charge_state_v2: Add explicit check for battery disconnect state

The charge_prevent_power_on() function checks for battery presence and
its charge level as a condition to prevent AP power on. In order to
deal with the short (up to a few seconds) time window where the fuel
gauge can be read but the discharge FET is not yet enabled, the
status of battery_get_disconnect_state() has been added as a condition
to many board's battery_is_present() function.

The problem with this approach is that the return value of
battery_is_present() is also used by charge_state_v2 as a condition to
force the charge state to ST_IDLE. Then, if the config option
CONFIG_CHARGER_MAINTAIN_VBAT is not defined, the value of requested
current and voltage will be forced to 0 as long as the state remains
in ST_IDLE. When the battery is dead or has been cutoff its discharge
FET will be disabled. In order to for the discharge FET to be enabled
the charger must provide at least a precharge level of current to the
battery. But, if the FET status is used as a condition for
battery_is_present which in turn forces the charge state to ST_IDLE
which can lead to requested_current being forced to 0.

This CL enables a way to remove battery_get_disconnect_state() as a
condition from battery_is_present and instead call
battery_get_disconnect_state() directly in the function
charge_prevent_power_on. Therefore AP power can still be gated by the
battery FET status, but the charge state will not be stuck in ST_IDLE.

This new check is guarded by CONFIG_BATTERY_REVIVE_DISCONNECT. Boards
which currently condition battery_is_present on the value of
battery_get_disconnect_state() don't change at all, but a board which
needs to remove that condition on battery_is_present can still use the
FET check to prevent AP power on.

BUG=b:79133101
BRANCH=none
TEST=Tested on Yorp and verifed that when using either a dead battery
or a battery that had been cutoff, prevent_power_on was set to 1 until
the FET status was correct for the battery to provide power.

Change-Id: Ic27f42610a7b751394b29a013c4dd17030a3df31
Signed-off-by: Scott Collyer <scollyer@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1053095
Commit-Ready: Scott Collyer <scollyer@chromium.org>
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/common/charge_state_v2.c b/common/charge_state_v2.c
index f5da9b8873..d0f5d30512 100644
--- a/common/charge_state_v2.c
+++ b/common/charge_state_v2.c
@@ -1866,8 +1866,14 @@ int charge_prevent_power_on(int power_button_pressed)
 		current_batt_params = &params;
 	}
 
-	/* Require a minimum battery level to power on */
+	/*
+	 * Require a minimum battery level to power on and ensure that the
+	 * battery can prvoide power to the system.
+	 */
 	if (current_batt_params->is_present != BP_YES ||
+#ifdef CONFIG_BATTERY_REVIVE_DISCONNECT
+	    battery_get_disconnect_state() != BATTERY_NOT_DISCONNECTED ||
+#endif
 	    current_batt_params->state_of_charge <
 	    CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON)
 		prevent_power_on = 1;