Re: [PATCH v2 4/4] power: supply: Add Spreadtrum SC27XX fuel gauge unit driver

[Baolin Wang]

Hi Linus,

On 26 September 2018 at 16:09, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Wed, Sep 26, 2018 at 5:00 AM Baolin Wang <baolin.wang@xxxxxxxxxx> wrote:
>
>> This patch adds the Spreadtrum SC27XX serial PMICs fuel gauge support,
>> which is used to calculate the battery capacity.
>>
>> Original-by: Yuanjiang Yu <yuanjiang.yu@xxxxxxxxxx>
>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
>> ---
>> Changes from v1:
>>  - Use battery standard properties to get internal resistance and ocv table.
>>  - Change devm_gpiod_get_optional() to devm_gpiod_get().
>>  - Add power_supply_changed() when detecting battery present change.
>>  - Return micro volts for sc27xx_fgu_get_vbat_ocv().
>
> Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
>
> I see that you need to have the internal resistance as parameter to
> this equation so it needs to come in. (I guess as factor/typical
> internal resistance as suggested.)
>
> IIUC this reliance on an uncertain internal resistance is the reason
> why fuel gauges / coloumb counters are seen as crude ways to
> estimate battery capacity, and their accuracy and reliability worsen
> over the lifetime of the battery, and this is why safety-critical devices
> include ways to measure the internal resistance as well.

Yes. Thanks for your reviewing.

>
> But the hardware is as it is, and probably for some good reasons,
> like cost.
>
> Yours,
> Linus Walleij



-- 
Baolin Wang
Best Regards