linux-kernel - Re: [PATCH] power: supply: bq256xx: Remove init ichg/vbat with max value

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Date:   Wed, 30 Nov 2022 09:27:42 +0000
From:   Hermes Zhang <Hermes.Zhang@...s.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
CC:     kernel <kernel@...s.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Hermes Zhang <Hermes.Zhang@...s.com>
Subject: Re: [PATCH] power: supply: bq256xx: Remove init ichg/vbat with max
 value

Hi,

在 2022/11/29 23:27, Sebastian Reichel 写道:
> Hi,
>
> On Tue, Nov 29, 2022 at 05:01:12PM +0800, Hermes Zhang wrote:
>> Init the ichg and vbat reg with max value is not good. First the chip
>> already has a default value for ichg and vbat (small value). Init these
>> two reg with max value will result an unsafe case (e.g. battery is over
>> charging in a hot environment) if no user space change them later.
>>
>> Signed-off-by: Hermes Zhang <chenhuiz@...s.com>
>> ---
> It's the driver's task to setup safe initial maximum values.
> Pre-kernel values may or may not be safe if you consider things
> like kexec. If you get unsafe values programmed, then fix the
> values instead.
>
> -- Sebastian

The constant_charge_current_max_ua is either from dts or default value 
for each chip in the code, but I guess I could ot change them because it 
has their own meaning (it will be used to check if the setting is valid 
or not). Do you mean I can set some other value here instead of 
constant_xxx_max?

Best Regards,
Hermes


>>   drivers/power/supply/bq256xx_charger.c | 10 ----------
>>   1 file changed, 10 deletions(-)
>>
>> diff --git a/drivers/power/supply/bq256xx_charger.c b/drivers/power/supply/bq256xx_charger.c
>> index 01ad84fd147c..d1aa92c10c22 100644
>> --- a/drivers/power/supply/bq256xx_charger.c
>> +++ b/drivers/power/supply/bq256xx_charger.c
>> @@ -1562,21 +1562,11 @@ static int bq256xx_hw_init(struct bq256xx_device *bq)
>>   	if (ret)
>>   		return ret;
>>   
>> -	ret = bq->chip_info->bq256xx_set_ichg(bq,
>> -				bat_info->constant_charge_current_max_ua);
>> -	if (ret)
>> -		return ret;
>> -
>>   	ret = bq->chip_info->bq256xx_set_iprechg(bq,
>>   				bat_info->precharge_current_ua);
>>   	if (ret)
>>   		return ret;
>>   
>> -	ret = bq->chip_info->bq256xx_set_vbatreg(bq,
>> -				bat_info->constant_charge_voltage_max_uv);
>> -	if (ret)
>> -		return ret;
>> -
>>   	ret = bq->chip_info->bq256xx_set_iterm(bq,
>>   				bat_info->charge_term_current_ua);
>>   	if (ret)
>> -- 
>> 2.30.2
>>