mirror of
https://github.com/Telecominfraproject/OpenCellular.git
synced 2026-01-11 10:25:20 +00:00
7a9ba2bae9
A recent cr50 loader modification introduced a counter in a scratch
register which is incremented on every startup. The idea is that valid
RW would decrement the counter, signaling that the start was
successful.
Should the counter exceed the value of 5, the loader assumes that the
RW being started is not fit to run, and picks the older RW to run, if
available.
This patch adds a function to process the startup retry counter.
First of all the counter is zeroed, as this function is supposed to be
called only once the RW run is considered successful and reliable.
Then the current situation is examined. If the counter value read from
the scratch register exceeds 5 AND running image is not the newer of A
and B, it is considered an indication of a fallback from a bad newer
image.
To prevent the newer image from being considered a contender on the
following startups, its header is corrupted.
BRANCH=none
BUG=chrome-os-partner:55151, chrome-os-partner:55667
TEST=modified code for testing purposes, by adding a call to
system_process_retry_counter() to tpm_task() after line 534, which
would cause the new function to be called soon after boot.
built a new image and installed it on the debug board. Then
modified the image to throw an exception early in the boot up
sequence, and installed it as a newer image on the debug board.
Observed the debug board restart the new image several time and
then fall back to the older image, printing the following on the
console:
system_process_retry_counter:retry counter 7
corrupt_other_header: RW fallback must have happened, magic at 44000 before: ffffffff
corrupt_other_header: magic after: 0
The following restarts start the older image without trying to run
the failing newer image.
Change-Id: Ia7497401e38fe2c3957af910cf745e45da985245
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/362776
Reviewed-by: Randall Spangler <rspangler@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