Re: [PATCH v9 08/13] media: rppx1: hist: Add support histogram measurement

[Jacopo Mondi]

Hi Niklas

On Sat, May 16, 2026 at 11:13:15PM +0200, Niklas Söderlund wrote:
> Extend the RPPX1 driver to allow setting the histogram 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@xxxxxxxxxxxx>
> Co-developed-by: Jai Luthra <jai.luthra+renesas@xxxxxxxxxxxxxxxx>
> Signed-off-by: Jai Luthra <jai.luthra+renesas@xxxxxxxxxxxxxxxx>
> Co-developed-by: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
> Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
> ---
> * 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     |   6 +
>  .../platform/dreamchip/rppx1/rpp_stats.c      |  10 ++
>  .../platform/dreamchip/rppx1/rppx1_hist.c     | 115 +++++++++++++++++-
>  .../uapi/linux/media/dreamchip/rppx1-config.h | 115 +++++++++++++++++-
>  5 files changed, 245 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_module.h b/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> index e968ec67b9f5..b134d140fe22 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> @@ -48,12 +48,14 @@ 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_hist_params hist;
>  	struct rppx1_exm_params exm;
>  	struct rppx1_wbmeas_params wbmeas;
>  };
>
>  union rppx1_stats_block {
>  	struct v4l2_isp_block_header header;
> +	struct rppx1_hist_stats hist;
>  	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 8c0f45e8066a..975ce3a42fb5 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> @@ -19,6 +19,9 @@ 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(HIST_PRE1, hist),
> +	RPPX1_PARAMS_BLOCK_INFO(HIST_PRE2, hist),
> +	RPPX1_PARAMS_BLOCK_INFO(HIST_POST, hist),
>  	RPPX1_PARAMS_BLOCK_INFO(EXM_PRE1, exm),
>  	RPPX1_PARAMS_BLOCK_INFO(EXM_PRE2, exm),
>  	RPPX1_PARAMS_BLOCK_INFO(WBMEAS_POST, wbmeas),
> @@ -58,6 +61,9 @@ 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_HIST_POST:
> +			module = &rpp->post.hist;
> +			break;
>  		case RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1:
>  			module = &rpp->pre1.exm;
>  			break;
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_stats.c b/drivers/media/platform/dreamchip/rppx1/rpp_stats.c
> index 388c758d805d..4c7fe611d004 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(HIST_POST, hist),
>  	RPPX1_STATS_BLOCK_INFO(EXM_PRE1, exm),
>  	RPPX1_STATS_BLOCK_INFO(WBMEAS_POST, wbmeas),
>  };
> @@ -35,6 +36,15 @@ 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_POST_HIST_MEAS) {
> +		block = rppx1_init_stats_block(rpp, stats,
> +					       RPPX1_STATS_BLOCK_TYPE_HIST_POST);
> +		if (IS_ERR(block))
> +			return;
> +
> +		rpp_module_call(&rpp->post.hist, fill_stats, block);
> +	}
> +
>  	if (isc & RPPX1_IRQ_ID_PRE1_EXM) {
>  		block = rppx1_init_stats_block(rpp, stats,
>  					       RPPX1_STATS_BLOCK_TYPE_EXM_PRE1);
> diff --git a/drivers/media/platform/dreamchip/rppx1/rppx1_hist.c b/drivers/media/platform/dreamchip/rppx1/rppx1_hist.c
> index 7c1b42e96b96..475e78b0d06a 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rppx1_hist.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rppx1_hist.c
> @@ -26,6 +26,9 @@
>
>  #define HIST_LAST_MEAS_LINE_REG			0x0010
>  #define HIST_SUBSAMPLING_REG			0x0014
> +#define HIST_SUBSAMPLING_V_STEPSIZE(x)		(((x) & 0x7f) << 24)
> +#define HIST_SUBSAMPLING_H_STEP_INC(x)		(((x) & 0x1ffff))
> +
>  #define HIST_COEFF_R_REG			0x0018
>  #define HIST_COEFF_G_REG			0x001c
>  #define HIST_COEFF_B_REG			0x0020
> @@ -49,7 +52,6 @@
>  #define HIST_FORCED_UPDATE_REG			0x0058
>  #define HIST_VSTART_STATUS_REG			0x005c
>
> -#define HIST_BIN_REG_NUM			32
>  #define HIST_BIN_REG(n)				(0x0060 + (4 * (n)))
>
>  static int rppx1_hist_probe(struct rpp_module *mod)
> @@ -72,6 +74,117 @@ static int rppx1_hist_probe(struct rpp_module *mod)
>  	return 0;
>  }
>
> +#define RPPX1_HIST_WEIGHT(v0, v1, v2, v3) \
> +	(((v0) & 0x1f) | (((v1) & 0x1f) << 8)  | \
> +	(((v2) & 0x1f) << 16) | \
> +	(((v3) & 0x1f) << 24))
> +
> +static int rppx1_hist_fill_params(struct rpp_module *mod,
> +				  const union rppx1_params_block *block,
> +				  rppx1_reg_write write, void *priv)
> +{
> +	const struct rppx1_hist_params *cfg = &block->hist;
> +	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 + HIST_MODE_REG,
> +		      HIST_MODE_HIST_MODE_DISABLE);
> +		return 0;
> +	}
> +
> +	/* Select sample point */
> +	write(priv, mod->base + HIST_CHANNEL_SEL_REG,
> +	      cfg->channel_sel & HIST_CHANNEL_SEL_CHANNEL_SELECT_MASK);
> +
> +	/*
> +	 * Configure the input subsampling.
> +	 *
> +	 * v_stepsize controls which lines are processed. In Bayer mode the
> +	 * effective value is double to account for the 2x2 macro-pixel size.

