Re: [PATCH v9 07/13] media: rppx1: exm: Add support for exposure measurement

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Niklas

On Sat, May 16, 2026 at 11:13:14PM +0200, Niklas Söderlund wrote:
> Extend the RPPX1 driver to allow setting the exposure measurement
> configuration and consuming the resulting statistics. It uses the RPPX1
> framework for parameters and its writer abstraction to allow the user to
> control how, and when, configuration is applied to the RPPX1.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> Co-developed-by: Jai Luthra <jai.luthra+renesas@ideasonboard.com>
> Signed-off-by: Jai Luthra <jai.luthra+renesas@ideasonboard.com>
> Co-developed-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
> ---
> * Changes since v8
> - Use IS_ERR to check rppx1_init_stats_block() return code.
> ---
>  .../platform/dreamchip/rppx1/rpp_module.h     |   2 +
>  .../platform/dreamchip/rppx1/rpp_params.c     |   5 +
>  .../platform/dreamchip/rppx1/rpp_stats.c      |  10 ++
>  .../platform/dreamchip/rppx1/rppx1_exm.c      |  78 ++++++++++-
>  .../uapi/linux/media/dreamchip/rppx1-config.h | 121 +++++++++++++++++-
>  5 files changed, 213 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_module.h b/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> index 0e36b717b4ef..e968ec67b9f5 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> @@ -48,11 +48,13 @@ void rpp_module_clrset(struct rpp_module *mod, u32 offset, u32 mask, u32 value);
>  union rppx1_params_block {
>  	struct v4l2_isp_block_header header;
>  	struct rppx1_awbg_params awbg;
> +	struct rppx1_exm_params exm;
>  	struct rppx1_wbmeas_params wbmeas;
>  };
>
>  union rppx1_stats_block {
>  	struct v4l2_isp_block_header header;
> +	struct rppx1_exm_stats exm;
>  	struct rppx1_wbmeas_stats wbmeas;
>  };
>
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_params.c b/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> index 17bbcf366970..8c0f45e8066a 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> @@ -19,6 +19,8 @@ static const struct v4l2_isp_params_block_type_info
>  rppx1_ext_params_blocks_info[] = {
>  	RPPX1_PARAMS_BLOCK_INFO(AWBG_PRE1, awbg),
>  	RPPX1_PARAMS_BLOCK_INFO(AWBG_PRE2, awbg),
> +	RPPX1_PARAMS_BLOCK_INFO(EXM_PRE1, exm),
> +	RPPX1_PARAMS_BLOCK_INFO(EXM_PRE2, exm),
>  	RPPX1_PARAMS_BLOCK_INFO(WBMEAS_POST, wbmeas),
>  };
>
> @@ -56,6 +58,9 @@ int rppx1_params(struct rppx1 *rpp, struct vb2_buffer *vb, size_t max_size,
>  		case RPPX1_PARAMS_BLOCK_TYPE_AWBG_PRE1:
>  			module = &rpp->pre1.awbg;
>  			break;
> +		case RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1:
> +			module = &rpp->pre1.exm;
> +			break;
>  		case RPPX1_PARAMS_BLOCK_TYPE_WBMEAS_POST:
>  			module = &rpp->post.wbmeas;
>  			break;
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_stats.c b/drivers/media/platform/dreamchip/rppx1/rpp_stats.c
> index c99ea158abcf..388c758d805d 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_stats.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_stats.c
> @@ -17,6 +17,7 @@
>
>  static const struct v4l2_isp_stats_block_type_info
>  rppx1_stats_blocks_info[] = {
> +	RPPX1_STATS_BLOCK_INFO(EXM_PRE1, exm),
>  	RPPX1_STATS_BLOCK_INFO(WBMEAS_POST, wbmeas),
>  };
>
> @@ -34,6 +35,15 @@ void rppx1_stats_fill_isr(struct rppx1 *rpp, u32 isc, void *buf)
>
>  	v4l2_isp_stats_init_buffer(stats, V4L2_ISP_VERSION_V1);
>
> +	if (isc & RPPX1_IRQ_ID_PRE1_EXM) {
> +		block = rppx1_init_stats_block(rpp, stats,
> +					       RPPX1_STATS_BLOCK_TYPE_EXM_PRE1);
> +		if (IS_ERR(block))
> +			return;
> +
> +		rpp_module_call(&rpp->pre1.exm, fill_stats, block);
> +	}
> +
>  	if (isc & RPPX1_IRQ_ID_POST_AWB_MEAS) {
>  		block = rppx1_init_stats_block(rpp, stats,
>  					       RPPX1_STATS_BLOCK_TYPE_WBMEAS_POST);
> diff --git a/drivers/media/platform/dreamchip/rppx1/rppx1_exm.c b/drivers/media/platform/dreamchip/rppx1/rppx1_exm.c
> index 10b899ba201f..1694f2b487fc 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rppx1_exm.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rppx1_exm.c
> @@ -11,10 +11,14 @@
>  #define EXM_START_REG			0x0004
>
>  #define EXM_CTRL_REG			0x0008
> +#define EXM_CTRL_EXM_AUTOSTOP		BIT(1) /* HW doc says not supported. */
>  #define EXM_CTRL_EXM_UPDATE_ENABLE	BIT(0)
>
>  #define EXM_MODE_REG			0x000c
> +
>  #define EXM_CHANNEL_SEL_REG		0x0010
> +#define EXM_CHANNEL_SEL_CHANNEL_SELECT_MASK	GENMASK(2, 0)
> +
>  #define EXM_LAST_MEAS_LINE_REG		0x0014
>  #define EXM_COEFF_R_REG			0x0018
>  #define EXM_COEFF_G_GR_REG		0x001c
> @@ -27,7 +31,6 @@
>  #define EXM_FORCED_UPD_START_LINE_REG	0x0038
>  #define EXM_VSTART_STATUS_REG		0x003c
>
> -#define EXM_MEAN_REG_NUM		25
>  #define EXM_MEAN_REG(n)			(0x0040 + (4 * (n)))

