[OpenWrt-Devel] lantiq: SPI cleanups and update to the new SPI driver

Martin Blumenstingl martin.blumenstingl at googlemail.com
Sun Jan 17 07:30:05 EST 2016

While upgrading the lantiq target to linux 4.4 it was discovered that the
SPI driver is not working with 4.4 anymore. Fixing it also does not seem
to be trivial.
However, Daniel Schwierzeck (thanks!) has provided a rewritten SPI driver.
His version works fine on 4.1 and 4.5, is now independant of spi-bitbang
and uses the same chip-select numbering as described in the datasheets.

While updating to this version there are some related clean-ups:
- our device .dts files are now initializing SPI correctly, regardless
  of the state in which the bootloader leaves the SPI pins
- all devices are now using the hardware SPI driver (FRITZ3370 and
  DGN3500/DGN3500B were still using spi-gpio)
- SPI can be re-enabled on EASY80920 since the SPI driver actually works
- Due to pinctrl changes (see patch 01 - 03) the hardcoded PCIe reset
  GPIO did not work anymore - thus we are now passing it via device-tree

I have successfully tested this changeset on two devices:
- TD-W8970 which uses SPI flash
- an ARX100 based board with NOR flash (to ensure that the pinctrl changes
  did not break other boards)
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