mtd: spi-nor: add support for DTR protocol

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Double Transfer Rate (DTR) is SPI protocol in which data is transferred
on each clock edge as opposed to on each clock cycle. Make
framework-level changes to allow supporting flashes in DTR mode.

Right now, mixed DTR modes are not supported. So, for example a mode
like 4S-4D-4D will not work. All phases need to be either DTR or STR.

The xSPI spec says that "The program commands provide SPI backward
compatible commands for programming data...". So 8D-8D-8D page program
opcodes are populated with using 1S-1S-1S opcodes.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201005153138.6437-4-p.yadav@ti.com

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This commit is contained in:

Pratyush Yadav 2020-10-05 21:01:26 +05:30 • committed by Vignesh Raghavendra

parent 6e1bf55d72

commit 0e30f47232

4 changed files with 290 additions and 96 deletions

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319

drivers/mtd/spi-nor/core.c

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7

drivers/mtd/spi-nor/core.h

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9

drivers/mtd/spi-nor/sfdp.c

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51

include/linux/mtd/spi-nor.h

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