Now that I read I find the part about Bayer a bit confusing, as I
don't get if it's something the HW does automatically or userspace has
to take into account. Should we drop it ?

> +	 *
> +	 * h_step_inc is the horizontal pixel increment counter. The subsampling
> +	 * counter is incremented by h_step_inc. When the result of the
> +	 * increment overflows 2^16 a sampling is performed. In Bayer mode the
> +	 * subsampling counter is only incremented for color channels selected
> +	 * by hist_mode.

Or use the above, in a separate paragraph here.

         * In Bayer mode the vertical and horizontal subsampling
         * counters are only incremented for color channels selected
         * by hist_mode.

> +	 */
> +	write(priv, mod->base + HIST_SUBSAMPLING_REG,
> +	      HIST_SUBSAMPLING_V_STEPSIZE(cfg->v_stepsize) |
> +	      HIST_SUBSAMPLING_H_STEP_INC(cfg->h_step_inc));
> +
> +	/*
> +	 * Adjust and set measurement window to hardware limitations,
> +	 * - Offsets must be even.
> +	 * - Width and height must be divisible by 10.

Same as per the exm module I would say "even and divisible in 5
windows"

> +	 */
> +	h_offs = cfg->wnd.h_offs & 0x1ffe;
> +	v_offs = cfg->wnd.v_offs & 0x1ffe;
> +	h_size = cfg->wnd.h_size - cfg->wnd.h_size % 10;
> +	v_size = cfg->wnd.v_size - cfg->wnd.v_size % 10;
> +
> +	write(priv, mod->base + HIST_H_OFFS_REG, h_offs);
> +	write(priv, mod->base + HIST_V_OFFS_REG, v_offs);
> +	write(priv, mod->base + HIST_H_SIZE_REG, h_size / 5);
> +	write(priv, mod->base + HIST_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.

Same question as per the EXM module here. Should we ignore it ?

