Re: [PATCH 1/2] power:bq27xxx: fix reading for bq27000 and bq27010

From: Andrew F. Davis
Date: Wed Dec 23 2015 - 21:48:32 EST


On 12/17/2015 04:12 AM, H. Nikolaus Schaller wrote:
bug: the driver reports funny capacity values:

root@letux:/sys/class/power_supply/bq27000-battery# cat uevent
POWER_SUPPLY_NAME=bq27000-battery
POWER_SUPPLY_STATUS=Charging
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_VOLTAGE_NOW=3702000
POWER_SUPPLY_CURRENT_NOW=-464635
POWER_SUPPLY_CAPACITY=1536 <- over 100% is magic
POWER_SUPPLY_CAPACITY_LEVEL=Normal
POWER_SUPPLY_TEMP=311
POWER_SUPPLY_TIME_TO_FULL_NOW=10440
POWER_SUPPLY_TECHNOLOGY=Li-ion
POWER_SUPPLY_CHARGE_FULL=805450
POWER_SUPPLY_CHARGE_NOW=1068
POWER_SUPPLY_CHARGE_FULL_DESIGN=8844998 <- battery has just 1200 mAh
POWER_SUPPLY_CYCLE_COUNT=21
POWER_SUPPLY_ENERGY_NOW=0
POWER_SUPPLY_POWER_AVG=0
POWER_SUPPLY_HEALTH=Good
POWER_SUPPLY_MANUFACTURER=Texas Instruments

reason: the state of charge and the design capacity register are single
byte only. The design capacity returns the higer order byte.

tested: GTA04 with Openmoko/FIC HF08x battery (using hdq)

Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
---
drivers/power/bq27xxx_battery.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/power/bq27xxx_battery.c b/drivers/power/bq27xxx_battery.c
index 880233c..e54a125 100644
--- a/drivers/power/bq27xxx_battery.c
+++ b/drivers/power/bq27xxx_battery.c
@@ -471,7 +471,10 @@ static int bq27xxx_battery_read_soc(struct bq27xxx_device_info *di)
{
int soc;

- soc = bq27xxx_read(di, BQ27XXX_REG_SOC, false);
+ if (di->chip == BQ27000 || di->chip == BQ27010)
+ soc = bq27xxx_read(di, BQ27XXX_REG_SOC, true);
+ else
+ soc = bq27xxx_read(di, BQ27XXX_REG_SOC, false);

if (soc < 0)
dev_dbg(di->dev, "error reading State-of-Charge\n");
@@ -536,7 +539,10 @@ static int bq27xxx_battery_read_dcap(struct bq27xxx_device_info *di)
{
int dcap;

- dcap = bq27xxx_read(di, BQ27XXX_REG_DCAP, false);
+ if (di->chip == BQ27000 || di->chip == BQ27010)
+ dcap = bq27xxx_read(di, BQ27XXX_REG_DCAP, true);
+ else
+ dcap = bq27xxx_read(di, BQ27XXX_REG_DCAP, false);


I'm wondering how the I2C versions will be effected by this change, will
we get the right byte when we only read one? Maybe the fix should be
to still read 2-bytes but mask out the right bits from the result? The
data-sheet doesn't seem clear on this.

Well, it is more right than it was before, I'll look for a bq27200 to
test and make changes if needed some other time, but for now:

Acked-by: Andrew F. Davis <afd@xxxxxx>

if (dcap < 0) {
dev_dbg(di->dev, "error reading initial last measured discharge\n");
@@ -544,7 +550,7 @@ static int bq27xxx_battery_read_dcap(struct bq27xxx_device_info *di)
}

if (di->chip == BQ27000 || di->chip == BQ27010)
- dcap *= BQ27XXX_CURRENT_CONSTANT / BQ27XXX_RS;
+ dcap = (dcap << 8) * BQ27XXX_CURRENT_CONSTANT / BQ27XXX_RS;
else
dcap *= 1000;



--
Andrew F. Davis
--
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