linux-kernel - Re: [PATCH v2 1/2] usb: ehci-exynos: Make provision for vdd regulators

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Date:	Thu, 12 Jun 2014 13:21:09 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Alan Stern' <stern@...land.harvard.edu>,
	'Vivek Gautam' <gautam.vivek@...sung.com>
Cc:	linux-usb@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, kgene.kim@...sung.com,
	'Jingoo Han' <jg1.han@...sung.com>
Subject: Re: [PATCH v2 1/2] usb: ehci-exynos: Make provision for vdd regulators

On Thursday, June 12, 2014 12:39 AM, Alan Stern wrote:
> On Fri, 6 Jun 2014, Vivek Gautam wrote:
> 
> > Facilitate getting required 3.3V and 1.0V VDD supply for
> > EHCI controller on Exynos.
> >
> > With patches for regulators' nodes merged in 3.15:
> > c8c253f ARM: dts: Add regulator entries to smdk5420
> > 275dcd2 ARM: dts: add max77686 pmic node for smdk5250,
> >
> > certain perripherals will now need to ensure that,
> > they request VDD regulators in their drivers, and enable
> > them so as to make them working.
> 
> "Certain peripherals"?  Don't you mean "certain controllers"?
> 
> Does this mean some controllers don't need to use the VDD regulators?
> 
> > @@ -193,7 +196,31 @@ static int exynos_ehci_probe(struct platform_device *pdev)
> >
> >  	err = exynos_ehci_get_phy(&pdev->dev, exynos_ehci);
> >  	if (err)
> > -		goto fail_clk;
> > +		goto fail_regulator1;
> > +
> > +	exynos_ehci->vdd33 = devm_regulator_get(&pdev->dev, "vdd33");
> > +	if (!IS_ERR(exynos_ehci->vdd33)) {
> > +		err = regulator_enable(exynos_ehci->vdd33);
> > +		if (err) {
> > +			dev_err(&pdev->dev,
> > +				"Failed to enable 3.3V Vdd supply\n");
> > +			goto fail_regulator1;
> > +		}
> > +	} else {
> > +		dev_warn(&pdev->dev, "Regulator 3.3V Vdd supply not found\n");
> > +	}
> 
> What if this is one of the controllers that don't need to use a VDD
> regulator?  Do you really want to print out a warning in that case?
> Should you call devm_regulator_get_optional() instead?

I agree with Alan's suggestion. This warning message is not
proper, when USB controllers that don't need a VDD regulator
are used. The devm_regulator_get_optional() looks better.

Best regards,
Jingoo Han


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