linux-kernel - Re: [PATCH v3 2/3] media: i2c: imx219: make HBLANK r/w to allow longer exposures

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Message-ID: <20241126121640.GE5461@pendragon.ideasonboard.com>
Date: Tue, 26 Nov 2024 14:16:40 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Jai Luthra <jai.luthra@...asonboard.com>
Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.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 v3 2/3] media: i2c: imx219: make HBLANK r/w to allow
 longer exposures

On Mon, Nov 25, 2024 at 08:36:26PM +0530, Jai Luthra wrote:
> From: Dave Stevenson <dave.stevenson@...pberrypi.com>
> 
> The HBLANK control was read-only, and always configured such
> that the sensor HTS register was 3448. This limited the maximum
> exposure time that could be achieved to around 1.26 secs.
> 
> Make HBLANK read/write so that the line time can be extended,
> and thereby allow longer exposures (and slower frame rates).
> Retain the overall HTS setting when changing modes rather than
> resetting it to a default.
> 
> Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>
> Signed-off-by: Jai Luthra <jai.luthra@...asonboard.com>
> ---
>  drivers/media/i2c/imx219.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> index f98aad74fe584a18e2fe7126f92bf294762a54e3..970e6362d0ae3a9078daf337155e83d637bc1ca1 100644
> --- a/drivers/media/i2c/imx219.c
> +++ b/drivers/media/i2c/imx219.c
> @@ -76,8 +76,10 @@
>  
>  #define IMX219_VBLANK_MIN		32
>  
> -/* HBLANK control - read only */
> -#define IMX219_PPL_DEFAULT		3448
> +/* HBLANK control range */

Just drop the comment, and drop the blank lines, this belongs to the
"V_TIMING internal" section.

> +#define IMX219_PPL_MIN			0x0d78

Why PPL and not HTS ?

> +#define IMX219_PPL_MAX			0x7ff0
> +#define IMX219_REG_HTS			CCI_REG16(0x0162)

The min/max should go below the register definition.

>  
>  #define IMX219_REG_LINE_LENGTH_A	CCI_REG16(0x0162)
>  #define IMX219_REG_X_ADD_STA_A		CCI_REG16(0x0164)
> @@ -422,6 +424,10 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
>  		cci_write(imx219->regmap, IMX219_REG_VTS,
>  			  format->height + ctrl->val, &ret);
>  		break;
> +	case V4L2_CID_HBLANK:
> +		cci_write(imx219->regmap, IMX219_REG_HTS,
> +			  format->width + ctrl->val, &ret);
> +		break;
>  	case V4L2_CID_TEST_PATTERN_RED:
>  		cci_write(imx219->regmap, IMX219_REG_TESTP_RED,
>  			  ctrl->val, &ret);
> @@ -496,12 +502,10 @@ static int imx219_init_controls(struct imx219 *imx219)
>  					   V4L2_CID_VBLANK, IMX219_VBLANK_MIN,
>  					   IMX219_VTS_MAX - mode->height, 1,
>  					   mode->vts_def - mode->height);
> -	hblank = IMX219_PPL_DEFAULT - mode->width;
> +	hblank = IMX219_PPL_MIN - mode->width;
>  	imx219->hblank = v4l2_ctrl_new_std(ctrl_hdlr, &imx219_ctrl_ops,
>  					   V4L2_CID_HBLANK, hblank, hblank,

The minimum and maximum are identical, is this intentional ?

>  					   1, hblank);
> -	if (imx219->hblank)
> -		imx219->hblank->flags |= V4L2_CTRL_FLAG_READ_ONLY;
>  	exposure_max = mode->vts_def - 4;
>  	exposure_def = (exposure_max < IMX219_EXPOSURE_DEFAULT) ?
>  		exposure_max : IMX219_EXPOSURE_DEFAULT;
> @@ -817,6 +821,10 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  	struct v4l2_mbus_framefmt *format;
>  	struct v4l2_rect *crop;
>  	unsigned int bin_h, bin_v;
> +	u32 prev_hts;
> +
> +	format = v4l2_subdev_state_get_format(state, 0);
> +	prev_hts = format->width + imx219->hblank->val;
>  
>  	mode = v4l2_find_nearest_size(supported_modes,
>  				      ARRAY_SIZE(supported_modes),
> @@ -824,8 +832,6 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  				      fmt->format.width, fmt->format.height);
>  
>  	imx219_update_pad_format(imx219, mode, &fmt->format, fmt->format.code);
> -
> -	format = v4l2_subdev_state_get_format(state, 0);
>  	*format = fmt->format;
>  
>  	/*
> @@ -861,13 +867,18 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  					 exposure_max, imx219->exposure->step,
>  					 exposure_def);
>  		/*
> -		 * Currently PPL is fixed to IMX219_PPL_DEFAULT, so hblank
> -		 * depends on mode->width only, and is not changeble in any
> -		 * way other than changing the mode.
> +		 * Retain PPL setting from previous mode so that the

Rename PPL to HTS here too.

> +		 * line time does not change on a mode change.
> +		 * Limits have to be recomputed as the controls define
> +		 * the blanking only, so PPL values need to have the
> +		 * mode width subtracted.
>  		 */
> -		hblank = IMX219_PPL_DEFAULT - mode->width;
> -		__v4l2_ctrl_modify_range(imx219->hblank, hblank, hblank, 1,
> -					 hblank);
> +		hblank = prev_hts - mode->width;
> +		__v4l2_ctrl_modify_range(imx219->hblank,
> +					 IMX219_PPL_MIN - mode->width,
> +					 IMX219_PPL_MAX - mode->width,
> +					 1, IMX219_PPL_MIN - mode->width);
> +		__v4l2_ctrl_s_ctrl(imx219->hblank, hblank);
>  	}
>  
>  	return 0;
> 

-- 
Regards,

Laurent Pinchart