tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
fork atom

docs: mtd: spi-nor: drop obsolete info

The architecture description is obsolete, it no longer applies to
the current SPI NOR framework state, remove it.

Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Link: https://lore.kernel.org/r/20231124184902.1194235-3-tudor.ambarus@linaro.org
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

Tudor Ambarus 9b3eae34 bb1f9e39

-62
-62
Documentation/driver-api/mtd/spi-nor.rst
··· 2 2 SPI NOR framework 3 3 ================= 4 4 5 - Part I - Why do we need this framework? 6 - --------------------------------------- 7 - 8 - SPI bus controllers (drivers/spi/) only deal with streams of bytes; the bus 9 - controller operates agnostic of the specific device attached. However, some 10 - controllers (such as Freescale's QuadSPI controller) cannot easily handle 11 - arbitrary streams of bytes, but rather are designed specifically for SPI NOR. 12 - 13 - In particular, Freescale's QuadSPI controller must know the NOR commands to 14 - find the right LUT sequence. Unfortunately, the SPI subsystem has no notion of 15 - opcodes, addresses, or data payloads; a SPI controller simply knows to send or 16 - receive bytes (Tx and Rx). Therefore, we must define a new layering scheme under 17 - which the controller driver is aware of the opcodes, addressing, and other 18 - details of the SPI NOR protocol. 19 - 20 - Part II - How does the framework work? 21 - -------------------------------------- 22 - 23 - This framework just adds a new layer between the MTD and the SPI bus driver. 24 - With this new layer, the SPI NOR controller driver does not depend on the 25 - m25p80 code anymore. 26 - 27 - Before this framework, the layer is like:: 28 - 29 - MTD 30 - ------------------------ 31 - m25p80 32 - ------------------------ 33 - SPI bus driver 34 - ------------------------ 35 - SPI NOR chip 36 - 37 - After this framework, the layer is like:: 38 - 39 - MTD 40 - ------------------------ 41 - SPI NOR framework 42 - ------------------------ 43 - m25p80 44 - ------------------------ 45 - SPI bus driver 46 - ------------------------ 47 - SPI NOR chip 48 - 49 - With the SPI NOR controller driver (Freescale QuadSPI), it looks like:: 50 - 51 - MTD 52 - ------------------------ 53 - SPI NOR framework 54 - ------------------------ 55 - fsl-quadSPI 56 - ------------------------ 57 - SPI NOR chip 58 - 59 - Part III - How can drivers use the framework? 60 - --------------------------------------------- 61 - 62 - The main API is spi_nor_scan(). Before you call the hook, a driver should 63 - initialize the necessary fields for spi_nor{}. Please see 64 - drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to spi-fsl-qspi.c 65 - when you want to write a new driver for a SPI NOR controller. 66 - 67 5 How to propose a new flash addition 68 6 ----------------------------------- 69 7