> +	 */
> +	write(priv, mod->base + HIST_LAST_MEAS_LINE_REG, v_offs + v_size + 1);
> +
> +	/* Set measurement window weights. */
> +	write(priv, mod->base + HIST_WEIGHT_00TO30_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[0], cfg->weights[1],
> +				cfg->weights[2], cfg->weights[3]));
> +	write(priv, mod->base + HIST_WEIGHT_40TO21_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[4], cfg->weights[5],
> +				cfg->weights[6], cfg->weights[7]));
> +	write(priv, mod->base + HIST_WEIGHT_31TO12_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[8], cfg->weights[9],
> +				cfg->weights[10], cfg->weights[11]));
> +	write(priv, mod->base + HIST_WEIGHT_22TO03_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[12], cfg->weights[13],
> +				cfg->weights[14], cfg->weights[15]));
> +	write(priv, mod->base + HIST_WEIGHT_13TO43_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[16], cfg->weights[17],
> +				cfg->weights[18], cfg->weights[19]));
> +	write(priv, mod->base + HIST_WEIGHT_04TO34_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[20], cfg->weights[21],
> +				cfg->weights[22], cfg->weights[23]));
> +	write(priv, mod->base + HIST_WEIGHT_44_REG,
> +	      RPPX1_HIST_WEIGHT(cfg->weights[24], 0, 0, 0));
> +
> +	write(priv, mod->base + HIST_MODE_REG, cfg->mode);
> +	write(priv, mod->base + HIST_COEFF_R_REG, cfg->coeff[0]);
> +	write(priv, mod->base + HIST_COEFF_G_REG, cfg->coeff[1]);
> +	write(priv, mod->base + HIST_COEFF_B_REG, cfg->coeff[2]);
> +
> +	u32 sample_reg = FIELD_PREP(HIST_SAMPLE_RANGE_SAMPLE_SHIFT_MASK,
> +				    cfg->sample_shift) |
> +			 FIELD_PREP(HIST_SAMPLE_RANGE_SAMPLE_OFFSET_MASK,
> +				    cfg->sample_offs);
> +	write(priv, mod->base + HIST_SAMPLE_RANGE_REG, sample_reg);
> +
> +	write(priv, mod->base + HIST_FORCED_UPDATE_REG, 1);
> +
> +	return 0;
> +}
> +
> +static int rppx1_hist_fill_stats(struct rpp_module *mod,
> +				 union rppx1_stats_block *block)
> +{
> +	struct rppx1_hist_stats *stats = &block->hist;
> +
> +	for (unsigned int i = 0; i < RPPX1_HIST_NUM_BINS; i++)
> +		stats->hist_bins[i] = rpp_module_read(mod, HIST_BIN_REG(i)) & 0xfffff;

I wonder if we actually need the 0xfffff mask the hardware shall
provide 20-bit values already

