[PATCH 1/1] power: supply: max17042_battery: use VFSOC for capacity when no rsns

Henrik Grimler
2021-09-19T20:15:02Z

On Galaxy S3 (i9300/i9305), which has the max17047 fuel gauge and no
current sense resistor (rsns), the RepSOC register does not provide an
accurate state of charge value. The reported value is wrong, and does
not change over time. VFSOC however, which uses the voltage fuel gauge
to determine the state of charge, always shows an accurate value.

At least one max170xx driver, found in Asus' Z00D kernel [1], chooses
how to get the capacity based on if current sense is available or not.
Lets change the mainline driver to match the Asus Z00D driver's
behaviour and thereby fix so that correct state of charge values are
obtained on Galaxy S3.

[1] https://github.com/LineageOS/android_kernel_asus_Z00D/blob/c7ab0e3ec5b5/drivers/power/max17042_battery.c#L1103-L1105

Suggested-by: Wolfgang Wiedmeyer <wolfgit@wiedmeyer.de>
Signed-off-by: Henrik Grimler <henrik@grimler.se>
---
drivers/power/supply/max17042_battery.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/power/supply/max17042_battery.c b/drivers/power/supply/max17042_battery.c
index 622bdae6182c..7233670978d0 100644
--- a/drivers/power/supply/max17042_battery.c
+++ b/drivers/power/supply/max17042_battery.c
@@ -317,7 +317,10 @@ static int max17042_get_property(struct power_supply *psy,
val->intval = data * 625 / 8;
break;
case POWER_SUPPLY_PROP_CAPACITY:
- ret = regmap_read(map, MAX17042_RepSOC, &data);
+ if (chip->pdata->enable_current_sense)
+ ret = regmap_read(map, MAX17042_RepSOC, &data);
+ else
+ ret = regmap_read(map, MAX17042_VFSOC, &data);
if (ret < 0)
return ret;

--
2.33.0