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b91e63b0f9
The old low-level SPI protocol provided no useful information to the host about whether it was ready to receive or not. It also could get stuck waiting to receive data without setting up receive DMA, if the host did two transactions back-to-back. Add a real state machine to the SPI module. Add a range of byte codes the EC can return outside of a response frame, to indicate its current state. If the AP receives one of these codes, it can abort the transaction since it now knows the EC is unable to determine when it can send a response frame. This change is backwards-compatible with current AP firmware and kernel drivers, since those only look for the framing byte and don't care what other bytes are received in the meantime. BUG=chrome-os-partner:20257 BRANCH=none TEST=crosec test; passes at 70us. Change-Id: Ia06109ead3fbc421848e01050f7baf753cbeb16c Signed-off-by: Randall Spangler <rspangler@chromium.org> Reviewed-on: https://gerrit.chromium.org/gerrit/64254 Reviewed-by: Bill Richardson <wfrichar@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.