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So far we can only reliably sense a watchdog reset, but this saving/checking reset cause will at least make 'ap-off' flag work. BUG=chrome-os-partner:24107 TEST='waitms 2000' and see reset cause = 'watchdog' TEST='reboot ap-off' and see reset cause includes 'ap-off' TEST='reboot preserve' and see previous reset cause is preserved. BRANCH=None Change-Id: Id47a72d615489c9d9cd0b8761cfa699f08c724df Signed-off-by: Vic (Chun-Ju) Yang <victoryang@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/178277 Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
In the most general case, the flash layout looks something like this: +---------------------+ | Reserved for EC use | +---------------------+ +---------------------+ | Vblock B | +---------------------+ | RW firmware B | +---------------------+ +---------------------+ | Vblock A | +---------------------+ | RW firmware A | +---------------------+ +---------------------+ | FMAP | +---------------------+ | Public root key | +---------------------+ | Read-only firmware | +---------------------+ BIOS firmware (and kernel) put the vblock info at the start of each image where it's easy to find. The Blizzard EC expects the firmware vector table to come first, so we have to put the vblock at the end. This means we have to know where to look for it, but that's built into the FMAP and the RO firmware anyway, so that's not an issue. The RO firmware doesn't need a vblock of course, but it does need some reserved space for vboot-related things. Using SHA256/RSA4096, the vblock is 2468 bytes (0x9a4), while the public root key is 1064 bytes (0x428) and the current FMAP is 644 bytes (0x284). If we reserve 4K at the top of each FW image, that should give us plenty of room for vboot-related stuff.