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Date: Sat, 11 Jan 2020 10:50:55 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Andreas Klinger <ak@...klinger.de>
Cc: robh+dt@...nel.org, mark.rutland@....com, knaack.h@....de,
lars@...afoo.de, pmeerw@...erw.net, rpi-receiver@...-steyr.ac.at,
linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: srf04: add power management feature
On Thu, 9 Jan 2020 09:39:28 +0100
Andreas Klinger <ak@...klinger.de> wrote:
> Add suspend and resume operations for being used by optional power
> management.
>
> The suspend function is switching off an GPIO which can be used by the
> hardware to switch power off. The resume function is switching the GPIO
> on and sleeps an adjustable time to give the device a chance to be up
> and running.
>
> If activated the driver gets into autosuspend after some time of
> inactivity.
>
Generally we try to avoid introducing ifdef CONFIG_PM where
possible, because it tends to be error prone. Mostly
marking functions __maybe_unused is sufficient.
Otherwise looks good to me.
Jonathan
> Suggested-by: Franz Parzer <rpi-receiver@...-steyr.ac.at>
> Signed-off-by: Andreas Klinger <ak@...klinger.de>
> ---
> drivers/iio/proximity/srf04.c | 104 +++++++++++++++++++++++++++++++++-
> 1 file changed, 103 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/proximity/srf04.c b/drivers/iio/proximity/srf04.c
> index 01eb8cc63076..b19d910298d6 100644
> --- a/drivers/iio/proximity/srf04.c
> +++ b/drivers/iio/proximity/srf04.c
> @@ -45,6 +45,7 @@
> #include <linux/sched.h>
> #include <linux/interrupt.h>
> #include <linux/delay.h>
> +#include <linux/pm_runtime.h>
> #include <linux/iio/iio.h>
> #include <linux/iio/sysfs.h>
>
> @@ -56,6 +57,7 @@ struct srf04_data {
> struct device *dev;
> struct gpio_desc *gpiod_trig;
> struct gpio_desc *gpiod_echo;
> + struct gpio_desc *gpiod_power;
> struct mutex lock;
> int irqnr;
> ktime_t ts_rising;
> @@ -63,6 +65,7 @@ struct srf04_data {
> struct completion rising;
> struct completion falling;
> const struct srf04_cfg *cfg;
> + int startup_time_ms;
> };
>
> static const struct srf04_cfg srf04_cfg = {
> @@ -97,6 +100,9 @@ static int srf04_read(struct srf04_data *data)
> u64 dt_ns;
> u32 time_ns, distance_mm;
>
> + if (data->gpiod_power)
> + pm_runtime_get_sync(data->dev);
> +
> /*
> * just one read-echo-cycle can take place at a time
> * ==> lock against concurrent reading calls
> @@ -110,6 +116,11 @@ static int srf04_read(struct srf04_data *data)
> udelay(data->cfg->trigger_pulse_us);
> gpiod_set_value(data->gpiod_trig, 0);
>
> + if (data->gpiod_power) {
> + pm_runtime_mark_last_busy(data->dev);
> + pm_runtime_put_autosuspend(data->dev);
> + }
> +
> /* it should not take more than 20 ms until echo is rising */
> ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
> if (ret < 0) {
> @@ -268,6 +279,26 @@ static int srf04_probe(struct platform_device *pdev)
> return PTR_ERR(data->gpiod_echo);
> }
>
> +#ifdef CONFIG_PM
> + data->gpiod_power = devm_gpiod_get_optional(dev, "power",
> + GPIOD_OUT_LOW);
As the gpio is optional anyway and the various runtime pm calls will be stubbed
out if CONFIG_PM is not enabled, it seems to me that we can just always leave
this code in place. So drop the CONFIG_PM protection.
> + if (IS_ERR(data->gpiod_power)) {
> + dev_err(dev, "failed to get power-gpios: err=%ld\n",
> + PTR_ERR(data->gpiod_power));
> + return PTR_ERR(data->gpiod_power);
> + }
> + if (data->gpiod_power) {
> +
> + if (of_property_read_u32(dev->of_node, "startup-time-ms",
> + &data->startup_time_ms))
> + data->startup_time_ms = 100;
> + dev_dbg(dev, "using power gpio: startup-time-ms=%d\n",
> + data->startup_time_ms);
> + }
> +#else
> + data->gpiod_power = NULL;
> +#endif
> +
> if (gpiod_cansleep(data->gpiod_echo)) {
> dev_err(data->dev, "cansleep-GPIOs not supported\n");
> return -ENODEV;
> @@ -296,14 +327,85 @@ static int srf04_probe(struct platform_device *pdev)
> indio_dev->channels = srf04_chan_spec;
> indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
>
> - return devm_iio_device_register(dev, indio_dev);
> + ret = iio_device_register(indio_dev);
> + if (ret < 0) {
> + dev_err(data->dev, "iio_device_register: %d\n", ret);
> + return ret;
> + }
> +
> + if (data->gpiod_power) {
> + pm_runtime_set_autosuspend_delay(data->dev, 1000);
> + pm_runtime_use_autosuspend(data->dev);
> +
> + ret = pm_runtime_set_active(data->dev);
> + if (ret) {
> + dev_err(data->dev, "pm_runtime_set_active: %d\n", ret);
> + iio_device_unregister(indio_dev);
> + }
> +
> + pm_runtime_enable(data->dev);
> + pm_runtime_idle(data->dev);
> + }
> +
> + return ret;
> }
>
> +static int srf04_remove(struct platform_device *pdev)
> +{
> + struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> + struct srf04_data *data = iio_priv(indio_dev);
> +
> + iio_device_unregister(indio_dev);
> +
> + if (data->gpiod_power) {
> + pm_runtime_disable(data->dev);
> + pm_runtime_set_suspended(data->dev);
> + }
> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_PM
If we drop CONFIG_PM these will need to be marked __maybe_unused.
> +static int srf04_pm_runtime_suspend(struct device *dev)
> +{
> + struct platform_device *pdev = container_of(dev,
> + struct platform_device, dev);
> + struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> + struct srf04_data *data = iio_priv(indio_dev);
> +
> + gpiod_set_value(data->gpiod_power, 0);
> +
> + return 0;
> +}
> +
> +static int srf04_pm_runtime_resume(struct device *dev)
> +{
> + struct platform_device *pdev = container_of(dev,
> + struct platform_device, dev);
> + struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> + struct srf04_data *data = iio_priv(indio_dev);
> +
> + gpiod_set_value(data->gpiod_power, 1);
> + msleep(data->startup_time_ms);
> +
> + return 0;
> +}
> +
> +static const struct dev_pm_ops srf04_pm_ops = {
> + SET_RUNTIME_PM_OPS(srf04_pm_runtime_suspend,
> + srf04_pm_runtime_resume, NULL)
> +};
> +#endif
> +
> static struct platform_driver srf04_driver = {
> .probe = srf04_probe,
> + .remove = srf04_remove,
> .driver = {
> .name = "srf04-gpio",
> .of_match_table = of_srf04_match,
> +#ifdef CONFIG_PM
> + .pm = &srf04_pm_ops,
> +#endif
> },
> };
>
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