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If CONFIG_WATCHDOG_HELP is defined, a 16-bit timer is used as an auxiliary timer to interrupt us 50ms before the watchdog expires. When the auxiliary timer expires, the stack trace is printed. Watchdog then expires 50ms after and reboots the system. BUG=chrome-os-partner:24107 TEST=Define CONFIG_WATCHDOG_HELP, and see stack trace on 'waitms 2000'. TEST=Undefine CONFIG_WATCHDOG_HELP, and check watchdog still works without printing stack trace. BRANCH=None Change-Id: I2555d3f86a15c83bb03a00c6807f77d9dddaf333 Signed-off-by: Vic (Chun-Ju) Yang <victoryang@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/178284 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.