linux-kernel - Re: [PATCH 3/3] power: supply: max8997

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Message-ID: <20210201180335.rrsqfvbcmxvx64gf@kozik-lap>
Date:   Mon, 1 Feb 2021 19:03:35 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Timon Baetz <timon.baetz@...tonmail.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 3/3] power: supply: max8997_charger: Switch to new binding

On Mon, Feb 01, 2021 at 09:26:42AM +0000, Timon Baetz wrote:
> 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@...tonmail.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.

Good point.

> 
> > >  	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.

Indeed, thanks for clarification. Looks good:

Reviewed-by: Krzysztof Kozlowski <krzk@...nel.org>

Best regards,
Krzysztof