pd: Limit input current to 500mA on PD voltage transition

Upon requesting a PD power contract at a new voltage, keep the input
current limit at 500mA until PD_RDY is received.

BUG=b:30744563,chrome-os-partner:59311,chrome-os-partner:44340
BRANCH=ryu, gru, glados
TEST=Manual on kevin, set ilim to 5V through `chglim` console command,
attach zinger. Set ilim to 20V through `chglim`, verify that ilim goes
from 3A to 500mA to 3A.

Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Change-Id: I452f183cfb958780e336a9f99dc6398356de17a0
Reviewed-on: https://chromium-review.googlesource.com/399918
Commit-Ready: Shawn N <shawnn@chromium.org>
Tested-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/430245
(cherry picked from commit 92b3623dad47f47e06168bc5f4a04417254b7028)
Reviewed-on: https://chromium-review.googlesource.com/430632
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>

4 files changed, 46 insertions, 3 deletions

diff --git a/common/charge_manager.c b/common/charge_manager.c
index 673a85ab6f..b055c5d28d 100644
--- a/common/charge_manager.c
+++ b/common/charge_manager.c
@@ -720,6 +720,24 @@ void charge_manager_set_ceil(int port, enum ceil_requestor requestor, int ceil)
 	}
 }
 
+void charge_manager_force_ceil(int port, int ceil)
+{
+	ASSERT(port >= 0 && port < CONFIG_USB_PD_PORT_COUNT);
+
+	/*
+	 * Force our input current to ceil if we're exceeding it, without
+	 * waiting for our deferred task to run.
+	 */
+	if (port == charge_port && ceil < charge_current)
+		board_set_charge_limit(ceil, CHARGE_SUPPLIER_PD);
+
+	/*
+	 * Now inform charge_manager so it stays in sync with the state of
+	 * the world.
+	 */
+	charge_manager_set_ceil(port, CEIL_REQUESTOR_PD, ceil);
+}
+
 /**
  * Select an 'override port', a port which is always the preferred charge port.
  * Returns EC_SUCCESS on success, ec_error_list status on failure.
diff --git a/common/usb_pd_protocol.c b/common/usb_pd_protocol.c
index 4c4ad4b40d..d3b1c4972a 100644
--- a/common/usb_pd_protocol.c
+++ b/common/usb_pd_protocol.c
@@ -606,9 +606,16 @@ static void pd_send_request_msg(int port, int always_send_request)
 		 */
 		return;
 
-	/* Don't re-request the same voltage */
-	if (!always_send_request && pd[port].prev_request_mv == supply_voltage)
-		return;
+	if (!always_send_request) {
+		/* Don't re-request the same voltage */
+		if (pd[port].prev_request_mv == supply_voltage)
+			return;
+#ifdef CONFIG_CHARGE_MANAGER
+		/* Limit current to PD_MIN_MA during transition */
+		else
+			charge_manager_force_ceil(port, PD_MIN_MA);
+#endif
+	}
 
 	CPRINTF("Req C%d [%d] %dmV %dmA", port, RDO_POS(rdo),
 		supply_voltage, curr_limit);
diff --git a/include/charge_manager.h b/include/charge_manager.h
index faca0104eb..a88cbe6e06 100644
--- a/include/charge_manager.h
+++ b/include/charge_manager.h
@@ -54,6 +54,16 @@ enum ceil_requestor {
 /* Update charge ceiling for a given port / requestor */
 void charge_manager_set_ceil(int port, enum ceil_requestor requestor, int ceil);
 
+/*
+ * Update PD charge ceiling for a given port. In the event that our ceiling
+ * is currently above ceil, change the current limit before returning, without
+ * waiting for a charge manager refresh. This function should only be used in
+ * time-critical situations where we absolutely cannot proceed without limiting
+ * our input current, and it should only be called from the PD tasks.
+ * If you ever call this function then you are a terrible person.
+ */
+void charge_manager_force_ceil(int port, int ceil);
+
 /* Select an 'override port', which is always the preferred charge port */
 int charge_manager_set_override(int port);
 int charge_manager_get_override(void);
diff --git a/test/charge_manager.c b/test/charge_manager.c
index 98871cd1b5..8bbfcf11ea 100644
--- a/test/charge_manager.c
+++ b/test/charge_manager.c
@@ -293,6 +293,14 @@ static int test_charge_ceil(void)
 	TEST_ASSERT(active_charge_port == 1);
 	TEST_ASSERT(active_charge_limit == 2500);
 
+	/* Verify forced ceil takes effect immediately */
+	charge_manager_force_ceil(1, 500);
+	TEST_ASSERT(active_charge_port == 1);
+	TEST_ASSERT(active_charge_limit == 500);
+	wait_for_charge_manager_refresh();
+	TEST_ASSERT(active_charge_port == 1);
+	TEST_ASSERT(active_charge_limit == 500);
+
 	return EC_SUCCESS;
 }