[PATCH v4] iio: adc: rockchip_saradc: add voltage notifier so get referenced voltage once at probe

[Simon Xue <xxm@xxxxxxxxxxxxxx>]

From: David Wu <david.wu@xxxxxxxxxxxxxx>

Add voltage notifier, no need to query regulator voltage for
every saradc read, just get regulator voltage once at probe.

Signed-off-by: David Wu <david.wu@xxxxxxxxxxxxxx>
Signed-off-by: Simon Xue <xxm@xxxxxxxxxxxxxx>
Reviewed-by: Heiko Stuebner <heiko@xxxxxxxxx>
---
 drivers/iio/adc/rockchip_saradc.c | 47 ++++++++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/rockchip_saradc.c b/drivers/iio/adc/rockchip_saradc.c
index f3eb8d2e50dc..a237fe469a30 100644
--- a/drivers/iio/adc/rockchip_saradc.c
+++ b/drivers/iio/adc/rockchip_saradc.c
@@ -49,10 +49,12 @@ struct rockchip_saradc {
 	struct clk		*clk;
 	struct completion	completion;
 	struct regulator	*vref;
+	int			uv_vref;
 	struct reset_control	*reset;
 	const struct rockchip_saradc_data *data;
 	u16			last_val;
 	const struct iio_chan_spec *last_chan;
+	struct notifier_block nb;
 };
 
 static void rockchip_saradc_power_down(struct rockchip_saradc *info)
@@ -105,13 +107,7 @@ static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,
 		mutex_unlock(&indio_dev->mlock);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
-		ret = regulator_get_voltage(info->vref);
-		if (ret < 0) {
-			dev_err(&indio_dev->dev, "failed to get voltage\n");
-			return ret;
-		}
-
-		*val = ret / 1000;
+		*val = info->uv_vref / 1000;
 		*val2 = chan->scan_type.realbits;
 		return IIO_VAL_FRACTIONAL_LOG2;
 	default:
@@ -298,6 +294,26 @@ static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)
 	return IRQ_HANDLED;
 }
 
+static int rockchip_saradc_volt_notify(struct notifier_block *nb,
+						   unsigned long event,
+						   void *data)
+{
+	struct rockchip_saradc *info =
+			container_of(nb, struct rockchip_saradc, nb);
+
+	if (event & REGULATOR_EVENT_VOLTAGE_CHANGE)
+		info->uv_vref = (unsigned long)data;
+
+	return NOTIFY_OK;
+}
+
+static void rockchip_saradc_regulator_unreg_notifier(void *data)
+{
+	struct rockchip_saradc *info = data;
+
+	regulator_unregister_notifier(info->vref, &info->nb);
+}
+
 static int rockchip_saradc_probe(struct platform_device *pdev)
 {
 	struct rockchip_saradc *info = NULL;
@@ -410,6 +426,12 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = regulator_get_voltage(info->vref);
+	if (ret < 0)
+		return ret;
+
+	info->uv_vref = ret;
+
 	ret = clk_prepare_enable(info->pclk);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to enable pclk\n");
@@ -450,6 +472,17 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	info->nb.notifier_call = rockchip_saradc_volt_notify;
+	ret = regulator_register_notifier(info->vref, &info->nb);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(&pdev->dev,
+				       rockchip_saradc_regulator_unreg_notifier,
+				       info);
+	if (ret)
+		return ret;
+
 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }
 
-- 
2.25.1