> +
> +	return 0;
> +}
> +
>  const struct rpp_module_ops rppx1_hist_ops = {
>  	.probe = rppx1_hist_probe,
> +	.fill_params = rppx1_hist_fill_params,
> +	.fill_stats = rppx1_hist_fill_stats,
>  };
> diff --git a/include/uapi/linux/media/dreamchip/rppx1-config.h b/include/uapi/linux/media/dreamchip/rppx1-config.h
> index dbc1e116fdf5..50aba160c6cd 100644
> --- a/include/uapi/linux/media/dreamchip/rppx1-config.h
> +++ b/include/uapi/linux/media/dreamchip/rppx1-config.h
> @@ -83,6 +83,9 @@ enum rppx1_meas_chan {
>   * @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
> + * @RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE1: PRE1 pipe Histogram Measurement
> + * @RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE2: PRE2 pipe Histogram Measurement
> + * @RPPX1_PARAMS_BLOCK_TYPE_HIST_POST: POST pipe Histogram Measurement
>   */
>  enum rppx1_params_block_type {
>  	RPPX1_PARAMS_BLOCK_TYPE_WBMEAS_POST,
> @@ -91,6 +94,9 @@ enum rppx1_params_block_type {
>  	RPPX1_PARAMS_BLOCK_TYPE_AWBG_POST,
>  	RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE1,
>  	RPPX1_PARAMS_BLOCK_TYPE_EXM_PRE2,
> +	RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE1,
> +	RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE2,
> +	RPPX1_PARAMS_BLOCK_TYPE_HIST_POST,
>  };
>
>  /**
> @@ -236,6 +242,85 @@ struct rppx1_exm_params {
>  	__u8 coeff_gb;
>  };
>
> +/* Histogram */
> +#define RPPX1_HIST_WEIGHT_GRIDS_SIZE 25
> +
> +/**
> + * enum rppx1_hist_mode - Histogram measurement mode
> + *
> + * Histogram measurement mode. Select which channel or combination of channels
> + * the histogram measurement is performed on.
> + *
> + * @RPPX1_HIST_MODE_DISABLE: histogram disabled
> + * @RPPX1_HIST_MODE_RGB_COMBINED: combined RGB histogram
> + * @RPPX1_HIST_MODE_R_HISTOGRAM: red channel histogram
> + * @RPPX1_HIST_MODE_GR_HISTOGRAM: green/red channel histogram
> + * @RPPX1_HIST_MODE_B_HISTOGRAM: blue channel histogram
> + * @RPPX1_HIST_MODE_GB_HISTOGRAM: green/blue histogram
> + */
> +enum rppx1_hist_mode {
> +	RPPX1_HIST_MODE_DISABLE,
> +	RPPX1_HIST_MODE_RGB_COMBINED,
> +	RPPX1_HIST_MODE_R_HISTOGRAM,
> +	RPPX1_HIST_MODE_GR_HISTOGRAM,
> +	RPPX1_HIST_MODE_B_HISTOGRAM,
> +	RPPX1_HIST_MODE_GB_HISTOGRAM,
> +};
> +
> +/**
> + * struct rppx1_hist_params - Histogram measurement configuration
> + *
> + * The RPP-X1 Histogram measurement unit is available on the PRE1, PRE2 and
> + * MAIN_POST pipes. Userspace selects which pipe to operate by setting the
> + * @header.type field to RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE1,
> + * RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE2 or
> + * RPPX1_PARAMS_BLOCK_TYPE_HIST_POST.
> + *
> + * The histogram measurement point is selected using the @channel field while
> + * histogram measurement mode is selected using the @mode field.
> + *
> + * Histogram measurement is performed by programming subsampling factors using
> + * the @v_stepsize and @h_step_inc fields and by weighted windowing, by
> + * programming the size of the measurement window @wnd with @weights associated
> + * to each cell of the 5x5 measurement grid. Weights are represented as 5 bits
> + * integer values ranging from 0 to 16.
> + *
> + * The @last_line fields controls when the histogram measurement completes. It
> + * is usually programmed to the value of (@wnd.v_offs + @wnd.v_size - 1).
> + *
> + * Histogram values are calculated by applying a per-color channel coefficient
> + * represented as an 8 bits unsigned Q1.7 integer value. The @sample_offs and
