linux-kernel - [PATCH v2] power: supply: qcom_battmgr: Report battery capacity

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Message-ID: <20250528112328.1640743-2-korneld@google.com>
Date: Wed, 28 May 2025 11:23:29 +0000
From: "Kornel Dulęba" <korneld@...gle.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, Sebastian Reichel <sre@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	"Kornel Dulęba" <korneld@...gle.com>
Subject: [PATCH v2] power: supply: qcom_battmgr: Report battery capacity

Battery charge can be reported in several different ways. One of them is
is charge percentage referred to as POWER_SUPPLY_PROP_CAPACITY in the
power supply API. Currently the driver reports the capacity in this way
on SM8350, but not on the newer variants referred to as SC8280XP in the
driver. Although this is not a bug in itself, not reporting the
percentage can confuse some userspace consumers.
Mimic what is done in the ACPI driver (drivers/acpi/battery.c) and
calculate the percentage capacity by dividing the current charge value
by the full charge.

Signed-off-by: Kornel Dulęba <korneld@...gle.com>
---
v2: Change the logic to avoid u64 division, which is problematic on
    32bit platforms.

 drivers/power/supply/qcom_battmgr.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/power/supply/qcom_battmgr.c b/drivers/power/supply/qcom_battmgr.c
index fe27676fbc7c..33a70f3d72bc 100644
--- a/drivers/power/supply/qcom_battmgr.c
+++ b/drivers/power/supply/qcom_battmgr.c
@@ -577,6 +577,8 @@ static int qcom_battmgr_bat_get_property(struct power_supply *psy,
 		val->intval = battmgr->status.capacity;
 		break;
 	case POWER_SUPPLY_PROP_CAPACITY:
+		if (battmgr->status.percent == (unsigned int)-1)
+			return -ENODATA;
 		val->intval = battmgr->status.percent;
 		break;
 	case POWER_SUPPLY_PROP_TEMP:
@@ -617,6 +619,7 @@ static const enum power_supply_property sc8280xp_bat_props[] = {
 	POWER_SUPPLY_PROP_STATUS,
 	POWER_SUPPLY_PROP_PRESENT,
 	POWER_SUPPLY_PROP_TECHNOLOGY,
+	POWER_SUPPLY_PROP_CAPACITY,
 	POWER_SUPPLY_PROP_CYCLE_COUNT,
 	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
 	POWER_SUPPLY_PROP_VOLTAGE_NOW,
@@ -1063,6 +1066,26 @@ static void qcom_battmgr_sc8280xp_callback(struct qcom_battmgr *battmgr,
 		battmgr->ac.online = source == BATTMGR_CHARGING_SOURCE_AC;
 		battmgr->usb.online = source == BATTMGR_CHARGING_SOURCE_USB;
 		battmgr->wireless.online = source == BATTMGR_CHARGING_SOURCE_WIRELESS;
+		if (battmgr->info.last_full_capacity != 0) {
+			/*
+			 * 100 * battmgr->status.capacity can overflow a 32bit
+			 * unsigned integer. FW readings are in m{W/A}h, which
+			 * are multiplied by 1000 converting them to u{W/A}h,
+			 * the format the power_supply API expects.
+			 * To avoid overflow use the original value for dividend
+			 * and convert the divider back to m{W/A}h, which can be
+			 * done without any loss of precision.
+			 */
+			battmgr->status.percent =
+				(100 * le32_to_cpu(resp->status.capacity)) /
+				(battmgr->info.last_full_capacity / 1000);
+		} else {
+			/*
+			 * Let the sysfs handler know no data is available at
+			 * this time.
+			 */
+			battmgr->status.percent = (unsigned int)-1;
+		}
 		break;
 	case BATTMGR_BAT_DISCHARGE_TIME:
 		battmgr->status.discharge_time = le32_to_cpu(resp->time);
-- 
2.49.0.1164.gab81da1b16-goog