iio: multiplexer: iio-mux: Support settle-time-us property

If the devicetree specifies that the hardware requires a settle time,
pass this time on to the mux APIs.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20211007134641.13417-4-vincent.whitchurch@axis.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/multiplexer/iio-mux.c

@@ -33,6 +33,7 @@ struct mux {
 	struct iio_chan_spec *chan;
 	struct iio_chan_spec_ext_info *ext_info;
 	struct mux_child *child;
+	u32 delay_us;
 };
 
 static int iio_mux_select(struct mux *mux, int idx)
@@ -42,7 +43,8 @@ static int iio_mux_select(struct mux *mux, int idx)
 	int ret;
 	int i;
 
-	ret = mux_control_select(mux->control, chan->channel);
+	ret = mux_control_select_delay(mux->control, chan->channel,
+				       mux->delay_us);
 	if (ret < 0) {
 		mux->cached_state = -1;
 		return ret;
@@ -392,6 +394,9 @@ static int mux_probe(struct platform_device *pdev)
 	mux->parent = parent;
 	mux->cached_state = -1;
 
+	mux->delay_us = 0;
+	of_property_read_u32(np, "settle-time-us", &mux->delay_us);
+
 	indio_dev->name = dev_name(dev);
 	indio_dev->info = &mux_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;