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With CONFIG_HOST_COMMAND_STATUS, the EC can respond to a command with EC_RES_IN_PROGRESS, indicating to the AP that it should poll for completion of the command with EC_CMD_GET_COMMS_STATUS. The kernel, however, only guarantees the atomicity of single commands. As a result, i2c passtrough or keyboard commands could be issued while the AP is polling for completion of a flashrom command. By disabling CONFIG_HOST_COMMAND_STATUS, we eliminate polling of the EC status by the AP so that there is no interleaving of commands. BUG=chrome-os-partner:20978 TEST=flashrom on Pit BRANCH=pit Original-Change-Id: I48b29a0dbbcc56fc55f72ca64b8aff51036740e3 Signed-off-by: Andrew Bresticker <abrestic@chromium.org> Reviewed-on: https://gerrit.chromium.org/gerrit/66703 Reviewed-by: Randall Spangler <rspangler@chromium.org> (cherry picked from commit 2db4fcfb267b938fcc35af2a0d2e374f99551743) Change-Id: Iac7c15ec337d618cd6d95439d4b922bf3ec43916 Reviewed-on: https://gerrit.chromium.org/gerrit/66828 Reviewed-by: Randall Spangler <rspangler@chromium.org> Tested-by: Andrew Bresticker <abrestic@chromium.org> Commit-Queue: Andrew Bresticker <abrestic@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.