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Before this change drivers had no way of knowing that a frequency change was coming. This could cause problems for some drivers (like i2c) that need to make sure that a transaction isn't happening while a frequency change is happening. The PRE_FREQ_CHANGE archiecture is very simple here and we don't allow any way to cancel it. At the moment, we guarantee: - We won't call PRE_FREQ_CHANGE with interrupts disabled, so acquiring locks / sleeping is OK. - We'll call the actual HOOK_FREQ_CHANGE after the PRE_FREQ_CHANGE. PRE_FREQ_CHANGE and HOOK_FREQ_CHANGE should not use deferred function calls. BRANCH=pit BUG=chrome-os-partner:22093 TEST=With all patches together: - on AP: suspend_stress_test - on EC: battery 10000 50 Change-Id: I2731a3e85d41e749fa571fdb74b5c9b12043cda6 Signed-off-by: Doug Anderson <dianders@chromium.org> Previous-Reviewed-on: https://chromium-review.googlesource.com/167101 (cherry picked from commit d84c0dbbf7c5a72917a820e292ecfdfa698d0fb9) Reviewed-on: https://chromium-review.googlesource.com/167148 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.