Re: [PATCH v3 1/3] power: reset: new driver regulator-poweroff

[Michael Klein]

On Tue, Dec 08, 2020 at 11:10:52AM +0100, Maxime Ripard wrote:
> 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@xxxxxxxxxxxx>
> > ---
> >  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@xxxxxxxxxxxx>
> > + *
> > + * 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.

actually no, as platform_driver_probe() does not support deferred 
probing and the regulator might not be available during 
regulator_poweroff_probe() yet:

# dmesg | grep poweroff
[    0.788135] poweroff-regulator poweroff: probe deferral not supported

--
Michael