cr50: use interrupts for ap_state

The ap_state machine as is is pretty hard to modify as it's implemented
now. The state machine has to have certain states set at certain points
to handle AP detection properly and it is very slow to detect AP off. It
takes a second and it will only detect AP off if TPM_RST_L stays
asserted for 1 second. This change modifies ap_state.c to use interrupts
instead of polling, so it can detect when the AP is off immediately and
wont miss any resets. This is required for the new closed loop reset
feature. Cr50 has to be able to detect all AP resets and it can't take 1
second for cr50 to determine the AP is off.

We used polling because we had to use APTX_CR50RX to detect AP state for
a while. The UART level changes a lot. Processing all of the interrupts
really impacted CCD uart, so we couldn't use interrupts to detect the
state. We had to poll. AP UART isn't used to detect AP state anymore on
any platforms, so it's ok to switch to interrupts now.

APTX_CR50RX is still used for ap uart detection in ap_uart_state.c. This
change doesn't modify that at all.

BUG=b:123544145
BRANCH=cr50
TEST=Make sure suspend and reboot stress tests still work on a bob and a
soraka. Check that Cr50 detects the AP state correctly.

Change-Id: I80eb97aecffe460b7857e66e7204a55b72c9dd47
Signed-off-by: Mary Ruthven <mruthven@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1446999
Commit-Ready: Mary Ruthven <mruthven@chromium.org>
Tested-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

0 files changed, 0 insertions, 0 deletions