Re: [v8 14/14] media: rppx1: lin: Add support for gamma sensor linearization

Jacopo Mondi
2026-05-06T15:57:54Z

Hi Niklas,

On Mon, May 04, 2026 at 03:05:56AM +0200, Niklas Söderlund wrote:
> From: Jai Luthra <jai.luthra@ideasonboard.com>
>
> Extend the RPPX1 driver to allow setting the gamma sensor linearization
> configuration parameters. 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: Jai Luthra <jai.luthra@ideasonboard.com>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
> .../platform/dreamchip/rppx1/rpp_module.h | 1 +
> .../platform/dreamchip/rppx1/rpp_params.c | 5 ++
> .../platform/dreamchip/rppx1/rppx1_lin.c | 55 +++++++++++++++++++
> .../uapi/linux/media/dreamchip/rppx1-config.h | 48 +++++++++++++++-
> 4 files changed, 108 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_module.h b/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> index 136ec4d48054..27235fdfb749 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_module.h
> @@ -86,6 +86,7 @@ void rpp_module_clrset(struct rpp_module *mod, u32 offset, u32 mask, u32 value);
> union rppx1_params_block {
> struct v4l2_isp_params_block_header header;
> struct rppx1_bls_params bls;
> + struct rppx1_lin_params lin;
> struct rppx1_lsc_params lsc;
> struct rppx1_awbg_params awbg;
> struct rppx1_bd_params bd;
> diff --git a/drivers/media/platform/dreamchip/rppx1/rpp_params.c b/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> index edea25293d64..1995a80890f4 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rpp_params.c
> @@ -18,6 +18,8 @@ static const struct v4l2_isp_block_type_info
> rppx1_ext_params_blocks_info[] = {
> RPPX1_PARAMS_BLOCK_INFO(BLS_PRE1, bls),
> RPPX1_PARAMS_BLOCK_INFO(BLS_PRE2, bls),
> + RPPX1_PARAMS_BLOCK_INFO(LIN_PRE1, lin),
> + RPPX1_PARAMS_BLOCK_INFO(LIN_PRE2, lin),
> RPPX1_PARAMS_BLOCK_INFO(LSC_PRE1, lsc),
> RPPX1_PARAMS_BLOCK_INFO(LSC_PRE2, lsc),
> RPPX1_PARAMS_BLOCK_INFO(AWBG_PRE1, awbg),
> @@ -72,6 +74,9 @@ int rppx1_params(struct rppx1 *rpp, struct vb2_buffer *vb, size_t max_size,
> case RPPX1_PARAMS_BLOCK_TYPE_BLS_PRE1:
> module = &rpp->pre1.bls;
> break;
> + case RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE1:
> + module = &rpp->pre1.lin;
> + break;
> case RPPX1_PARAMS_BLOCK_TYPE_LSC_PRE1:
> module = &rpp->pre1.lsc;
> break;
> diff --git a/drivers/media/platform/dreamchip/rppx1/rppx1_lin.c b/drivers/media/platform/dreamchip/rppx1/rppx1_lin.c
> index f595f56a292e..cc8efe3b3f2c 100644
> --- a/drivers/media/platform/dreamchip/rppx1/rppx1_lin.c
> +++ b/drivers/media/platform/dreamchip/rppx1/rppx1_lin.c
> @@ -24,6 +24,11 @@
> #define LIN_B_Y_REG_NUM 17
> #define LIN_B_Y_REG(n) (0x0098 + (4 * (n)))
>
> +#define LIN_PRE1_DEGAMMA_CURVE_MASK GENMASK(23, 0)
> +#define LIN_PRE1_SAMPLE_POINTS_MASK GENMASK(3, 0)
> +#define LIN_PRE2_DEGAMMA_CURVE_MASK GENMASK(11, 0)
> +#define LIN_PRE2_SAMPLE_POINTS_MASK GENMASK(2, 0)
> +
> static int rppx1_lin_probe(struct rpp_module *mod)
> {
> /* Version check. */
> @@ -52,7 +57,57 @@ static int rppx1_lin_start(struct rpp_module *mod,
> return 0;
> }
>
> +static int rppx1_lin_fill_params(struct rpp_module *mod,
> + const union rppx1_params_block *block,
> + rppx1_reg_write write, void *priv)
> +{
> + const struct rppx1_lin_params *cfg = &block->lin;
> + u8 sample_mask;
> + u32 mask;
> +
> + if (cfg->header.flags & V4L2_ISP_PARAMS_FL_BLOCK_DISABLE) {
> + write(priv, mod->base + LIN_ENABLE_REG, 0);
> + return 0;
> + }
> +
> + switch (cfg->header.type) {
> + case RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE1:
> + mask = LIN_PRE1_DEGAMMA_CURVE_MASK;
> + sample_mask = LIN_PRE1_SAMPLE_POINTS_MASK;
> + break;
> + case RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE2:
> + mask = LIN_PRE2_DEGAMMA_CURVE_MASK;
> + sample_mask = LIN_PRE2_SAMPLE_POINTS_MASK;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + u32 dx_lo = 0;
> + u32 dx_hi = 0;

I was clearly over-excited by the modernity of C99 that allows mixing
declarations and code. However this is still a discouraged practice
unless there are good reasons to do so. Probably in this case there
aren't enough.

