linux-kernel - Re: [PATCH] media: ov5640: Put max framerate into table and simplify check

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Date:   Mon, 16 Dec 2019 05:25:55 -0600
From:   Adam Ford <aford173@...il.com>
To:     Steve Longerbeam <slongerbeam@...il.com>
Cc:     linux-media <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: ov5640: Put max framerate into table and simplify check

On Fri, Oct 25, 2019 at 2:07 PM Adam Ford <aford173@...il.com> wrote:
>
> Currently the various modes are placed into a table, but when
> ov5640_find_mode is called, it has to double check whether
> or not the requested framerate is tolerated by the mode.
> The determination is based on checking hact, vact, and frame rate.
>
> Only 640x480 is allowed at 60fps and QSXGA is limited to 15fps, but
> as the number of permitted frame rates change, this will begin to
> add more and more complexity to the check.
>
> This patch simplifies the check by adding the max framerate
> allowed for each mode into the table of modes.  It then compares
> the requested framerate to the max permitted in the mode's table.
> This reduces the number of comparisions to one down from three
> at run-time.

Gentle nudge on this patch.  It's been nearly two months without any feedback.
There were some fixes backported to stable kernels which will get ugly
as this drivers gets more mature and as framerates start to increase.

This patch should simplify the check by adding the max frame rate to
the table and then only having to do to one check later.

adam
>
> Signed-off-by: Adam Ford <aford173@...il.com>
>
> diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> index 5e495c833d32..19e10c59860b 100644
> --- a/drivers/media/i2c/ov5640.c
> +++ b/drivers/media/i2c/ov5640.c
> @@ -189,6 +189,7 @@ struct ov5640_mode_info {
>         u32 vtot;
>         const struct reg_value *reg_data;
>         u32 reg_data_size;
> +       u32 max_fps;
>  };
>
>  struct ov5640_ctrls {
> @@ -544,6 +545,7 @@ static const struct ov5640_mode_info ov5640_mode_init_data = {
>         0, SUBSAMPLING, 640, 1896, 480, 984,
>         ov5640_init_setting_30fps_VGA,
>         ARRAY_SIZE(ov5640_init_setting_30fps_VGA),
> +       OV5640_30_FPS,
>  };
>
>  static const struct ov5640_mode_info
> @@ -551,39 +553,48 @@ ov5640_mode_data[OV5640_NUM_MODES] = {
>         {OV5640_MODE_QCIF_176_144, SUBSAMPLING,
>          176, 1896, 144, 984,
>          ov5640_setting_QCIF_176_144,
> -        ARRAY_SIZE(ov5640_setting_QCIF_176_144)},
> +        ARRAY_SIZE(ov5640_setting_QCIF_176_144),
> +        OV5640_30_FPS},
>         {OV5640_MODE_QVGA_320_240, SUBSAMPLING,
>          320, 1896, 240, 984,
>          ov5640_setting_QVGA_320_240,
> -        ARRAY_SIZE(ov5640_setting_QVGA_320_240)},
> +        ARRAY_SIZE(ov5640_setting_QVGA_320_240),
> +        OV5640_30_FPS},
>         {OV5640_MODE_VGA_640_480, SUBSAMPLING,
>          640, 1896, 480, 1080,
>          ov5640_setting_VGA_640_480,
> -        ARRAY_SIZE(ov5640_setting_VGA_640_480)},
> +        ARRAY_SIZE(ov5640_setting_VGA_640_480),
> +        OV5640_60_FPS},
>         {OV5640_MODE_NTSC_720_480, SUBSAMPLING,
>          720, 1896, 480, 984,
>          ov5640_setting_NTSC_720_480,
> -        ARRAY_SIZE(ov5640_setting_NTSC_720_480)},
> +        ARRAY_SIZE(ov5640_setting_NTSC_720_480),
> +       OV5640_30_FPS},
>         {OV5640_MODE_PAL_720_576, SUBSAMPLING,
>          720, 1896, 576, 984,
>          ov5640_setting_PAL_720_576,
> -        ARRAY_SIZE(ov5640_setting_PAL_720_576)},
> +        ARRAY_SIZE(ov5640_setting_PAL_720_576),
> +        OV5640_30_FPS},
>         {OV5640_MODE_XGA_1024_768, SUBSAMPLING,
>          1024, 1896, 768, 1080,
>          ov5640_setting_XGA_1024_768,
> -        ARRAY_SIZE(ov5640_setting_XGA_1024_768)},
> +        ARRAY_SIZE(ov5640_setting_XGA_1024_768),
> +        OV5640_30_FPS},
>         {OV5640_MODE_720P_1280_720, SUBSAMPLING,
>          1280, 1892, 720, 740,
>          ov5640_setting_720P_1280_720,
> -        ARRAY_SIZE(ov5640_setting_720P_1280_720)},
> +        ARRAY_SIZE(ov5640_setting_720P_1280_720),
> +        OV5640_30_FPS},
>         {OV5640_MODE_1080P_1920_1080, SCALING,
>          1920, 2500, 1080, 1120,
>          ov5640_setting_1080P_1920_1080,
> -        ARRAY_SIZE(ov5640_setting_1080P_1920_1080)},
> +        ARRAY_SIZE(ov5640_setting_1080P_1920_1080),
> +        OV5640_30_FPS},
>         {OV5640_MODE_QSXGA_2592_1944, SCALING,
>          2592, 2844, 1944, 1968,
>          ov5640_setting_QSXGA_2592_1944,
> -        ARRAY_SIZE(ov5640_setting_QSXGA_2592_1944)},
> +        ARRAY_SIZE(ov5640_setting_QSXGA_2592_1944),
> +        OV5640_15_FPS},
>  };
>
>  static int ov5640_init_slave_id(struct ov5640_dev *sensor)
> @@ -1606,14 +1617,8 @@ ov5640_find_mode(struct ov5640_dev *sensor, enum ov5640_frame_rate fr,
>             (!nearest && (mode->hact != width || mode->vact != height)))
>                 return NULL;
>
> -       /* Only 640x480 can operate at 60fps (for now) */
> -       if (fr == OV5640_60_FPS &&
> -           !(mode->hact == 640 && mode->vact == 480))
> -               return NULL;
> -
> -       /* 2592x1944 only works at 15fps max */
> -       if ((mode->hact == 2592 && mode->vact == 1944) &&
> -           fr > OV5640_15_FPS)
> +       /* Check to see if the current mode exceeds the max frame rate */
> +       if (ov5640_framerates[fr] > ov5640_framerates[mode->max_fps])
>                 return NULL;
>
>         return mode;
> --
> 2.17.1
>