This is a bit confusing as some of the defines where there already,
some are added here but not used by this patch. Not a big deal, if you
like the incremental approach instead of introducing each block in one
go I guess this might be expected

>
>  static int rppx1_exm_probe(struct rpp_module *mod)
> @@ -47,6 +50,79 @@ static int rppx1_exm_probe(struct rpp_module *mod)
>  	return 0;
>  }
>
> +static int
> +rppx1_exm_fill_params(struct rpp_module *mod,
> +		      const union rppx1_params_block *block,
> +		      rppx1_reg_write write, void *priv)
> +{
> +	const struct rppx1_exm_params *cfg = &block->exm;
> +	u32 h_offs, v_offs, h_size, v_size;
> +
> +	/* If the modules is disabled, simply bypass it. */
> +	if (cfg->header.flags & V4L2_ISP_PARAMS_FL_BLOCK_DISABLE) {
> +		write(priv, mod->base + EXM_MODE_REG, 0);
> +		return 0;
> +	}
> +
> +	switch (cfg->mode) {
> +	case RPPX1_EXP_MEASURING_MODE_RGB:
> +	case RPPX1_EXP_MEASURING_MODE_BAYER:
> +		write(priv, mod->base + EXM_MODE_REG, cfg->mode);
> +		break;
> +	default:
> +		write(priv, mod->base + EXM_MODE_REG, 0);
> +		return 0;
> +	}
> +
> +	write(priv, mod->base + EXM_COEFF_R_REG, cfg->coeff_r);
> +	write(priv, mod->base + EXM_COEFF_G_GR_REG, cfg->coeff_g_gr);
> +	write(priv, mod->base + EXM_COEFF_GB_REG, cfg->coeff_gb);
> +	write(priv, mod->base + EXM_COEFF_B_REG, cfg->coeff_b);
> +
> +	/* Select sample point */
> +	write(priv, mod->base + EXM_CHANNEL_SEL_REG,
> +	      cfg->channel_sel & EXM_CHANNEL_SEL_CHANNEL_SELECT_MASK);
> +
> +	/*
> +	 * Adjust and set measurement window to hardware limitations,
> +	 * - Offsets must be even.
> +	 * - Width and height must be divisible by 10.

