linux-kernel - Re: [PATCH 1/3] media: i2c: imx219: Only use higher LLP

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Message-ID: <mloobyyocd5f4hbkenplebwyffacdjjhzhxefvlx2og5qz5xlx@zswcyzzfcpy3>
Date: Fri, 21 Feb 2025 10:28:40 +0100
From: Jacopo Mondi <jacopo.mondi@...asonboard.com>
To: Jai Luthra <jai.luthra@...asonboard.com>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Dave Stevenson <dave.stevenson@...pberrypi.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jacopo Mondi <jacopo.mondi@...asonboard.com>
Subject: Re: [PATCH 1/3] media: i2c: imx219: Only use higher LLP_MIN for
 binned resolutions

Hi Jai

On Wed, Feb 19, 2025 at 05:16:43PM +0530, Jai Luthra wrote:
> The LLP_MIN of 3560 is only needed to fix artefacts seen with binned
> resolutions. As increasing the LLP reduces the highest possible
> framerate by ~3%, use the default minimum of 3448 for non-binned
> resolutions.
>

Also restore the fll_def value for non-binned modes in the modes definition
to restore the default mode framerate to 30fps.

> Suggested-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> Link: https://lore.kernel.org/linux-media/CAPY8ntC1-S6zKtDvmc6EgyxP+j6rTShuG8Dr8PKb9XQr2PeS_w@mail.gmail.com/
> Signed-off-by: Jai Luthra <jai.luthra@...asonboard.com>
> ---
>  drivers/media/i2c/imx219.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> index f662c9d755114265aad46c5cc7f5031b9bc0dbba..6e51a7af5e2a05cacefb201d96a9fbdc349f17d8 100644
> --- a/drivers/media/i2c/imx219.c
> +++ b/drivers/media/i2c/imx219.c
> @@ -74,7 +74,8 @@
>  #define IMX219_FLL_MAX			0xffff
>  #define IMX219_VBLANK_MIN		32
>  #define IMX219_REG_LINE_LENGTH_A	CCI_REG16(0x0162)
> -#define IMX219_LLP_MIN			0x0de8
> +#define IMX219_LLP_MIN			0x0d78
> +#define IMX219_BINNED_LLP_MIN		0x0de8
>  #define IMX219_LLP_MAX			0x7ff0
>
>  #define IMX219_REG_X_ADD_STA_A		CCI_REG16(0x0164)
> @@ -317,13 +318,13 @@ static const struct imx219_mode supported_modes[] = {
>  		/* 8MPix 15fps mode */
>  		.width = 3280,
>  		.height = 2464,
> -		.fll_def = 3415,
> +		.fll_def = 3526,
>  	},
>  	{
>  		/* 1080P 30fps cropped */
>  		.width = 1920,
>  		.height = 1080,
> -		.fll_def = 1707,
> +		.fll_def = 1763,
>  	},
>  	{
>  		/* 2x2 binned 60fps mode */
> @@ -901,7 +902,7 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  	if (fmt->which == V4L2_SUBDEV_FORMAT_ACTIVE) {
>  		int exposure_max;
>  		int exposure_def;
> -		int hblank;
> +		int hblank, llp_min;
>  		int pixel_rate;
>
>  		/* Update limits and set FPS to default */
> @@ -918,6 +919,17 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  					 imx219->exposure->minimum,
>  					 exposure_max, imx219->exposure->step,
>  					 exposure_def);
> +
> +		/*
> +		 * With analog binning the default minimum line length of 3448
> +		 * can cause artefacts because the ADC operates on two lines
> +		 * together. Switch to higher minimum of 3560 if we are binning.
> +		 */
> +		llp_min = (bin_h || bin_v) ? IMX219_BINNED_LLP_MIN :

As you know, this is always true.

> +					     IMX219_LLP_MIN;
> +		__v4l2_ctrl_modify_range(imx219->hblank, llp_min - mode->width,
> +					 IMX219_LLP_MAX - mode->width, 1,
> +					 llp_min - mode->width);
>  		/*
>  		 * Retain PPL setting from previous mode so that the
>  		 * line time does not change on a mode change.
> @@ -926,10 +938,6 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  		 * mode width subtracted.
>  		 */
>  		hblank = prev_line_len - mode->width;
> -		__v4l2_ctrl_modify_range(imx219->hblank,
> -					 IMX219_LLP_MIN - mode->width,
> -					 IMX219_LLP_MAX - mode->width, 1,
> -					 IMX219_LLP_MIN - mode->width);
>  		__v4l2_ctrl_s_ctrl(imx219->hblank, hblank);
>
>  		/* Scale the pixel rate based on the mode specific factor */
>
> --
> 2.48.1
>