ocpc: Miscellaneous fixes

This commit just performs some miscellaneous fixes for OCPC.

Some key fixes are:
 - Fix handling of full batteries with respect to CFET status
 - Reducing upward transitions
 - Restrict system resistance calculations to high current scenarios
   only.

BUG=b:168135339
BRANCH=None
TEST=Build and flash waddldee with new PID constants, drain battery,
verify DUT can charge from the sub board port all the way to full,
verify DUT can source out the main board port while charging from the
sub board.  Verify that the charging curve is fairly stable.

Signed-off-by: Aseda Aboagye <aaboagye@google.com>
Change-Id: Id170b1c5dfe56733f4ebcf350bf96d0de59e3ec4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2411467
Tested-by: Aseda Aboagye <aaboagye@chromium.org>
Commit-Queue: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Diana Z <dzigterman@chromium.org>

1 files changed, 23 insertions, 13 deletions

diff --git a/common/ocpc.c b/common/ocpc.c
index 39718cb923..42963751e3 100644
--- a/common/ocpc.c
+++ b/common/ocpc.c
@@ -70,7 +70,11 @@ enum ec_error_list ocpc_calc_resistances(struct ocpc_data *ocpc,
 {
 	int act_chg = ocpc->active_chg_chip;
 
-	if ((battery->current <= 0) ||
+	/*
+	 * In order to actually calculate the resistance, we need to make sure
+	 * we're actually charging the battery at a significant rate.
+	 */
+	if ((battery->current <= 1000) ||
 	    (!(ocpc->chg_flags[act_chg] & OCPC_NO_ISYS_MEAS_CAP) &&
 	     (ocpc->isys_ma <= 0)) ||
 	    (ocpc->vsys_aux_mv < ocpc->vsys_mv)) {
@@ -115,7 +119,7 @@ int ocpc_config_secondary_charger(int *desired_input_current,
 	struct charger_params charger;
 	int vsys_target = 0;
 	int drive = 0;
-	int i_ma;
+	int i_ma = 0;
 	int min_vsys_target;
 	int error = 0;
 	int derivative = 0;
@@ -138,13 +142,18 @@ int ocpc_config_secondary_charger(int *desired_input_current,
 	if (chgnum != CHARGER_SECONDARY)
 		return EC_ERROR_INVAL;
 
+	if (current_ma == 0) {
+		vsys_target = voltage_mv;
+		goto set_vsys;
+	}
+
 	/*
 	 * Check to see if the charge FET is disabled.  If it's disabled, the
 	 * charging loop is broken and increasing VSYS will not actually help.
 	 * Therefore, don't make any changes at this time.
 	 */
 	if (battery_is_charge_fet_disabled()) {
-		/* Only print this if there's actually a  CFET present. */
+		/* Only print this if there's actually a CFET present. */
 		if (battery_is_present())
 			CPRINTS("CFET disabled; not changing VSYS!");
 
@@ -189,10 +198,6 @@ int ocpc_config_secondary_charger(int *desired_input_current,
 		iterations = 0;
 	}
 
-	if (current_ma == 0) {
-		vsys_target = voltage_mv;
-		goto set_vsys;
-	}
 
 	/*
 	 * We need to induce a current flow that matches the requested current
@@ -261,6 +266,10 @@ int ocpc_config_secondary_charger(int *desired_input_current,
 		if (ABS(error) < i_step)
 			error = 0;
 
+		/* Make a note if we're significantly over target. */
+		if (error < -100)
+			CPRINTS("OCPC: over target %dmA", error * -1);
+
 		derivative = error - ocpc->last_error;
 		ocpc->last_error = error;
 		ocpc->integral +=  error;
@@ -287,12 +296,12 @@ int ocpc_config_secondary_charger(int *desired_input_current,
 			(k_i * ocpc->integral / k_i_div) +
 			(k_d * derivative / k_d_div);
 		/*
-		 * Let's limit upward transitions to 500mV.  It's okay to reduce
+		 * Let's limit upward transitions to 200mV.  It's okay to reduce
 		 * VSYS rather quickly, but we'll be conservative on
 		 * increasing VSYS.
 		 */
-		if (drive > 500)
-			drive = 500;
+		if (drive > 200)
+			drive = 200;
 		CPRINTS_DBG("drive = %d", drive);
 	}
 
@@ -312,11 +321,12 @@ int ocpc_config_secondary_charger(int *desired_input_current,
 		vsys_target = batt.desired_voltage;
 
 	/*
-	 * Ensure VSYS is no higher than 1V over the max battery voltage, but
-	 * greater than or equal to our minimum VSYS target.
+	 * Ensure VSYS is no higher than the specified maximum battery voltage
+	 * plus the voltage drop across the system.
 	 */
 	vsys_target = CLAMP(vsys_target, min_vsys_target,
-			    batt_info->voltage_max+1000);
+			    batt_info->voltage_max +
+			    (i_ma * ocpc->combined_rsys_rbatt_mo / 1000));
 
 	/* If we're input current limited, we cannot increase VSYS any more. */
 	CPRINTS_DBG("OCPC: Inst. Input Current: %dmA (Limit: %dmA)",