linux-kernel - Re: [PATCH v2] power/supply: ingenic-battery: Don't change scale if there's only one

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Date:   Sat, 16 Nov 2019 14:54:18 +0100
From:   Paul Cercueil <paul@...pouillou.net>
To:     Artur Rojek <contact@...ur-rojek.eu>
Cc:     Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] power/supply: ingenic-battery: Don't change scale if
 there's only one

Hi Artur,


Le ven., nov. 15, 2019 at 18:39, Artur Rojek <contact@...ur-rojek.eu> a 
écrit :
> Hi Paul.
> Comments inline.
> 
> On 2019-11-14 17:35, Paul Cercueil wrote:
>> The ADC in the JZ4740 can work either in high-precision mode with a 
>> 2.5V
>> range, or in low-precision mode with a 7.5V range. The code in place 
>> in
>> this driver will select the proper scale according to the maximum
>> voltage of the battery.
>> 
>> The JZ4770 however only has one mode, with a 6.6V range. If only one
>> scale is available, there's no need to change it (and nothing to 
>> change
>> it to), and trying to do so will fail with -EINVAL.
>> 
>> Fixes: fb24ccfbe1e0 ("power: supply: add Ingenic JZ47xx battery 
>> driver.")
>> 
>> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>> Cc: stable@...r.kernel.org
>> ---
>> 
>> Notes:
>>     v2: Rebased on v5.4-rc7
>> 
>>  drivers/power/supply/ingenic-battery.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/drivers/power/supply/ingenic-battery.c
>> b/drivers/power/supply/ingenic-battery.c
>> index 35816d4b3012..5a53057b4f64 100644
>> --- a/drivers/power/supply/ingenic-battery.c
>> +++ b/drivers/power/supply/ingenic-battery.c
>> @@ -80,6 +80,10 @@ static int ingenic_battery_set_scale(struct
>> ingenic_battery *bat)
>>  	if (ret != IIO_AVAIL_LIST || scale_type != IIO_VAL_FRACTIONAL_LOG2)
>>  		return -EINVAL;
>> 
>> +	/* Only one (fractional) entry - nothing to change */
>> +	if (scale_len == 2)
>> +		return 0;
>> +
> 
> This function also serves to validate that the maximum voltage is in 
> range of available scales.
> Please move your code down a bit so that the check for max_mV is 
> still being done.

Good point - I'll send a V3.

-Paul

> 
> Thanks,
> Artur
> 
>>  	max_mV = bat->info.voltage_max_design_uv / 1000;
>> 
>>  	for (i = 0; i < scale_len; i += 2) {