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This fixes a rare problem in which the EC could shutdown due to a false over-temperature when entering S0 on Haswell architectures. The fix involves requiring two valid reads of the temperature sensor (out of the last 4 readings) in order to report it. BUG=chrome-os-partner:24204 BRANCH=none TEST=See bug report for a patch that recreates the bug at a significantly higher rate then it would occur on its own. Using that patch, I implemented this fix, and made sure that there were no false over-temperatures reported. Change-Id: I0454eca1b96fd2fa1833b080026ed8f1caeeddc4 Signed-off-by: Alec Berg <alecaberg@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/177963 Reviewed-by: Randall Spangler <rspangler@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.