linux-kernel - [PATCH 3.16 040/132] media: ov6650: Fix sensor possibly not detected on probe

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Message-ID: <lsq.1568989415.894816342@decadent.org.uk>
Date:   Fri, 20 Sep 2019 15:23:35 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Janusz Krzysztofik" <jmkrzyszt@...il.com>,
        "Mauro Carvalho Chehab" <mchehab+samsung@...nel.org>,
        "Sakari Ailus" <sakari.ailus@...ux.intel.com>
Subject: [PATCH 3.16 040/132] media: ov6650: Fix sensor possibly not
 detected on probe

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Janusz Krzysztofik <jmkrzyszt@...il.com>

commit 933c1320847f5ed6b61a7d10f0a948aa98ccd7b0 upstream.

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.

Tested on Amstrad Delta with now out of tree but still locally
maintained omap1_camera host driver.

Fixes: 9aea470b399d ("[media] soc-camera: switch I2C subdevice drivers to use v4l2-clk")

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>
Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/i2c/soc_camera/ov6650.c | 2 ++
 1 file changed, 2 insertions(+)

--- 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
 	if (ret < 0)
 		return ret;

+	msleep(20);
+
 	/*
 	 * check and show product ID and manufacturer ID
 	 */