iio: adc: at91: add suspend and resume callback

Add suspend/resume callback, support the pinctrl sleep state when
the system suspend as well.

Signed-off-by: Wenyou Yang <[e-mail]>
Acked-by: Ludovic Desroches <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/at91_adc.c

···
 #include <linux/iio/trigger.h>
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
+#include <linux/pinctrl/consumer.h>
 
 /* Registers */
 #define AT91_ADC_CR		0x00		/* Control Register */
···
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int at91_adc_suspend(struct device *dev)
+{
+	struct iio_dev *idev = platform_get_drvdata(to_platform_device(dev));
+	struct at91_adc_state *st = iio_priv(idev);
+
+	pinctrl_pm_select_sleep_state(dev);
+	clk_disable_unprepare(st->clk);
+
+	return 0;
+}
+
+static int at91_adc_resume(struct device *dev)
+{
+	struct iio_dev *idev = platform_get_drvdata(to_platform_device(dev));
+	struct at91_adc_state *st = iio_priv(idev);
+
+	clk_prepare_enable(st->clk);
+	pinctrl_pm_select_default_state(dev);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(at91_adc_pm_ops, at91_adc_suspend, at91_adc_resume);
+
 static struct at91_adc_caps at91sam9260_caps = {
 	.calc_startup_ticks = calc_startup_ticks_9260,
 	.num_channels = 4,
···
 	.driver = {
 		   .name = DRIVER_NAME,
 		   .of_match_table = of_match_ptr(at91_adc_dt_ids),
+		   .pm = &at91_adc_pm_ops,
 	},
 };