Can we say "even and divisible in 5 windows". This is not an hardware
limitation but our decision to have the driver split the measurement
area in 5 windows here instead of asking userspace to do that.

> +	 */
> +	h_offs = cfg->wnd.h_offs & 0x1ffe;
> +	v_offs = cfg->wnd.v_offs & 0x1ffe;
> +	h_size = (cfg->wnd.h_size - 1) - ((cfg->wnd.h_size - 1) % 10);
> +	v_size = (cfg->wnd.v_size - 1) - ((cfg->wnd.v_size - 1) % 10);
> +
> +	write(priv, mod->base + EXM_H_OFFS_REG, h_offs);
> +	write(priv, mod->base + EXM_V_OFFS_REG, v_offs);
> +	write(priv, mod->base + EXM_H_SIZE_REG, h_size / 5);
> +	write(priv, mod->base + EXM_V_SIZE_REG, v_size / 5);
> +
> +	/*
> +	 * Set last measurement line for ready interrupt. Ignore the value
> +	 * from the parameters as it is only useful for fast-channel switching.

Should we ignore the userspace value ? As we program the window size
here I presume we should, however it feels a bit weird accepting a
parameter and then ignoring it..

> +	 */
> +	write(priv, mod->base + EXM_LAST_MEAS_LINE_REG, v_offs + v_size + 1);
> +
> +	write(priv, mod->base + EXM_START_REG, 1);
> +
> +	return 0;
> +}
> +
> +static int rppx1_exm_fill_stats(struct rpp_module *mod,
> +				union rppx1_stats_block *block)
> +{
> +	struct rppx1_exm_stats *stats = &block->exm;
> +
> +	/* Return measurements at native hardware precision. */

I would drop this comment, everything is now at native hw precision.

