[PATCH] media: ov2685: Not delay latch for gain

[PATCH] media: ov2685: Not delay latch for gain

[Shunqian Zheng]

Update the register 0x3503 to use 'no delay latch' for gain.
This makes sensor to output the first frame as normal rather
than a very dark one.

Signed-off-by: Shunqian Zheng <zhengsq@rock-chips.com>
---
 drivers/media/i2c/ov2685.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/ov2685.c b/drivers/media/i2c/ov2685.c
index 9ac702e..83c55e8 100644
--- a/drivers/media/i2c/ov2685.c
+++ b/drivers/media/i2c/ov2685.c
@@ -119,7 +119,7 @@ struct ov2685 {
 	{0x3087, 0x00},
 	{0x3501, 0x4e},
 	{0x3502, 0xe0},
-	{0x3503, 0x07},
+	{0x3503, 0x27},
 	{0x350b, 0x36},
 	{0x3600, 0xb4},
 	{0x3603, 0x35},
-- 
1.9.1

Re: [PATCH] media: ov2685: Not delay latch for gain

[Tomasz Figa]

Hi Shunqian,

On Thu, Mar 1, 2018 at 5:44 PM, Shunqian Zheng <zhengsq@rock-chips.com> wrote:
> Update the register 0x3503 to use 'no delay latch' for gain.
> This makes sensor to output the first frame as normal rather
> than a very dark one.

I'm not 100% sure on how this setting works, but wouldn't it mean that
setting the gain mid-frame would result in half of the frame having
old gain and another half new? Depending how this works, perhaps we
should set this during initial register settings, but reset after
streaming starts?

Best regards,
Tomasz

Re: [PATCH] media: ov2685: Not delay latch for gain

[Shunqian Zheng]

Hi Tomasz,


On 2018年03月01日 16:53, Tomasz Figa wrote:
> Hi Shunqian,
>
> On Thu, Mar 1, 2018 at 5:44 PM, Shunqian Zheng <zhengsq@rock-chips.com> wrote:
>> Update the register 0x3503 to use 'no delay latch' for gain.
>> This makes sensor to output the first frame as normal rather
>> than a very dark one.
> I'm not 100% sure on how this setting works, but wouldn't it mean that
> setting the gain mid-frame would result in half of the frame having
> old gain and another half new? Depending how this works, perhaps we
> should set this during initial register settings, but reset after
> streaming starts?
Thank you.

I'm not quite sure too. Then I try to change gain during capture by:
    capture_10_frames.sh & while sleep .01; do v4l2-ctl -d /dev/video4 
--set-ctrl=analogue_gain=54; sleep .01; v4l2-ctl -d /dev/video4 
--set-ctrl=analogue_gain=1024; done

The gain setting takes effect for every single frame, not in mid-frame 
from my test.

Best wishes,
- Shunqian
>
> Best regards,
> Tomasz
>
>
>

Re: [PATCH] media: ov2685: Not delay latch for gain

[Tomasz Figa]

On Thu, Mar 1, 2018 at 7:14 PM, Shunqian Zheng <zhengsq@rock-chips.com> wrote:
> Hi Tomasz,
>
>
> On 2018年03月01日 16:53, Tomasz Figa wrote:
>>
>> Hi Shunqian,
>>
>> On Thu, Mar 1, 2018 at 5:44 PM, Shunqian Zheng <zhengsq@rock-chips.com>
>> wrote:
>>>
>>> Update the register 0x3503 to use 'no delay latch' for gain.
>>> This makes sensor to output the first frame as normal rather
>>> than a very dark one.
>>
>> I'm not 100% sure on how this setting works, but wouldn't it mean that
>> setting the gain mid-frame would result in half of the frame having
>> old gain and another half new? Depending how this works, perhaps we
>> should set this during initial register settings, but reset after
>> streaming starts?
>
> Thank you.
>
> I'm not quite sure too. Then I try to change gain during capture by:
>    capture_10_frames.sh & while sleep .01; do v4l2-ctl -d /dev/video4
> --set-ctrl=analogue_gain=54; sleep .01; v4l2-ctl -d /dev/video4
> --set-ctrl=analogue_gain=1024; done
>
> The gain setting takes effect for every single frame, not in mid-frame from
> my test.

Alright. I wasn't able to confirm the exact meaning of this bit myself
unfortunately, but if that's the behavior you're seeing, we should be
fine.

Reviewed-by: Tomasz Figa <tfiga@chromium.org>

Best regards,
Tomasz