linux-kernel - [PATCH v3 1/2] media: i2c: OV5647: ensure clock lane in LP-11 state before streaming on

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Message-Id: <20171001102238.21585-1-jacob-chen@iotwrt.com>
Date:   Sun,  1 Oct 2017 18:22:37 +0800
From:   Jacob Chen <jacob-chen@...wrt.com>
To:     linux-media@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mchehab@...nel.org,
        vladimir_zapolskiy@...tor.com, hans.verkuil@...co.com,
        sakari.ailus@...ux.intel.com, lolivei@...opsys.com,
        p.zabel@...gutronix.de, Jacob Chen <jacob-chen@...wrt.com>
Subject: [PATCH v3 1/2] media: i2c: OV5647: ensure clock lane in LP-11 state before streaming on

When I was supporting Rpi Camera Module on the ASUS Tinker board,
I found this driver have some issues with rockchip's mipi-csi driver.
It didn't place clock lane in LP-11 state before performing
D-PHY initialisation.

>From our experience, on some OV sensors,
LP-11 state is not achieved while BIT(5)-0x4800 is cleared.

So let's set BIT(5) and BIT(0) both while not streaming, in order to
coax the clock lane into LP-11 state.

0x4800 : MIPI CTRL 00
	BIT(5) : clock lane gate enable
		0: continuous
		1: none-continuous
	BIT(0) : manually set clock lane
		0: Not used
		1: used

Signed-off-by: Jacob Chen <jacob-chen@...wrt.com>
---
 drivers/media/i2c/ov5647.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
index 95ce90fdb876..247302d01f53 100644
--- a/drivers/media/i2c/ov5647.c
+++ b/drivers/media/i2c/ov5647.c
@@ -253,6 +253,10 @@ static int ov5647_stream_on(struct v4l2_subdev *sd)
 {
 	int ret;
 
+	ret = ov5647_write(sd, 0x4800, 0x04);
+	if (ret < 0)
+		return ret;
+
 	ret = ov5647_write(sd, 0x4202, 0x00);
 	if (ret < 0)
 		return ret;
@@ -264,6 +268,10 @@ static int ov5647_stream_off(struct v4l2_subdev *sd)
 {
 	int ret;
 
+	ret = ov5647_write(sd, 0x4800, 0x25);
+	if (ret < 0)
+		return ret;
+
 	ret = ov5647_write(sd, 0x4202, 0x0f);
 	if (ret < 0)
 		return ret;
@@ -320,7 +328,10 @@ static int __sensor_init(struct v4l2_subdev *sd)
 			return ret;
 	}
 
-	return ov5647_write(sd, 0x4800, 0x04);
+	/*
+	 * stream off to make the clock lane into LP-11 state.
+	 */
+	return ov5647_stream_off(sd);
 }
 
 static int ov5647_sensor_power(struct v4l2_subdev *sd, int on)
-- 
2.14.1