iio: adc: rzg2l_adc: Add suspend/resume support

The Renesas RZ/G3S SoC features a power-saving mode where power to most of
the SoC components is turned off, including the ADC IP.

Suspend/resume support has been added to the rzg2l_adc driver to restore
functionality after resuming from this power-saving mode. During suspend,
the ADC resets are asserted, and the ADC is powered down. On resume, the
ADC resets are de-asserted, the hardware is re-initialized, and the ADC
power is restored using the runtime PM APIs.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://patch.msgid.link/20241206111337.726244-12-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: claudiubeznea

drivers/iio/adc/rzg2l_adc.c

@@ -88,6 +88,7 @@ struct rzg2l_adc {
 	struct completion completion;
 	struct mutex lock;
 	u16 last_val[RZG2L_ADC_MAX_CHANNELS];
+	bool was_rpm_active;
 };
 
 /**
@@ -529,8 +530,77 @@ static int rzg2l_adc_pm_runtime_resume(struct device *dev)
 	return 0;
 }
 
+static int rzg2l_adc_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct rzg2l_adc *adc = iio_priv(indio_dev);
+	struct reset_control_bulk_data resets[] = {
+		{ .rstc = adc->presetn },
+		{ .rstc = adc->adrstn },
+	};
+	int ret;
+
+	if (pm_runtime_suspended(dev)) {
+		adc->was_rpm_active = false;
+	} else {
+		ret = pm_runtime_force_suspend(dev);
+		if (ret)
+			return ret;
+		adc->was_rpm_active = true;
+	}
+
+	ret = reset_control_bulk_assert(ARRAY_SIZE(resets), resets);
+	if (ret)
+		goto rpm_restore;
+
+	return 0;
+
+rpm_restore:
+	if (adc->was_rpm_active)
+		pm_runtime_force_resume(dev);
+
+	return ret;
+}
+
+static int rzg2l_adc_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct rzg2l_adc *adc = iio_priv(indio_dev);
+	struct reset_control_bulk_data resets[] = {
+		{ .rstc = adc->adrstn },
+		{ .rstc = adc->presetn },
+	};
+	int ret;
+
+	ret = reset_control_bulk_deassert(ARRAY_SIZE(resets), resets);
+	if (ret)
+		return ret;
+
+	if (adc->was_rpm_active) {
+		ret = pm_runtime_force_resume(dev);
+		if (ret)
+			goto resets_restore;
+	}
+
+	ret = rzg2l_adc_hw_init(dev, adc);
+	if (ret)
+		goto rpm_restore;
+
+	return 0;
+
+rpm_restore:
+	if (adc->was_rpm_active) {
+		pm_runtime_mark_last_busy(dev);
+		pm_runtime_put_autosuspend(dev);
+	}
+resets_restore:
+	reset_control_bulk_assert(ARRAY_SIZE(resets), resets);
+	return ret;
+}
+
 static const struct dev_pm_ops rzg2l_adc_pm_ops = {
 	RUNTIME_PM_OPS(rzg2l_adc_pm_runtime_suspend, rzg2l_adc_pm_runtime_resume, NULL)
+	SYSTEM_SLEEP_PM_OPS(rzg2l_adc_suspend, rzg2l_adc_resume)
 };
 
 static struct platform_driver rzg2l_adc_driver = {