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This is so the 30 second wait when no battery is installed can be skipped. Since Bolt needs a complete AC+Battery disconnect when updating the BIOS this 30 second wait is aggravating. BUG=chrome-os-partner:20448 BRANCH=bolt TEST=disconnect AC+Battery, then connect AC and watch it boot without waiting for 30 seconds. Change-Id: Ibaf42fe1dba9c74aa465aa0a1a5381ba6981f66e Signed-off-by: Duncan Laurie <dlaurie@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/171689 Reviewed-by: Bill Richardson <wfrichar@chromium.org> Reviewed-by: Dave Parker <dparker@chromium.org> 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.