Re: [PATCH 3/3] power: supply: max8997_charger: Switch to new binding

From: Timon Baetz <timon.baetz@protonmail.com>
To: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Sebastian Reichel <sre@kernel.org>,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 3/3] power: supply: max8997_charger: Switch to new binding
Date: Mon, 01 Feb 2021 09:26:42 +0000	[thread overview]
Message-ID: <20210201083128.18499ffd.timon.baetz@protonmail.com> (raw)
In-Reply-To: <20210131172840.fxaadhhsafa4aeex@kozik-lap>

On Sun, 31 Jan 2021 18:28:40 +0100, Krzysztof Kozlowski wrote:
> On Sat, Jan 30, 2021 at 05:30:14PM +0000, Timon Baetz wrote:
> > Get regulator from parent device's node and extcon by name.
> >
> > Signed-off-by: Timon Baetz <timon.baetz@protonmail.com>
> > ---
> >  drivers/power/supply/max8997_charger.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/power/supply/max8997_charger.c b/drivers/power/supply/max8997_charger.c
> > index 321bd6b8ee41..625d8cc4312a 100644
> > --- a/drivers/power/supply/max8997_charger.c
> > +++ b/drivers/power/supply/max8997_charger.c
> > @@ -168,6 +168,7 @@ static int max8997_battery_probe(struct platform_device *pdev)
> >  	int ret = 0;
> >  	struct charger_data *charger;
> >  	struct max8997_dev *iodev = dev_get_drvdata(pdev->dev.parent);
> > +	struct device_node *np = pdev->dev.of_node;
> >  	struct i2c_client *i2c = iodev->i2c;
> >  	struct max8997_platform_data *pdata = iodev->pdata;
> >  	struct power_supply_config psy_cfg = {};
> > @@ -237,20 +238,23 @@ static int max8997_battery_probe(struct platform_device *pdev)
> >  		return PTR_ERR(charger->battery);
> >  	}
> >
> > +	// grab regulator from parent device's node
> > +	pdev->dev.of_node = iodev->dev->of_node;
> >  	charger->reg = devm_regulator_get_optional(&pdev->dev, "charger");
> > +	pdev->dev.of_node = np;  
> 
> I think the device does not have its own node anymore. Or did I miss
> something?

The idea is to reset of_node to whatever it was before (NULL) and basically 
leave the device unchanged. Probe might run again because of deferral.

> >  	if (IS_ERR(charger->reg)) {
> >  		if (PTR_ERR(charger->reg) == -EPROBE_DEFER)
> >  			return -EPROBE_DEFER;
> >  		dev_info(&pdev->dev, "couldn't get charger regulator\n");
> >  	}
> > -	charger->edev = extcon_get_edev_by_phandle(&pdev->dev, 0);
> > -	if (IS_ERR(charger->edev)) {
> > -		if (PTR_ERR(charger->edev) == -EPROBE_DEFER)
> > +	charger->edev = extcon_get_extcon_dev("max8997-muic");
> > +	if (IS_ERR_OR_NULL(charger->edev)) {
> > +		if (!charger->edev)  
> 
> Isn't NULL returned when there is simply no extcon? It's different than
> deferred probe. Returning here EPROBE_DEFER might lead to infinite probe
> tries (on every new device probe) instead of just failing it.

extcon_get_extcon_dev() just loops through all registered extcon devices
and compared names. It will return NULL when "max8997-muic" isn't
registered yet. extcon_get_extcon_dev() never returns EPROBE_DEFER so
checking for NULL seems to be the only way. Other drivers using that
function also do NULL check and return EPROBE_DEFER.

Thanks for reviewing,
Timon