[media] imx074: support asynchronous probing

Both synchronous and asynchronous imx074 subdevice probing is supported by
this patch.

Signed-off-by: Guennadi Liakhovetski <[e-mail]>
Acked-by: Hans Verkuil <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/i2c/soc_camera/imx074.c

···
 #include <linux/module.h>
 
 #include <media/soc_camera.h>
+#include <media/v4l2-async.h>
 #include <media/v4l2-clk.h>
 #include <media/v4l2-subdev.h>
 
···
 	priv->fmt	= &imx074_colour_fmts[0];
 
 	priv->clk = v4l2_clk_get(&client->dev, "mclk");
-	if (IS_ERR(priv->clk))
-		return PTR_ERR(priv->clk);
+	if (IS_ERR(priv->clk)) {
+		dev_info(&client->dev, "Error %ld getting clock\n", PTR_ERR(priv->clk));
+		return -EPROBE_DEFER;
+	}
+
+	ret = soc_camera_power_init(&client->dev, ssdd);
+	if (ret < 0)
+		goto epwrinit;
 
 	ret = imx074_video_probe(client);
 	if (ret < 0)
-		v4l2_clk_put(priv->clk);
+		goto eprobe;
 
+	return v4l2_async_register_subdev(&priv->subdev);
+
+epwrinit:
+eprobe:
+	v4l2_clk_put(priv->clk);
 	return ret;
 }
 
···
 	struct soc_camera_subdev_desc *ssdd = soc_camera_i2c_to_desc(client);
 	struct imx074 *priv = to_imx074(client);
 
+	v4l2_async_unregister_subdev(&priv->subdev);
 	v4l2_clk_put(priv->clk);
+
 	if (ssdd->free_bus)
 		ssdd->free_bus(ssdd);