mainboard/google/coral: power off EN_PP3300_DX_LTE_SOC when entering S5

On Astronaunt, after the system enters the S5 power state, there is a
10-second timeout before the system transitions the power state from S5
to G3. The EN_PP3300_DX_LTE_SOC signal, which is controlled by GPIO_78
on the APL platform, remains on during that period. If the system is
powered back on before going to G3, the built-in modem won't go through
a power cycle as EN_PP3300_DX_LTE_SOC is never de-asserted.

Keeping the modem, and indirectly the SIM, powered during a quick system
power cycle may sometimes be undesirable. For instance, we would like a
SIM with PIN lock enabled to require unlocking each time the system is
powered on. After the SIM receives a PIN, it may remain unlocked until
its next power cycle.

Also, it is often desirable to power cycle the modem when the system
goes through a power cycle. For instance, a user may power cycle the
system to recover a wedged modem.

BUG=b:68365029
TEST=Tested the following on an Astronaunt device:
1. Verify that the modem is powered on after the system boots from cold.
2. Suspend the system to S0ix. Verify that the modem remains powered on
   when the system is in S0ix. After the system goes back to S0, verify
   that the SIM with PIN lock enabled doesn't request unlocking, and the
   modem can quickly reconnect to a network.
3. Configure the system to suspend to S3 instead of S0ix, and then
   repeat (2).
4. Perform a quick system power cycle, verify that the modem is powered
   cycle and the SIM with PIN lock enabled requests unlocking.

Change-Id: Ie60776d5d9ebc6a69aa9e360bd882f455265dfa2
Signed-off-by: Ben Chan <benchan@chromium.org>
Reviewed-on: https://review.coreboot.org/22415
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

0 files changed, 0 insertions, 0 deletions