[PATCH 1/2] power: supply: qcom_battmgr: fix CHARGE_FULL* on SM8350-class firmware

[Jan-Michael Brummer <jan.brummer@tabos.org>]

battmgr->unit is only ever assigned in the BATTMGR_BAT_INFO handler of
the SC8280XP callback. The SM8350-class firmware does not implement that
request - every property is fetched individually via
BATTMGR_BAT_PROPERTY_GET - so unit keeps its zero-initialised value,
QCOM_BATTMGR_UNIT_mWh.

POWER_SUPPLY_PROP_CHARGE_FULL and POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN
are guarded by 'if (unit != QCOM_BATTMGR_UNIT_mAh) return -ENODATA;',
hence both properties always fail on these platforms, even though the
values are requested from the firmware and stored in
info.last_full_capacity and info.design_capacity on every access:

  $ cat /sys/class/power_supply/qcom-battmgr-bat/charge_full
  cat: read error: No data available

Without a full charge value userspace cannot derive an absolute energy
level, so UPower reports a zero energy level and never computes a
time-to-empty/time-to-full estimate:

    energy:              0 Wh
    energy-full:         0 Wh
    energy-rate:         12.4713 W
    percentage:          59%

The firmware of this class reports charge domain values, so set the unit
statically when registering the SM8350/SM8550 power supplies. With this
patch the properties read back consistently on a Fairphone 5:

  charge_full         4116000
  charge_full_design  4260000
  capacity            85

Fixes: 29e8142b5623 ("power: supply: Introduce Qualcomm PMIC GLINK power supply")
Signed-off-by: Jan-Michael Brummer <jan.brummer@tabos.org>
---
 drivers/power/supply/qcom_battmgr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/power/supply/qcom_battmgr.c b/drivers/power/supply/qcom_battmgr.c
index 490137a..98a70e1 100644
--- a/drivers/power/supply/qcom_battmgr.c
+++ b/drivers/power/supply/qcom_battmgr.c
@@ -1690,6 +1690,14 @@ static int qcom_battmgr_probe(struct auxiliary_device *adev,
 			return dev_err_probe(dev, PTR_ERR(battmgr->wls_psy),
 					     "failed to register wireless charing power supply\n");
 	} else {
+		/*
+		 * The SM8350-class firmware has no BATTMGR_BAT_INFO request, so
+		 * @unit is never populated from the firmware. It reports charge
+		 * domain values, so set it statically here - otherwise the
+		 * CHARGE_* properties are rejected with -ENODATA.
+		 */
+		battmgr->unit = QCOM_BATTMGR_UNIT_mAh;
+
 		if (battmgr->variant == QCOM_BATTMGR_SM8550)
 			psy_desc = &sm8550_bat_psy_desc;
 		else