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Date:   Tue, 8 Dec 2020 11:10:52 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Michael Klein <michael@...sekall.de>
Cc:     Sebastian Reichel <sre@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/3] power: reset: new driver regulator-poweroff

On Mon, Dec 07, 2020 at 03:27:54PM +0100, Michael Klein wrote:
> This driver registers a pm_power_off function to disable a set of
> regulators defined in the devicetree to turn off the board.
> 
> Signed-off-by: Michael Klein <michael@...sekall.de>
> ---
>  drivers/power/reset/Kconfig              |   7 ++
>  drivers/power/reset/Makefile             |   1 +
>  drivers/power/reset/regulator-poweroff.c | 107 +++++++++++++++++++++++
>  3 files changed, 115 insertions(+)
>  create mode 100644 drivers/power/reset/regulator-poweroff.c
> 
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index d55b3727e00e..ae6cb7b0bd4d 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -177,6 +177,13 @@ config POWER_RESET_QNAP
>  
>  	  Say Y if you have a QNAP NAS.
>  
> +config POWER_RESET_REGULATOR
> +	bool "Regulator subsystem power-off driver"
> +	depends on OF && REGULATOR
> +	help
> +	  This driver supports turning off your board by disabling a set
> +	  of regulators defined in the devicetree.
> +
>  config POWER_RESET_RESTART
>  	bool "Restart power-off driver"
>  	help
> diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
> index c51eceba9ea3..9dc49d3a57ff 100644
> --- a/drivers/power/reset/Makefile
> +++ b/drivers/power/reset/Makefile
> @@ -19,6 +19,7 @@ obj-$(CONFIG_POWER_RESET_OCELOT_RESET) += ocelot-reset.o
>  obj-$(CONFIG_POWER_RESET_PIIX4_POWEROFF) += piix4-poweroff.o
>  obj-$(CONFIG_POWER_RESET_LTC2952) += ltc2952-poweroff.o
>  obj-$(CONFIG_POWER_RESET_QNAP) += qnap-poweroff.o
> +obj-$(CONFIG_POWER_RESET_REGULATOR) += regulator-poweroff.o
>  obj-$(CONFIG_POWER_RESET_RESTART) += restart-poweroff.o
>  obj-$(CONFIG_POWER_RESET_ST) += st-poweroff.o
>  obj-$(CONFIG_POWER_RESET_VERSATILE) += arm-versatile-reboot.o
> diff --git a/drivers/power/reset/regulator-poweroff.c b/drivers/power/reset/regulator-poweroff.c
> new file mode 100644
> index 000000000000..df2ca4fdcc49
> --- /dev/null
> +++ b/drivers/power/reset/regulator-poweroff.c
> @@ -0,0 +1,107 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Force-disables a regulator to power down a device
> + *
> + * Michael Klein <michael@...sekall.de>
> + *
> + * Copyright (C) 2020 Michael Klein
> + *
> + * Based on the gpio-poweroff driver.
> + */
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regulator/consumer.h>
> +
> +#define DEFAULT_TIMEOUT_MS 3000
> +
> +/*
> + * Hold configuration here, cannot be more than one instance of the driver
> + * since pm_power_off itself is global.
> + */
> +static struct regulator **poweroff_regulators;
> +static u32 timeout = DEFAULT_TIMEOUT_MS;
> +
> +static void regulator_poweroff_do_poweroff(void)
> +{
> +	struct regulator **it;
> +
> +	if (poweroff_regulators)
> +		for (it = poweroff_regulators; *it; ++it)
> +			if (regulator_is_enabled(*it))
> +				regulator_force_disable(*it);
> +
> +	/* give it some time */
> +	mdelay(timeout);
> +
> +	WARN_ON(1);
> +}
> +
> +static int regulator_poweroff_probe(struct platform_device *pdev)
> +{
> +	int count;
> +	const char *name;
> +	struct regulator **it;
> +	struct property *prop;
> +	struct device_node *node = pdev->dev.of_node;
> +
> +	/* If a pm_power_off function has already been added, leave it alone */
> +	if (pm_power_off != NULL) {
> +		dev_err(&pdev->dev,
> +			"%s: pm_power_off function already registered\n",
> +		       __func__);
> +		return -EBUSY;
> +	}
> +
> +	count = of_property_count_strings(node, "regulator-names");
> +	if (count <= 0)
> +		return -ENOENT;
> +
> +	poweroff_regulators = devm_kcalloc(&pdev->dev, count + 1,
> +		sizeof(struct regulator *), GFP_KERNEL);
> +
> +	it = poweroff_regulators;
> +	of_property_for_each_string(node, "regulator-names", prop, name) {
> +		*it = devm_regulator_get(&pdev->dev, name);
> +		if (IS_ERR(*it))
> +			return PTR_ERR(*it);
> +		it++;
> +	}
> +
> +	of_property_read_u32(node, "timeout-ms", &timeout);
> +
> +	pm_power_off = &regulator_poweroff_do_poweroff;
> +	return 0;
> +}
> +
> +static int regulator_poweroff_remove(__maybe_unused struct platform_device *pdev)
> +{
> +	if (pm_power_off == &regulator_poweroff_do_poweroff)
> +		pm_power_off = NULL;
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id of_regulator_poweroff_match[] = {
> +	{ .compatible = "regulator-poweroff", },
> +	{},
> +};
> +
> +static struct platform_driver regulator_poweroff_driver = {
> +	.probe = regulator_poweroff_probe,
> +	.remove = regulator_poweroff_remove,
> +	.driver = {
> +		.name = "poweroff-regulator",
> +		.of_match_table = of_regulator_poweroff_match,
> +	},
> +};
> +
> +module_platform_driver(regulator_poweroff_driver);

Since this can't be compiled as a module, you can use
module_platform_driver_probe instead.

Maxime

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