media: bcm2835-unicam: Correctly handle error states on stream on/off

On a failure in start_streaming(), the error code would not propagate to
the calling function on all conditions. This would cause the userland
caller to not know of the failure.

Additionally, clk_disable_unprepare() was called unconditionally in
stop_streaming(). This is incorrect in the cases where start_streaming()
fails, and unprepares all clocks as part of the failure cleanup. Ensure
that clk_disable_unprepare() is only called in stop_streaming() if the
clocks are in a prepared state.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>

drivers/media/platform/bcm2835/bcm2835-unicam.c

@@ -426,6 +426,8 @@ struct unicam_device {
 	struct clk *clock;
 	/* vpu clock handle */
 	struct clk *vpu_clock;
+	/* Clock status */
+	bool clocks_enabled;
 	/* V4l2 device */
 	struct v4l2_device v4l2_dev;
 	struct media_device mdev;
@@ -1724,14 +1726,14 @@ static int unicam_start_streaming(struct vb2_queue *vq, unsigned int count)
 		goto err_disable_unicam;
 	}
 
+	dev->clocks_enabled = true;
 	return 0;
 
 err_disable_unicam:
 	unicam_disable(dev);
 	clk_disable_unprepare(dev->clock);
 err_vpu_clock:
-	ret = clk_set_min_rate(dev->vpu_clock, 0);
-	if (ret)
+	if (clk_set_min_rate(dev->vpu_clock, 0))
 		unicam_err(dev, "failed to reset the VPU clock\n");
 	clk_disable_unprepare(dev->vpu_clock);
 err_pm_put:
@@ -1763,12 +1765,15 @@ static void unicam_stop_streaming(struct vb2_queue *vq)
 
 		unicam_disable(dev);
 
-		ret = clk_set_min_rate(dev->vpu_clock, 0);
-		if (ret)
-			unicam_err(dev, "failed to reset the min VPU clock\n");
+		if (dev->clocks_enabled) {
+			ret = clk_set_min_rate(dev->vpu_clock, 0);
+			if (ret)
+				unicam_err(dev, "failed to reset the min VPU clock\n");
 
-		clk_disable_unprepare(dev->vpu_clock);
-		clk_disable_unprepare(dev->clock);
+			clk_disable_unprepare(dev->vpu_clock);
+			clk_disable_unprepare(dev->clock);
+			dev->clocks_enabled = false;
+		}
 		unicam_runtime_put(dev);
 
 	} else if (node->pad_id == METADATA_PAD) {