> +
> + for (unsigned int i = 0; i < 8; ++i) {
> + dx_lo |= (cfg->dx[i] & sample_mask) << 4 * i;
> + dx_hi |= (cfg->dx[i + 8] & sample_mask) << 4 * i;
> + }
> +
> + write(priv, mod->base + LIN_DX_LO_REG, dx_lo);
> + write(priv, mod->base + LIN_DX_HI_REG, dx_hi);
> +
> + for (unsigned int i = 0; i < RPPX1_LIN_DEGAMMA_CURVE_NUM; i++) {
> + write(priv, mod->base + LIN_R_Y_REG(i), cfg->curve_r[i] & mask);
> + write(priv, mod->base + LIN_G_Y_REG(i), cfg->curve_g[i] & mask);
> + write(priv, mod->base + LIN_B_Y_REG(i), cfg->curve_b[i] & mask);
> + }
> +
> + if ((cfg->header.flags & V4L2_ISP_PARAMS_FL_BLOCK_ENABLE))
> + write(priv, mod->base + LIN_ENABLE_REG, LIN_ENABLE_GAMMA_IN_EN);
> +
> + return 0;
> +}
> +
> const struct rpp_module_ops rppx1_lin_ops = {
> .probe = rppx1_lin_probe,
> .start = rppx1_lin_start,
> + .fill_params = rppx1_lin_fill_params,
> };
> diff --git a/include/uapi/linux/media/dreamchip/rppx1-config.h b/include/uapi/linux/media/dreamchip/rppx1-config.h
> index 0246e9af1d1d..e743e11d11e9 100644
> --- a/include/uapi/linux/media/dreamchip/rppx1-config.h
> +++ b/include/uapi/linux/media/dreamchip/rppx1-config.h
> @@ -95,6 +95,8 @@ enum rppx1_meas_chan {
> * @RPPX1_PARAMS_BLOCK_TYPE_DB_FILTER_POST: Debayer filtering
> * @RPPX1_PARAMS_BLOCK_TYPE_BD_PRE1: PRE1 pipe De-noise Pre-Filter
> * @RPPX1_PARAMS_BLOCK_TYPE_BD_PRE2: PRE2 pipe De-noise Pre-Filter
> + * @RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE1: PRE1 pipe Linearization (Sensor De-gamma)
> + * @RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE2: PRE2 pipe Linearization (Sensor De-gamma)
> */
> enum rppx1_params_block_type {
> RPPX1_PARAMS_BLOCK_TYPE_WBMEAS_POST,
> @@ -117,6 +119,8 @@ enum rppx1_params_block_type {
> RPPX1_PARAMS_BLOCK_TYPE_DB_FILTER_POST,
> RPPX1_PARAMS_BLOCK_TYPE_BD_PRE1,
> RPPX1_PARAMS_BLOCK_TYPE_BD_PRE2,
> + RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE1,
> + RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE2,
> };
>
> /**
> @@ -735,6 +739,46 @@ struct rppx1_bd_params {
> struct rppx1_bd_nll nll;
> };
>
> +/* Linearization (Sensor De-gamma) */
> +#define RPPX1_LIN_SAMPLE_POINTS_NUM 16
> +#define RPPX1_LIN_DEGAMMA_CURVE_NUM 17
> +
> +/**
> + * struct rppx1_lin_params - Linearization (Sensor De-gamma) configuration
> + *
> + * The RPP-X1 linearization module 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_LIN_PRE1 or
> + * RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE2.
> + *
> + * The LIN module applies the per-color channel de-gamma linearization curves
> + * @curve_r, @curve_g and @curve_b defined on the input sampling points @dx.
> + *
> + * For the PRE1 pipe the de-gamma curves values are 24-bits, for the PRE2 pipe
> + * the de-gamma curve values are 12-bits.
> + *
> + * For the PRE1 pipe de-gamma module sampling points @dx values are in the range
> + * [0, 15] (4 bits). For the PRE2 pipe de-gamma module sampling points values
> + * are in the range [0, 7] (3 bits).
> + *
> + * Userspace is expected to provide the curve values and sampling points with a
> + * bit-depth matching the one of pipe in use.
> + *
> + * @header: block header (type = RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE1 or
> + * RPPX1_PARAMS_BLOCK_TYPE_LIN_PRE2)
> + * @curve_r: de-gamma linearization curve for red channel
> + * @curve_g: de-gamma linearization curve for green channel
> + * @curve_b: de-gamma linearization curve for blue channel
> + * @dx: input sampling points
> + */
> +struct rppx1_lin_params {
> + struct v4l2_isp_params_block_header header;
> + __u32 curve_r[RPPX1_LIN_DEGAMMA_CURVE_NUM];
> + __u32 curve_g[RPPX1_LIN_DEGAMMA_CURVE_NUM];
> + __u32 curve_b[RPPX1_LIN_DEGAMMA_CURVE_NUM];
> + __u8 dx[RPPX1_LIN_SAMPLE_POINTS_NUM];
> +};
> +
> /**
> * RPPX1_PARAMS_MAX_SIZE - Maximum size of all RPP-X1 parameter blocks
> *
> @@ -761,7 +805,9 @@ struct rppx1_bd_params {
> sizeof(struct rppx1_db_demosaic_params) + \
> sizeof(struct rppx1_db_filter_params) + \
> sizeof(struct rppx1_bd_params) + \
> - sizeof(struct rppx1_bd_params))
> + sizeof(struct rppx1_bd_params) + \
> + sizeof(struct rppx1_lin_params) + \
> + sizeof(struct rppx1_lin_params))
>
> /* ---------------------------------------------------------------------------
> * Statistics Structures
> --
> 2.54.0
>
>