Re: [PATCH resend v2] power: supply: bq27xxx: enable writing capacity values for bq27421

[H. Nikolaus Schaller]

Hi Liam,

> Am 30.08.2017 um 13:24 schrieb Liam Breck <liam@xxxxxxxxxxxxxxxxx>:
> 
> Hi Nikolaus,
> 
> On Wed, Aug 30, 2017 at 2:30 AM, H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> wrote:
>> Hi Liam and Sebastian,
>> 
>>> Am 29.08.2017 um 22:20 schrieb Liam Breck <liam@xxxxxxxxxxxxxxxxx>:
>>> 
>>> Hi Nikolaus, thanks for the patch...
>>> 
>>> On Tue, Aug 29, 2017 at 1:10 PM, H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> wrote:
>>>> Tested on Pyra prototype with bq27421.
>>>> 
>>>> Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
>>>> ---
>>>> drivers/power/supply/bq27xxx_battery.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>> 
>>>> diff --git a/drivers/power/supply/bq27xxx_battery.c b/drivers/power/supply/bq27xxx_battery.c
>>>> index b6c3120ca5ad..e3c878ef7c7e 100644
>>>> --- a/drivers/power/supply/bq27xxx_battery.c
>>>> +++ b/drivers/power/supply/bq27xxx_battery.c
>>>> @@ -688,7 +688,7 @@ static struct bq27xxx_dm_reg bq27545_dm_regs[] = {
>>>> #define bq27545_dm_regs 0
>>>> #endif
>>>> 
>>>> -#if 0 /* not yet tested */
>>>> +#if 1 /* tested on Pyra */
>>>> static struct bq27xxx_dm_reg bq27421_dm_regs[] = {
>>> 
>>> I think we can drop the #if and #else...#endif so it's just the
>>> dm_regs table, as with bq27425.
>> 
>> I have fixed that and did take the chance to update my OpenPandora
>> kernel so that I also could test and make the bq27500 working.
> 
> Is this gauge on the board or in the battery?

It is on the board.

> If in the battery,
> monitored-battery should not be used.
> 
> For a gauge on the board, if a user changes the battery to a different
> type, they need to update the dtb.

Well, that is a little difficult to control, but here we have only
one standard Pandora cell. There may exist replacements with different
capacity, but that should not be our problem...

> 
> I assume you built with config_battery_bq27xxx_dt_updates_nvm?

Yes.

> 
>> The biggest hurdle was to find out that I have to change the
>> compatible string to "ti,bq27500-1" to get non-NULL dm_regs...
>> 
>> [   12.765930] bq27xxx_battery_i2c_probe name=bq27500-1-0
>> [   12.771392] bq27xxx_battery_i2c_probe call setup
>> [   12.874816] bq27xxx_battery_setup
>> [   12.904266] bq27xxx_battery_setup: dm_regs=bf0520e0
>> [   12.933380] (NULL device *): hwmon: 'bq27500-1-0' is not a valid name attribute, please fix
>> [   13.234893] bq27xxx_battery_settings
>> [   13.238891] bq27xxx-battery 2-0055: invalid battery:energy-full-design-microwatt-hours 14800000
> 
> The chip does not support this param, so it should be zero, as it has
> to be set if charge-full-design-* is set. Can you try that?

Hm. IMHO the DT should describe what the battery has and the driver should simply ignore
values it can't handle or reject them but do the best out of it. Telling the driver to ignore
a value by setting to 0 would IMHO be the wrong approach.

We are also working on the generic-adc-battery driver that makes use of the same battery DT
node so that people can choose if they want to configure a kernel for fuel gauge or
g-a-b or even both.

> 
>> [   13.312469] bq27xxx_battery_set_config
>> [   13.407745] bq27xxx_battery_unseal
>> [   13.455993] bq27xxx_battery_update_dm_block
>> [   13.460418] bq27xxx-battery 2-0055: update terminate-voltage to 3200
>> [   13.694885] bq27xxx_battery_seal
> 
> We need to see output after a reboot.

This was the value after first boot with the new driver enabled.

A second boot after removing and reinserting battery shows:

[   11.256713] bq27xxx_battery_setup
[   11.256744] bq27xxx_battery_setup: dm_regs=bf05b0e0
[   11.257690] (NULL device *): hwmon: 'bq27500-1-0' is not a valid name attribute, please fix
[   11.258056] bq27xxx_battery_settings
[   11.258300] bq27xxx-battery 2-0055: invalid battery:energy-full-design-microwatt-hours 14800000
[   11.258300] bq27xxx_battery_set_config
[   11.258331] bq27xxx_battery_unseal

> Note that this chip has NVM so
> these settings persist without power.

Yes I know. Up to now the bq27500 has been programmed during production test
by some special flashing tool. Now as the kernel driver has this capability,
we should make (optionally) use of it.

> 
>> Does this look ok for
>> 
>>        bat: battery {
>>                compatible = "simple-battery", "openpandora-battery";
>>                voltage-min-design-microvolt = <3200000>;
>>                energy-full-design-microwatt-hours = <14800000>;
>>                charge-full-design-microamp-hours = <4000000>;
>>        };
>> 
>> ?

I mainly had some initial doubts that it did not tell something like
"update design-capacity" to 4000 or "design-capacity has 4000"

Ah, I see:

		/* assume design energy & capacity are in same block */

This means the bq27500 never programs capacity because we can't specify energy.
So I't suggest to revise this rule and coupling of energy and capacity setting.

>> 
>> I will send a patch for enabling both fuel gauges and the omap3-pandora-common.dtsi asap.
> 
> You probably don't want this in upstream dts, as it only programs the
> gauge if the kernel has the above config option. If the box runs a
> stock distro, it won't work. A custom-built kernel with the above dts
> programs the gauge unless the user sets the module param
> dt_monitored_battery_updates_nvm=0. The requisite dtb should be
> packaged with the custom-built kernel, and deployed with awareness of
> the actual battery present.

Imho, DT can and should describe all properties of the standard OpenPandora
battery (and not missing registers of the bq27500).

Using this information or not should be defined by different defconfigs.

Anyways I have now collected my patches into a patch set for further
review and cherry-picking.

BR,
Nikolaus