[BACKPORT v3.18] media: ov6650: Fix sensor possibly not detected on probe

[Janusz Krzysztofik <jmkrzyszt@gmail.com>]

After removal of clock_start() from before soc_camera_init_i2c() in
soc_camera_probe() by commit 9aea470b399d ("[media] soc-camera: switch
I2C subdevice drivers to use v4l2-clk") introduced in v3.11, the ov6650
driver could no longer probe the sensor successfully because its clock
was no longer turned on in advance.  The issue was initially worked
around by adding that missing clock_start() equivalent to OMAP1 camera
interface driver - the only user of this sensor - but a propoer fix
should be rather implemented in the sensor driver code itself.

Fix the issue by inserting a delay between the clock is turned on and
the sensor I2C registers are read for the first time.

Fixes: 9aea470b399d ("[media] soc-camera: switch I2C subdevice drivers to use v4l2-clk")
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Cc: stable@vger.kernel.org
---
Rebased on 3.18, should apply cleanly on 4.4 and 4.9 as well.

I dropped the comment on the patch being tested on an out of tree
omap1_camera driver mainly because that driver is still in the tree
in those kernel versions.

 drivers/media/i2c/soc_camera/ov6650.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/i2c/soc_camera/ov6650.c b/drivers/media/i2c/soc_camera/ov6650.c
index ab01598ec83f..c0e25bf55fb8 100644
--- a/drivers/media/i2c/soc_camera/ov6650.c
+++ b/drivers/media/i2c/soc_camera/ov6650.c
@@ -829,6 +829,8 @@ static int ov6650_video_probe(struct i2c_client *client)
 	if (ret < 0)
 		return ret;
 
+	msleep(20);
+
 	/*
 	 * check and show product ID and manufacturer ID
 	 */
-- 
2.19.2