linux-kernel - Re: [PATCH v7 08/24] mfd: max77686: Add Dynamic Voltage Scaling (DVS) support

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Date:	Thu, 10 Jul 2014 11:46:20 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Lee Jones <lee.jones@...aro.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Mike Turquette <mturquette@...aro.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Yadwinder Singh Brar <yadi.brar01@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Doug Anderson <dianders@...omium.org>,
	Tushar Behera <trblinux@...il.com>,
	Mark Brown <broonie@...nel.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Olof Johansson <olof@...om.net>,
	Andreas Farber <afaerber@...e.de>,
	Alexandre Courbot <gnurou@...il.com>,
	Rob Jones <rob.jones@...ethink.co.uk>
Subject: Re: [PATCH v7 08/24] mfd: max77686: Add Dynamic Voltage Scaling (DVS) support

On Fri, Jul 4, 2014 at 10:24 PM, Javier Martinez Canillas
<javier.martinez@...labora.co.uk> wrote:

> Some regulators on the MAX77686 PMIC have Dynamic Voltage Scaling
> (DVS) support that allows output voltage to change dynamically.
>
> For MAX77686, these regulators are Buck regulators 2, 3 and 4.
>
> Each Buck output voltage is selected using a set of external
> inputs: DVS1-3 and SELB2-4.
>
> DVS registers can be used to configure the output voltages for each
> Buck regulator and which one is active is controled by DVSx lines.
>
> SELBx lines are used to control if individual Buck lines are ON or OFF.
>
> This patch adds support to configure the DVSx and SELBx lines
> from DT and to setup and read the GPIO lines connected to them.
>
> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

(...)
> +#include <linux/gpio/consumer.h>

THANKS for using modern interfaces!

> +static void max77686_dt_parse_dvs_gpio(struct device *dev)
> +{
> +       struct max77686_platform_data *pd = dev_get_platdata(dev);
> +       int i;
> +
> +       /*
> +        * NOTE: we don't consider GPIO errors fatal; board may have some lines
> +        * directly pulled high or low and thus doesn't specify them.
> +        */
> +       for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_dvs); i++)
> +               pd->buck_gpio_dvs[i] =
> +                       devm_gpiod_get_index(dev, "max77686,pmic-buck-dvs", i);
> +
> +       for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++)
> +               pd->buck_gpio_selb[i] =
> +                       devm_gpiod_get_index(dev, "max77686,pmic-buck-selb", i);
> +}

Rob Jones has a patch cooking that adds gpio_get_array() so this thing
merits also adding devm_gpiod_get_array() I think?

> +/**
> + * max77686_setup_gpios() - init DVS-related GPIOs
> + * @dev: device whose platform data contains the dvs GPIOs information
> + *
> + * This function claims / initalizations GPIOs related to DVS if they are
> + * defined. This may have the effect of switching voltages if the
> + * pdata->buck_default_idx does not match the boot time state of pins.
> + */
> +int max77686_setup_gpios(struct device *dev)
> +{
> +       struct max77686_platform_data *pd = dev_get_platdata(dev);
> +       int buck_default_idx = pd->buck_default_idx;
> +       int ret;
> +       int i;
> +
> +       /* Set all SELB high to avoid glitching while DVS is changing */
> +       for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++) {
> +               struct gpio_desc *gpio = pd->buck_gpio_selb[i];
> +
> +               /* OK if some GPIOs aren't defined */
> +               if (IS_ERR(gpio))
> +                       continue;
> +
> +               ret = gpiod_direction_output_raw(gpio, 1);

Why does this have to be raw? Usually that is not to be used.

Apart from this it looks OK.

Yours,
Linus Walleij
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