> +	for (unsigned int i = 0; i < RPPX1_EXM_NUM_WIN; i++)
> +		stats->exp_mean[i] = rpp_module_read(mod, EXM_MEAN_REG(i));
> +
> +	return 0;
> +}
> +
>  const struct rpp_module_ops rppx1_exm_ops = {
>  	.probe = rppx1_exm_probe,
> +	.fill_params = rppx1_exm_fill_params,
> +	.fill_stats = rppx1_exm_fill_stats,
>  };
> diff --git a/include/uapi/linux/media/dreamchip/rppx1-config.h b/include/uapi/linux/media/dreamchip/rppx1-config.h
> index 5ed8a335c9de..dbc1e116fdf5 100644
> --- a/include/uapi/linux/media/dreamchip/rppx1-config.h
> +++ b/include/uapi/linux/media/dreamchip/rppx1-config.h
> @@ -33,6 +33,36 @@ struct rppx1_window {
>  	__u16 v_size;
>  };
>
> +/**
> + * enum rppx1_meas_chan - Measurement point for the Histogram and EXM Modules
> + *
> + * Measurement points for the RPP-X1 Histogram measurement module and Exposure
> + * measurement module.
> + *
> + * All tap points are available for the PRE1/PRE2 pipes. Only
> + * RPPX1_MEAS_CHAN_SEL4 and RPPX1_MEAS_CHAN_SEL7 are available for the
> + * MAIN_POST pipe.
> + *
> + * @RPPX1_MEAS_CHAN_SEL0: after input acquisition
> + * @RPPX1_MEAS_CHAN_SEL1: after black level subtraction
> + * @RPPX1_MEAS_CHAN_SEL2: after sensor gamma linearization
> + * @RPPX1_MEAS_CHAN_SEL3: after lens shading correction
> + * @RPPX1_MEAS_CHAN_SEL4: after auto white balance gains
> + * @RPPX1_MEAS_CHAN_SEL5: after defect pixel correction
> + * @RPPX1_MEAS_CHAN_SEL6: after denoise pre-filter
> + * @RPPX1_MEAS_CHAN_SEL7: after demosaicing
> + */
> +enum rppx1_meas_chan {
> +	RPPX1_MEAS_CHAN_SEL0,
> +	RPPX1_MEAS_CHAN_SEL1,
> +	RPPX1_MEAS_CHAN_SEL2,
> +	RPPX1_MEAS_CHAN_SEL3,
> +	RPPX1_MEAS_CHAN_SEL4,
> +	RPPX1_MEAS_CHAN_SEL5,
> +	RPPX1_MEAS_CHAN_SEL6,
> +	RPPX1_MEAS_CHAN_SEL7,
> +};
> +
>  /* ---------------------------------------------------------------------------
>   * Parameter Structures
>   *
> @@ -51,12 +81,16 @@ struct rppx1_window {
>   * @RPPX1_PARAMS_BLOCK_TYPE_AWBG_PRE1: PRE1 pipe White Balance Gains
>   * @RPPX1_PARAMS_BLOCK_TYPE_AWBG_PRE2: PRE2 White Balance Gains
>   * @RPPX1_PARAMS_BLOCK_TYPE_AWBG_POST: MAIN_POST White Balance Gains
> + * @RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1: PRE1 pipe Exposure Measurement
> + * @RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE2: PRE2 pipe Exposure Measurement
>   */
>  enum rppx1_params_block_type {
>  	RPPX1_PARAMS_BLOCK_TYPE_WBMEAS_POST,
>  	RPPX1_PARAMS_BLOCK_TYPE_AWBG_PRE1,
>  	RPPX1_PARAMS_BLOCK_TYPE_AWBG_PRE2,
>  	RPPX1_PARAMS_BLOCK_TYPE_AWBG_POST,
> +	RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1,
> +	RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE2,
>  };
>
>  /**
> @@ -144,6 +178,64 @@ struct rppx1_awbg_params {
>  	__u32 gain_green_b;
>  };
>
> +/**
> + * enum rppx1_exm_mode - Exposure measurement mode
> + *
> + * Exaposure measurement mode selection (RGB/Bayer).
> + *
> + * @RPPX1_EXP_MEASURING_MODE_DISABLED: no measurement
> + * @RPPX1_EXP_MEASURING_MODE_RGB: Y/R/G/B measurement
> + * @RPPX1_EXP_MEASURING_MODE_BAYER: Bayer RGB measurement
> + */
> +enum rppx1_exm_mode {
> +	RPPX1_EXP_MEASURING_MODE_DISABLED,
> +	RPPX1_EXP_MEASURING_MODE_RGB,
> +	RPPX1_EXP_MEASURING_MODE_BAYER,
> +};
> +
> +/**
> + * struct rppx1_exm_params - Exposure measurement configuration
> + *
> + * The RPP-X1 Exposure measurement unit is available on the PRE1 and PRE2
> + * pre-fusion pipes. Userspace selects which pipe to operate by setting
> + * the @header.type field to RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1 or
> + * RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE2.
> + *
> + * Exposure measurement is performed in the RGB or Bayer domain, according to
> + * the setting of the @mode field. The exposure measurement tap point is
