linux-kernel - Re: [PATCH 0/3] Handling of reduced FPS in V4L2

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Message-ID: <1939bd77-a74d-3ad6-06db-2b1eaa205aca@synopsys.com>
Date:   Fri, 24 Mar 2017 11:03:15 +0000
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     <linux-media@...r.kernel.org>
CC:     Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] Handling of reduced FPS in V4L2

Hi Hans,


On 21-03-2017 11:49, Jose Abreu wrote:
> Hi all,
>
> This is a follow up patch from this discussion [1]. It should be
> seen more as a starting point to introduce better handling of
> time per frame in v4l2. Quoting Hans Verkuil from [1]:
>
> 1) "Add a flag V4L2_DV_FL_CAN_DETECT_REDUCED_FPS. If set,
> then the hw can detect the difference between regular fps
> and 1000/1001 fps. Note: this is only valid for timings of
> VIC codes with the V4L2_DV_FL_CAN_REDUCE_FPS flag set."
>
> 2) "Allow V4L2_DV_FL_REDUCED_FPS to be used for receivers
> if V4L2_DV_FL_CAN_DETECT_REDUCED_FPS is set."
>
> 3) "For standard VIC codes the pixelclock returned by
> query_dv_timings is that of the corresponding VIC timing,
> not what is measured. This will ensure fixed fps values"
>
> 4) "g_parm should calculate the fps based on the v4l2_bt_timings
> struct, looking at the REDUCES_FPS flags. For those receivers that
> cannot detect the difference, the fps will be 24/30/60 Hz, for
> those that can detect the difference g_parm can check if both
> V4L2_DV_FL_CAN_DETECT_REDUCED_FPS and V4L2_DV_FL_REDUCED_FPS are
> set and reduce the fps by 1000/1001."
>
> -----------
> In terms of implementation:
> 	- Point 1) is done in patch 1/3
> 	- Point 2) and 3) should be done by a HDMI Receiver driver
> 	(I think?).
> 	- Point 4) is done in patch 2/3.
> 	- The patch 3/3 is a simple implementation (which was not
> 	tested) in the cobalt driver
> -----------
> 	
> [1] https://patchwork.kernel.org/patch/9609441/
>
> Best regards,
> Jose Miguel Abreu
>
> Cc: Carlos Palminha <palminha@...opsys.com>
> Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
> Cc: Hans Verkuil <hans.verkuil@...co.com>
> Cc: linux-media@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
>
> Jose Abreu (3):
>   [media] videodev2.h: Add new DV flag CAN_DETECT_REDUCED_FPS
>   [media] v4l2-dv-timings: Introduce v4l2_calc_timeperframe helper
>   [media] cobalt: Use v4l2_calc_timeperframe helper
>
>  drivers/media/pci/cobalt/cobalt-v4l2.c    |  9 +++++--
>  drivers/media/v4l2-core/v4l2-dv-timings.c | 39 +++++++++++++++++++++++++++++++
>  include/media/v4l2-dv-timings.h           | 11 +++++++++
>  include/uapi/linux/videodev2.h            |  7 ++++++
>  4 files changed, 64 insertions(+), 2 deletions(-)
>

Can you please review this series, when possible? And if you
could test it on cobalt it would be great :)

Best regards,
Jose Miguel Abreu