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Diffstat (limited to 'Documentation/mtd/spi-nor.txt')
| -rw-r--r-- | Documentation/mtd/spi-nor.txt | 65 |
1 files changed, 0 insertions, 65 deletions
diff --git a/Documentation/mtd/spi-nor.txt b/Documentation/mtd/spi-nor.txt deleted file mode 100644 index da1fbff5a24c..000000000000 --- a/Documentation/mtd/spi-nor.txt +++ /dev/null @@ -1,65 +0,0 @@ - SPI NOR framework - ============================================ - -Part I - Why do we need this framework? ---------------------------------------- - -SPI bus controllers (drivers/spi/) only deal with streams of bytes; the bus -controller operates agnostic of the specific device attached. However, some -controllers (such as Freescale's QuadSPI controller) cannot easily handle -arbitrary streams of bytes, but rather are designed specifically for SPI NOR. - -In particular, Freescale's QuadSPI controller must know the NOR commands to -find the right LUT sequence. Unfortunately, the SPI subsystem has no notion of -opcodes, addresses, or data payloads; a SPI controller simply knows to send or -receive bytes (Tx and Rx). Therefore, we must define a new layering scheme under -which the controller driver is aware of the opcodes, addressing, and other -details of the SPI NOR protocol. - -Part II - How does the framework work? --------------------------------------- - -This framework just adds a new layer between the MTD and the SPI bus driver. -With this new layer, the SPI NOR controller driver does not depend on the -m25p80 code anymore. - - Before this framework, the layer is like: - - MTD - ------------------------ - m25p80 - ------------------------ - SPI bus driver - ------------------------ - SPI NOR chip - - After this framework, the layer is like: - MTD - ------------------------ - SPI NOR framework - ------------------------ - m25p80 - ------------------------ - SPI bus driver - ------------------------ - SPI NOR chip - - With the SPI NOR controller driver (Freescale QuadSPI), it looks like: - MTD - ------------------------ - SPI NOR framework - ------------------------ - fsl-quadSPI - ------------------------ - SPI NOR chip - -Part III - How can drivers use the framework? ---------------------------------------------- - -The main API is spi_nor_scan(). Before you call the hook, a driver should -initialize the necessary fields for spi_nor{}. Please see -drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to fsl-quadspi.c -when you want to write a new driver for a SPI NOR controller. -Another API is spi_nor_restore(), this is used to restore the status of SPI -flash chip such as addressing mode. Call it whenever detach the driver from -device or reboot the system. |