iio: dac: stm32: add power management support

Add support for runtime PM & sleep.
Provide pclk to regmap as registers access doesn't need full power
(e.g. regulator). Always restore HFSEL when resuming. It may get lost
depending on low power level that has been achieved.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 92 insertions, 2 deletions

diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
index cce26a3a6627..f22c1d9129b2 100644
--- a/drivers/iio/dac/stm32-dac.c
+++ b/drivers/iio/dac/stm32-dac.c
@@ -13,6 +13,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 
 #include "stm32-dac-core.h"
 
@@ -20,6 +21,8 @@
 #define STM32_DAC_CHANNEL_2		2
 #define STM32_DAC_IS_CHAN_1(ch)		((ch) & STM32_DAC_CHANNEL_1)
 
+#define STM32_DAC_AUTO_SUSPEND_DELAY_MS	2000
+
 /**
  * struct stm32_dac - private data of DAC driver
  * @common:		reference to DAC common data
@@ -49,15 +52,34 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 				      bool enable)
 {
 	struct stm32_dac *dac = iio_priv(indio_dev);
+	struct device *dev = indio_dev->dev.parent;
 	u32 msk = STM32_DAC_IS_CHAN_1(ch) ? STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;
 	u32 en = enable ? msk : 0;
 	int ret;
 
+	/* already enabled / disabled ? */
+	mutex_lock(&indio_dev->mlock);
+	ret = stm32_dac_is_enabled(indio_dev, ch);
+	if (ret < 0 || enable == !!ret) {
+		mutex_unlock(&indio_dev->mlock);
+		return ret < 0 ? ret : 0;
+	}
+
+	if (enable) {
+		ret = pm_runtime_get_sync(dev);
+		if (ret < 0) {
+			pm_runtime_put_noidle(dev);
+			mutex_unlock(&indio_dev->mlock);
+			return ret;
+		}
+	}
+
 	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
+	mutex_unlock(&indio_dev->mlock);
 	if (ret < 0) {
 		dev_err(&indio_dev->dev, "%s failed\n", en ?
 			"Enable" : "Disable");
-		return ret;
+		goto err_put_pm;
 	}
 
 	/*
@@ -68,7 +90,20 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 	if (en && dac->common->hfsel)
 		udelay(1);
 
+	if (!enable) {
+		pm_runtime_mark_last_busy(dev);
+		pm_runtime_put_autosuspend(dev);
+	}
+
 	return 0;
+
+err_put_pm:
+	if (enable) {
+		pm_runtime_mark_last_busy(dev);
+		pm_runtime_put_autosuspend(dev);
+	}
+
+	return ret;
 }
 
 static int stm32_dac_get_value(struct stm32_dac *dac, int channel, int *val)
@@ -272,6 +307,7 @@ static int stm32_dac_chan_of_init(struct iio_dev *indio_dev)
 static int stm32_dac_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
+	struct device *dev = &pdev->dev;
 	struct iio_dev *indio_dev;
 	struct stm32_dac *dac;
 	int ret;
@@ -296,9 +332,61 @@ static int stm32_dac_probe(struct platform_device *pdev)
 	if (ret < 0)
 		return ret;
 
-	return devm_iio_device_register(&pdev->dev, indio_dev);
+	/* Get stm32-dac-core PM online */
+	pm_runtime_get_noresume(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_set_autosuspend_delay(dev, STM32_DAC_AUTO_SUSPEND_DELAY_MS);
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_enable(dev);
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto err_pm_put;
+
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	return 0;
+
+err_pm_put:
+	pm_runtime_disable(dev);
+	pm_runtime_set_suspended(dev);
+	pm_runtime_put_noidle(dev);
+
+	return ret;
 }
 
+static int stm32_dac_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+
+	pm_runtime_get_sync(&pdev->dev);
+	iio_device_unregister(indio_dev);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
+
+	return 0;
+}
+
+static int __maybe_unused stm32_dac_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	int channel = indio_dev->channels[0].channel;
+	int ret;
+
+	/* Ensure DAC is disabled before suspend */
+	ret = stm32_dac_is_enabled(indio_dev, channel);
+	if (ret)
+		return ret < 0 ? ret : -EBUSY;
+
+	return pm_runtime_force_suspend(dev);
+}
+
+static const struct dev_pm_ops stm32_dac_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(stm32_dac_suspend, pm_runtime_force_resume)
+};
+
 static const struct of_device_id stm32_dac_of_match[] = {
 	{ .compatible = "st,stm32-dac", },
 	{},
@@ -307,9 +395,11 @@ MODULE_DEVICE_TABLE(of, stm32_dac_of_match);
 
 static struct platform_driver stm32_dac_driver = {
 	.probe = stm32_dac_probe,
+	.remove = stm32_dac_remove,
 	.driver = {
 		.name = "stm32-dac",
 		.of_match_table = stm32_dac_of_match,
+		.pm = &stm32_dac_pm_ops,
 	},
 };
 module_platform_driver(stm32_dac_driver);