linux-kernel - Re: [PATCH v2 4/4] power: bq25890_charger.c: Read back the current battery voltage

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Message-ID: <551b84dd28cba9bf7ca7e2f52c9d1901@www.akkea.ca>
Date:   Fri, 27 Jul 2018 09:30:31 -0600
From:   Angus Ainslie <angus@...ea.ca>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     angus.ainslie@...i.sm, Sebastian Reichel <sre@...nel.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] power: bq25890_charger.c: Read back the current  battery voltage

On 2018-07-26 01:03, Krzysztof Kozlowski wrote:
> On 25 July 2018 at 21:46, Angus Ainslie (Purism) <angus@...ea.ca> 
> wrote:
>> The part has the capability of reading the current battery voltage
>> 
>> Signed-off-by: Angus Ainslie (Purism) <angus@...ea.ca>
>> ---
>>  drivers/power/supply/bq25890_charger.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>> 
>> diff --git a/drivers/power/supply/bq25890_charger.c 
>> b/drivers/power/supply/bq25890_charger.c
>> index f4cf2987996b..60ccd6c2b7ad 100644
>> --- a/drivers/power/supply/bq25890_charger.c
>> +++ b/drivers/power/supply/bq25890_charger.c
>> @@ -464,6 +464,20 @@ static int 
>> bq25890_power_supply_get_property(struct power_supply *psy,
>>                 val->intval = bq25890_find_val(bq->init_data.iterm, 
>> TBL_ITERM);
>>                 break;
>> 
>> +       case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>> +               if (!state.online) {
>> +                       val->intval = 0;
>> +                       break;
>> +               }
> 
> You use state from cached value (from last interrupt) but the voltage
> is read directly from registers. The driver follows this convention in
> few other places so maybe it is okay. It depends how accurately the
> interrupts are generated - on every change? IOW, is always guaranteed
> that state will be consistent with values read below?
> 

Well I shouldn't even be checking state here as the VOLTAGE_NOW should 
be valid without it. I'll drop that check.

( Krzysztof sorry for the duplicate email )

> Best regards,
> Krzysztof
> 
>> +
>> +               ret = bq25890_field_read(bq, F_SYSV); /* read measured 
>> value */
>> +               if (ret < 0)
>> +                       return ret;
>> +
>> +               /* converted_val = 2.304V + ADC_val * 20mV (table 
>> 10.3.15) */
>> +               val->intval = 2304000 + ret * 20000;
>> +               break;
>> +
>>         default:
>>                 return -EINVAL;
>>         }
>> @@ -672,6 +686,7 @@ static enum power_supply_property 
>> bq25890_power_supply_props[] = {
>>         POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE,
>>         POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE_MAX,
>>         POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT,
>> +       POWER_SUPPLY_PROP_VOLTAGE_NOW,
>>  };
>> 
>>  static char *bq25890_charger_supplied_to[] = {
>> --
>> 2.17.1
>>