[][drivers: spi: add support for dynamic calibration]

Add support for dynamic calibration:
Provide a calibration template for all SPI devices, including SPI-flash.
We just need to implement (*cal_read) in your SPI drivers, and then we
can use this calibration flow.

SPI signal path is usually affected by many aspects, like flash socket
mounted or longer signal line length. So we need dynamic calibration
for SPI controllers and devices before we start using SPI devices.


Change-Id: I94313f3d186d425e8d73218d582cd9489af917c5
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6151750
1 file changed