> + * @sample_shift fields allow to reduce the color dynamic range on which
> + * histogram data are produced.
> + *
> + * @header: block header (type = RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE1,
> + *	    type = RPPX1_PARAMS_BLOCK_TYPE_HIST_PRE2 or
> + *	    type = RPPX1_PARAMS_BLOCK_TYPE_HIST_POST)
> + * @mode: histogram measurement mode (from enum rppx1_hist_mode)
> + * @channel_sel: histogram measurement point (see enum rppx1_meas_chan)
> + * @wnd: measurement window coordinates
> + * @weights: weighting factors for each sub-window (5x5 grid)
> + * @last_line: line number for which the histogram measurement completes
> + * @v_stepsize: vertical subsampling divider, 7 bits
> + * @h_step_inc: horizontal subsampling step counter, 17 bits
> + * @coeff: R-G-B coefficients, 8 bits unsigned Q1.7
> + * @sample_offs: sample offset, 24 bits
> + * @sample_shift: sample shift, 4 bits
> + */
> +struct rppx1_hist_params {
> +	struct v4l2_isp_params_block_header header;
> +	__u8 mode;
> +	__u8 channel_sel;
> +	struct rppx1_window wnd;
> +	__u8 weights[RPPX1_HIST_WEIGHT_GRIDS_SIZE];
> +	__u32 last_line;
> +	__u32 v_stepsize;
> +	__u32 h_step_inc;
> +	__u8 coeff[3];
> +	__u32 sample_offs;
> +	__u8 sample_shift;
> +};
> +
>  /**
>   * RPPX1_PARAMS_MAX_SIZE - Maximum size of all RPP-X1 parameter blocks
>   *
> @@ -248,7 +333,10 @@ struct rppx1_exm_params {
>  	sizeof(struct rppx1_awbg_params)			+	\
>  	sizeof(struct rppx1_awbg_params)			+	\
>  	sizeof(struct rppx1_exm_params)				+	\
> -	sizeof(struct rppx1_exm_params))
> +	sizeof(struct rppx1_exm_params)				+	\
> +	sizeof(struct rppx1_hist_params)			+	\
> +	sizeof(struct rppx1_hist_params)			+	\
> +	sizeof(struct rppx1_hist_params))
>
>  /* ---------------------------------------------------------------------------
>   * Statistics Structures
> @@ -267,11 +355,17 @@ struct rppx1_exm_params {
>   * @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
> + * @RPPX1_STATS_BLOCK_TYPE_HIST_PRE1: pre-fusion pipe1 histogram
> + * @RPPX1_STATS_BLOCK_TYPE_HIST_PRE2: pre-fusion pipe2 histogram
> + * @RPPX1_STATS_BLOCK_TYPE_HIST_POST: post-fusion histogram
>   */
>  enum rppx1_stats_block_type {
>  	RPPX1_STATS_BLOCK_TYPE_WBMEAS_POST,
>  	RPPX1_STATS_BLOCK_TYPE_EXM_PRE1,
>  	RPPX1_STATS_BLOCK_TYPE_EXM_PRE2,
> +	RPPX1_STATS_BLOCK_TYPE_HIST_PRE1,
> +	RPPX1_STATS_BLOCK_TYPE_HIST_PRE2,
> +	RPPX1_STATS_BLOCK_TYPE_HIST_POST,
>  };
>
>  /**
> @@ -308,6 +402,20 @@ struct rppx1_exm_stats {
>  	__u32 exp_mean[RPPX1_EXM_NUM_WIN];
>  };
>
> +/* Histogram */
> +#define RPPX1_HIST_NUM_BINS 32
> +
> +/**
> + * struct rppx1_hist_stats - Histogram statistics
> + *
> + * @header: block header (type = RPPX1_STATS_BLOCK_TYPE_HIST_POST)
> + * @hist_bins: accumulation histogram results in unsigned 20-bit Q16.4 format
> + */
> +struct rppx1_hist_stats {
> +	struct v4l2_isp_block_header header;
> +	__u32 hist_bins[RPPX1_HIST_NUM_BINS];
> +};
> +
>  /**
>   * RPPX1_STATS_MAX_SIZE - Maximum size of all RPP-X1 statistics
>   *
> @@ -317,6 +425,9 @@ struct rppx1_exm_stats {
>  #define RPPX1_STATS_MAX_SIZE						\
>  	(sizeof(struct rppx1_wbmeas_stats)			+	\
>  	sizeof(struct rppx1_exm_stats)				+	\
> -	sizeof(struct rppx1_exm_stats))
> +	sizeof(struct rppx1_exm_stats)				+	\
> +	sizeof(struct rppx1_hist_stats)				+	\
> +	sizeof(struct rppx1_hist_stats)				+	\
> +	sizeof(struct rppx1_hist_stats))

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

Thanks
  j

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