Re: [PATCH 10/10] power: supply: bq25890: Add new linux,iinlim-percentage property

[Hans de Goede <hdegoede@redhat.com>]

Hi Marek,

On 11/27/22 22:34, Marek Vasut wrote:
> On 11/27/22 19:02, Hans de Goede wrote:
>> Some devices, such as the Lenovo Yoga Tab 3 Pro (YT3-X90F) have
>> multiple batteries with a separate bq25890 charger for each battery.
>>
>> This requires the maximum current the external power-supply can deliver
>> to be divided over the chargers. The Android vendor kernel shipped
>> on the YT3-X90F divides this current with a 40/60 percent split so that
>> batteries are done charging at approx. the same time if both were fully
>> empty at the start.
>>
>> Add support for a new "linux,iinlim-percentage" percentage property which
>> can be set to indicate that a bq25890 charger should only use that
>> percentage of the external power-supply's maximum current.
>>
>> So far this new property is only used on x86/ACPI (non devicetree) devs,
>> IOW it is not used in actual devicetree files. The devicetree-bindings
>> maintainers have requested properties like these to not be added to the
>> devicetree-bindings, so the new property is deliberately not added
>> to the existing devicetree-bindings.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   drivers/power/supply/bq25890_charger.c | 24 +++++++++++++++++++++---
>>   1 file changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/power/supply/bq25890_charger.c b/drivers/power/supply/bq25890_charger.c
>> index b0d07ff24ace..2bd7721b969f 100644
>> --- a/drivers/power/supply/bq25890_charger.c
>> +++ b/drivers/power/supply/bq25890_charger.c
>> @@ -126,6 +126,7 @@ struct bq25890_device {
>>       bool read_back_init_data;
>>       bool force_hiz;
>>       u32 pump_express_vbus_max;
>> +    u32 iinlim_percentage;
> 
> If this is percentage, u8 should be enough, right ?

It is not a charger-chip register value and it is used in
calculations so it is best if this is native integer size.

And I was passing its address directly to device_property_read_u32(),
but that has changed in v2.

>>       enum bq25890_chip_version chip_version;
>>       struct bq25890_init_data init_data;
>>       struct bq25890_state state;
>> @@ -727,6 +728,18 @@ static int bq25890_power_supply_property_is_writeable(struct power_supply *psy,
>>       }
>>   }
>>   +/*
>> + * If there are multiple chargers the maximum current the external power-supply
>> + * can deliver needs to be divided over the chargers. This is done according
>> + * to the bq->iinlim_percentage setting.
>> + */
>> +static int bq25890_charger_get_scaled_iinlim_regval(struct bq25890_device *bq,
>> +                            int iinlim_ua)
>> +{
>> +    iinlim_ua = iinlim_ua * bq->iinlim_percentage / 100;
> 
> Can this ever add up to value above 100 ?
> Should this use some clamp() ?

bq->iinlim_percentage should never be more then 100. I have added a check
for this when reading the property for version 2 of the series.

Thank you for all the reviews. I've also addressed all your other small
remarks and I will send out a v2 series with these fixed.

Regards,

Hans



> 
>> +    return bq25890_find_idx(iinlim_ua, TBL_IINLIM);
>> +}
>> +
>>   /* On the BQ25892 try to get charger-type info from our supplier */
>>   static void bq25890_charger_external_power_changed(struct power_supply *psy)
>>   {
> 
> [...]
>