> + * selected according to the value of @channel_sel.
> + *
> + * The exposure measurement is performed on an input window specified in @wnd.
> + * To each color component a programmable weight coefficient is associated.
> + * Coefficients are represented as unsigned 8 bits integer values in Q1.7 format
> + * ranging from 0 to 1.992.
> + *
> + * The @last_line fields controls when the exposure measurement completes. It
> + * is usually programmed to the value of (@wnd.v_offs + @wnd.v_size + 1).
> + *
> + * @header: block header (type = RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1 or
> + *	    type = RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE2)
> + * @mode: exposure measure mode (from enum rppx1_exm_mode)
> + * @channel_sel: exposure measurement point (see enum rppx1_meas_chan)
> + * @last_line: line number for which the exposure measurement completes
> + * @wnd: measurement window coordinates
> + * @coeff_r: coefficient for the red Bayer sample or red color channel, Q1.7
> + * @coeff_g_gr: coefficient for the green/red Bayer sample or green color channel, Q1.7
> + * @coeff_b: coefficient for the blue Bayer sample or blue color channel, Q1.7
> + * @coeff_gb: coefficient for the green/blue Bayer sample, unused in RGB mode, Q1.7
> + */
> +struct rppx1_exm_params {
> +	struct v4l2_isp_params_block_header header;
> +	__u32 mode;
> +	__u8 channel_sel;
> +	__u32 last_line;
> +	struct rppx1_window wnd;
> +	__u8 coeff_r;
> +	__u8 coeff_g_gr;
> +	__u8 coeff_b;
> +	__u8 coeff_gb;
> +};
> +
>  /**
>   * RPPX1_PARAMS_MAX_SIZE - Maximum size of all RPP-X1 parameter blocks
>   *
> @@ -154,7 +246,9 @@ struct rppx1_awbg_params {
>  	(sizeof(struct rppx1_wbmeas_params)			+	\
>  	sizeof(struct rppx1_awbg_params)			+	\
>  	sizeof(struct rppx1_awbg_params)			+	\
> -	sizeof(struct rppx1_awbg_params))
> +	sizeof(struct rppx1_awbg_params)			+	\
> +	sizeof(struct rppx1_exm_params)				+	\
> +	sizeof(struct rppx1_exm_params))
>
>  /* ---------------------------------------------------------------------------
>   * Statistics Structures
> @@ -171,9 +265,13 @@ struct rppx1_awbg_params {
>   * NOTE: Only append to the enumeration as the numbers are uAPI.
>   *
>   * @RPPX1_STATS_BLOCK_TYPE_WBMEAS_POST: post-fusion white-balance measurement
> + * @RPPX1_STATS_BLOCK_TYPE_EXM_PRE1: pre-fusion pipe1 exposure measurement
> + * @RPPX1_STATS_BLOCK_TYPE_EXM_PRE2: pre-fusion pipe2 exposure measurement
>   */
>  enum rppx1_stats_block_type {
>  	RPPX1_STATS_BLOCK_TYPE_WBMEAS_POST,
> +	RPPX1_STATS_BLOCK_TYPE_EXM_PRE1,
> +	RPPX1_STATS_BLOCK_TYPE_EXM_PRE2,
>  };
>
>  /**
> @@ -193,6 +291,23 @@ struct rppx1_wbmeas_stats {
>  	__u32 mean_cr_or_r;
>  };
>
> +/* Exposure Measurement */
> +#define RPPX1_EXM_NUM_WIN 25
> +
> +/**
> + * struct rppx1_exm_stats - Exposure measurement
> + *
> + * RPP-X1 exposure measurement calculates the mean value on 25 programmable
> + * windows on the input picture.
> + *
> + * @header: block header (type = RPPX1_STATS_BLOCK_TYPE_EXM_PRE1)
> + * @exp_mean: mean luminance values per block, up to 20-bit
> + */
> +struct rppx1_exm_stats {
> +	struct v4l2_isp_block_header header;
> +	__u32 exp_mean[RPPX1_EXM_NUM_WIN];
> +};
> +
>  /**
>   * RPPX1_STATS_MAX_SIZE - Maximum size of all RPP-X1 statistics
>   *
> @@ -200,6 +315,8 @@ struct rppx1_wbmeas_stats {
>   * multiple pipes.
>   */
>  #define RPPX1_STATS_MAX_SIZE						\
> -	(sizeof(struct rppx1_wbmeas_stats))
> +	(sizeof(struct rppx1_wbmeas_stats)			+	\
> +	sizeof(struct rppx1_exm_stats)				+	\
> +	sizeof(struct rppx1_exm_stats))

Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

Thanks
  j

>
>  #endif /* __UAPI_RPP_X1_CONFIG_H */
> --
> 2.54.0
>