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The STM32H7 family has 2 banks of flash (with 2 hardware controllers able to do 2 parallel operations at the same time). Each bank of flash has 4 or 8 128-kB erase blocks (1MB and 2MB variants). The flash can only be written by 256-bit word (with an additional 10-bit ECC computed by the hardware). For the flash write-protection, we cannot use our 'classical' PSTATE scheme as the erase-blocks are too large (128-kB) to dedicate one to this and the embedded word in the RO partition would not work as the flash has ECC and triggers bus-fault when the ECC is incorrect (which includes the case where the 256-bit word is written a second time). So we will do the following: - use the RSS1 bit in the option bytes as the Write-Protect enabled bit. - if the WP GPIO is set, lock at startup the option bytes until next reboot. Signed-off-by: Vincent Palatin <vpalatin@chromium.org> BRANCH=none BUG=b:67081508 TEST=run flashinfo/flashwp/flashwrite/flasherase commands on the EC console. Change-Id: I823fce3bd42b4df212cf0b8ceceaca84109b78e6 Reviewed-on: https://chromium-review.googlesource.com/901423 Commit-Ready: Vincent Palatin <vpalatin@chromium.org> Tested-by: Vincent Palatin <vpalatin@chromium.org> Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
For an overview of the Embedded Controller firmware, refer to http://www.chromium.org/chromium-os/2014-firmware-summit For instructions on building from source, refer to http://www.chromium.org/chromium-os/ec-development/getting-started-building-ec-images-quickly