DragonEgg: Enable/disable battery learn mode based on AC

This CL is a software workaround for an issue with the bq25710
charger. There is an issue with the converter control loop not being
biased correctly when it starts switching. This leads to a reverse
current (from battery to charger). To avoid this issue, the switching
converter is turned off when AC is not present, then only enalbed 200
msec after AC presence is detected.

BUG=b:112372451
BRANCH=none
TEST=Veried that reverse buck/boost not present with this CL and that
charger still functions as expected.

Change-Id: I4d3a975e3c0e24cdf7f13fdab69da32ccd70a428
Signed-off-by: Scott Collyer <scollyer@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1168597
Commit-Ready: Scott Collyer <scollyer@chromium.org>
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/board/dragonegg/board.c b/board/dragonegg/board.c
index 162f596b38..e1ba7f4336 100644
--- a/board/dragonegg/board.c
+++ b/board/dragonegg/board.c
@@ -6,6 +6,7 @@
 /* DragonEgg board-specific configuration */
 
 #include "common.h"
+#include "charger.h"
 #include "console.h"
 #include "driver/ppc/sn5s330.h"
 #include "extpower.h"
@@ -57,3 +58,45 @@ void board_overcurrent_event(int port)
 		cprints(CC_USBPD, "p%d: overcurrent!", port);
 	}
 }
+
+static void board_disable_learn_mode(void)
+{
+	/* Disable learn mode after checking to make sure AC is still present */
+	if (extpower_is_present())
+		charger_discharge_on_ac(0);
+}
+DECLARE_DEFERRED(board_disable_learn_mode);
+
+static void board_extpower(void)
+{
+	/*
+	 * For the bq25710 charger, we need the switching converter to remain
+	 * disabled until ~130 msec from when VBUS present to allow the
+	 * converter to be biased properly. Otherwise, there will be a reverse
+	 * buck/boost until the converter is biased. The recommendation is to
+	 * exit learn mode 200 msec after external charger is connected.
+	 *
+	 * TODO(b/112372451): When there are updated versions of the bq25710,
+	 * this set of changes can be removed.
+	 */
+	if (extpower_is_present()) {
+		hook_call_deferred(&board_disable_learn_mode_data, 200 * MSEC);
+	} else {
+		/* Enable charger learn mode */
+		charger_discharge_on_ac(1);
+		/* Cancel any pending call to disable learn mode */
+		hook_call_deferred(&board_disable_learn_mode_data, -1);
+	}
+}
+DECLARE_HOOK(HOOK_AC_CHANGE, board_extpower, HOOK_PRIO_DEFAULT);
+
+/* Initialize board. */
+static void board_init(void)
+{
+	/*
+	 * On EC reboot, need to always set battery learn mode to the correct
+	 * state based on presence of AC.
+	 */
+	board_extpower();
+}
+DECLARE_HOOK(HOOK_INIT, board_init, HOOK_PRIO_DEFAULT);