal
pull-downs) then status register permanently becomes read-only as the SRWD bit
cannot be reset. This boolean flag can be used on such systems to avoid setting
the SRWD bit while writing the status register. WP# signal hard strapped to GND
can be a valid use case.
reset-gpios:
description:
A GPIO line connected to the RESET (active low) signal of the device.