ASPEED SoCs support dual-boot feature for SPI Flash. When strapped appropriately, the SoC starts wdt2 (/dev/watchdog1) and if within a minute it is not disabled, it goes off and reboots the SoC from an alternate SPI Flash chip by changing CS0 controls to actually drive CS1 line.
When booted from alternate chip, in order to access the main chip at CS0, the user must reset the appropriate bit in the watchdog hardware. There is no interface that would allow to do that from an embedded firmware startup script. This commit implements support for that feature: * Enable 'alt-boot' option for wdt2 * Enable secondary SPI flash chip * Make it possible to get access to the primary SPI flash chip at CS0 after booting from the alternate chip at CS1. A sysfs interface is added to provide an easy way for embedded firmware startup scripts to clear the chip select bit to gain access to the primary flash chip in order to allow for recovery of its contents. Ivan Mikhaylov (4): vesnin: add wdt2 section with alt-boot option vesnin: add secondary SPI flash chip watchdog/aspeed: add support for dual boot dt-bindings/watchdog: Add access_cs0 option for alt-boot .../bindings/watchdog/aspeed-wdt.txt | 7 +++ arch/arm/boot/dts/aspeed-bmc-opp-vesnin.dts | 12 ++++ drivers/watchdog/aspeed_wdt.c | 62 ++++++++++++++++++- 3 files changed, 80 insertions(+), 1 deletion(-) -- 2.20.1
