linux-kernel - [PATCH 3.16 064/134] [media] ov2640: fix vflip control

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Message-ID: <lsq.1503062000.249884553@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Mauro Carvalho Chehab" <mchehab@...pensource.com>,
        "Frank Schaefer" <fschaefer.oss@...glemail.com>
Subject: [PATCH 3.16 064/134] [media] ov2640: fix vflip control

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

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

From: Frank Schaefer <fschaefer.oss@...glemail.com>

commit 7f140fc2064bcd23e0490d8210650e2ef21c1c89 upstream.

Enabling vflip currently causes wrong colors.
It seems that (at least with the current sensor setup) REG04_VFLIP_IMG only
changes the vertical readout direction.
Because pixels are arranged RGRG... in odd lines and GBGB... in even lines,
either a one line shift or even/odd line swap is required, too, but
apparently this doesn't happen.

I finally figured out that this can be done manually by setting
REG04_VREF_EN.
Looking at hflip, it turns out that bit REG04_HREF_EN is set there
permanetly, but according to my tests has no effect on the pixel readout
order.
So my conclusion is that the current documentation of sensor register 0x04
is wrong (has changed after preliminary datasheet version 2.2).

I'm pretty sure that automatic vertical line shift/switch can be enabled,
too, but until anyone finds ot how this works, we have to stick with manual
switching.

Signed-off-by: Frank Schäfer <fschaefer.oss@...glemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/i2c/soc_camera/ov2640.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/media/i2c/soc_camera/ov2640.c
+++ b/drivers/media/i2c/soc_camera/ov2640.c
@@ -713,8 +713,10 @@ static int ov2640_s_ctrl(struct v4l2_ctr

 	switch (ctrl->id) {
 	case V4L2_CID_VFLIP:
-		val = ctrl->val ? REG04_VFLIP_IMG : 0x00;
-		return ov2640_mask_set(client, REG04, REG04_VFLIP_IMG, val);
+		val = ctrl->val ? REG04_VFLIP_IMG | REG04_VREF_EN : 0x00;
+		return ov2640_mask_set(client, REG04,
+				       REG04_VFLIP_IMG | REG04_VREF_EN, val);
+		/* NOTE: REG04_VREF_EN: 1 line shift / even/odd line swap */
 	case V4L2_CID_HFLIP:
 		val = ctrl->val ? REG04_HFLIP_IMG : 0x00;
 		return ov2640_mask_set(client, REG04, REG04_HFLIP_IMG, val);