Re: [PATCH 1/2] power: supply: Use the scope of power supplies to tell if power is system supplied

[Limonciello, Mario]

On 5/16/2023 3:41 PM, Sebastian Reichel wrote:
> Hi,
>
> On Tue, May 16, 2023 at 01:25:40PM -0500, Mario Limonciello wrote:
> > The logic used for power_supply_is_system_supplied() counts all power
> > supplies and:
> > * If no power supplies found assumes AC
> > * If non-battery power supplies found uses online to determine AC/DC.
> >    - If any are onlined, assumes AC
> >    - Othewise DC.
> >
> > This logic makes sense for desktop systems that don't export an ACPI
> > battery, but it fails once you include a dGPU that provides a UCSI
> > power supply on a desktop system without any other power supplies.
> >
> > The dGPU by default doesn't have anything plugged in so it's 'offline'.
> > This makes power_supply_is_system_supplied() return 0 with a count of
> > 1 meaning all drivers that use this get a wrong judgement.
> >
> > To fix this case adjust the logic to also examine the scope of the
> > power supply. If the power supply is deemed a device power supply,
> > then don't count it.
> >
> > Cc: Evan Quan <Evan.Quan@xxxxxxx>
> > Suggested-by: Lijo Lazar <Lijo.Lazar@xxxxxxx>
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> Good find; the current logic should also break with a desktop PC
> once a POWER_SUPPLY_SCOPE_DEVICE battery device is attached (e.g.
> a HID device), because it increases the counter.

Yup!

> I suppose I can just apply this to my fixes branch since there is
> no compile time dependency to the second patch?

Yes, that's correct.  I don't see a problem with the other patch going 
through
another tree.

> -- Sebastian
>
> >   drivers/power/supply/power_supply_core.c | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> > index ab986dbace16..d57f420ba8c3 100644
> > --- a/drivers/power/supply/power_supply_core.c
> > +++ b/drivers/power/supply/power_supply_core.c
> > @@ -348,6 +348,10 @@ static int __power_supply_is_system_supplied(struct device *dev, void *data)
> >   	struct power_supply *psy = dev_get_drvdata(dev);
> >   	unsigned int *count = data;
> >   
> > +	if (!psy->desc->get_property(psy, POWER_SUPPLY_PROP_SCOPE, &ret))
> > +		if (ret.intval == POWER_SUPPLY_SCOPE_DEVICE)
> > +			return 0;
> > +
> >   	(*count)++;
> >   	if (psy->desc->type != POWER_SUPPLY_TYPE_BATTERY)
> >   		if (!psy->desc->get_property(psy, POWER_SUPPLY_PROP_ONLINE,
> > @@ -366,8 +370,8 @@ int power_supply_is_system_supplied(void)
> >   				      __power_supply_is_system_supplied);
> >   
> >   	/*
> > -	 * If no power class device was found at all, most probably we are
> > -	 * running on a desktop system, so assume we are on mains power.
> > +	 * If no system scope power class device was found at all, most probably we
> > +	 * are running on a desktop system, so assume we are on mains power.
> >   	 */
> >   	if (count == 0)
> >   		return 1;
> > --
> > 2.34.1