linux-kernel - Re: [PATCH v4 02/10] pinctrl: axp209: add pinctrl features

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Date:   Tue, 5 Dec 2017 09:53:40 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Quentin Schulz <quentin.schulz@...e-electrons.com>
Cc:     linus.walleij@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        wens@...e.org, linux@...linux.org.uk, lee.jones@...aro.org,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        thomas.petazzoni@...e-electrons.com, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v4 02/10] pinctrl: axp209: add pinctrl features

Hi,

On Mon, Dec 04, 2017 at 09:07:52AM +0100, Quentin Schulz wrote:
> >> +static int axp20x_pmx_set_mux(struct pinctrl_dev *pctldev,
> >> +			      unsigned int function, unsigned int group)
> >> +{
> >> +	struct axp20x_gpio *gpio = pinctrl_dev_get_drvdata(pctldev);
> >> +	unsigned int mask;
> >> +
> >> +	/* Every pin supports GPIO_OUT and GPIO_IN functions */
> >> +	if (function <= AXP20X_FUNC_GPIO_IN)
> >> +		return axp20x_pmx_set(pctldev, group,
> >> +				      gpio->funcs[function].muxval);
> >> +
> >> +	if (function == AXP20X_FUNC_LDO)
> >> +		mask = gpio->desc->ldo_mask;
> >> +	else
> >> +		mask = gpio->desc->adc_mask;
> > 
> > What is the point of this test...
> > 
> >> +	if (!(BIT(group) & mask))
> >> +		return -EINVAL;
> >> +
> >> +	/*
> >> +	 * We let the regulator framework handle the LDO muxing as muxing bits
> >> +	 * are basically also regulators on/off bits. It's better not to enforce
> >> +	 * any state of the regulator when selecting LDO mux so that we don't
> >> +	 * interfere with the regulator driver.
> >> +	 */
> >> +	if (function == AXP20X_FUNC_LDO)
> >> +		return 0;
> > 
> > ... if you know that you're not going to do anything with one of the
> > outcomes. It would be better to just move that part above, instead of
> > doing the same test twice.
> > 
> 
> Return value is different. In one case, it is an error to request "ldo"
> for a pin that does not support it. In the other case, the ldo request
> is valid but nothing's done on driver side.
> 
> Both cases are handled differently by the core:
> http://elixir.free-electrons.com/linux/latest/source/drivers/pinctrl/pinmux.c#L439
> 
> I think that's the behavior we're expecting from this driver.

Ah, right.

> Or maybe you're asking to do:
> 
> +	if (function == AXP20X_FUNC_LDO) {
> +		if (!(BIT(group) & gpio->desc->ldo_mask))
> +			return -EINVAL;
> +		return 0;
> +	} else if (!(BIT(group) & gpio->desc->adc_mask)) {
> +		return -EINVAL;
> +	}
> 
> ?

No, it's definitely better the way you did it.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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