Re: [PATCH v2 1/2] media: arm: mali-c55: Add support for CCM
From: Vincenzo Frascino
Date: Fri Jun 26 2026 - 05:45:11 EST
Hi Jacopo,
thank you for your patch!
And sorry for the delay in my review.
On 16/06/2026 15:36, Jacopo Mondi wrote:
> From: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
>
> Add support for the CCM (Color Correction Matrix) for the Mali C55 ISP.
>
> Define a new block in the uAPI using the extensible v4l2-isp format and
> implement support for configuring the CCM parameters in the mali-c55
> ISP driver.
>
> Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
I have a couple of questions. With this:
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> ---
> .../media/platform/arm/mali-c55/mali-c55-params.c | 52 ++++++++++++++++++++++
> include/uapi/linux/media/arm/mali-c55-config.h | 41 ++++++++++++++++-
> 2 files changed, 92 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-params.c b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> index de0e9d898db7..96f1b28a6d77 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> @@ -46,6 +46,7 @@
> * @awb_config: For header->type == MALI_C55_PARAM_BLOCK_AWB_CONFIG
> * @shading_config: For header->type == MALI_C55_PARAM_MESH_SHADING_CONFIG
> * @shading_selection: For header->type == MALI_C55_PARAM_MESH_SHADING_SELECTION
> + * @ccm: For header->type == MALI_C55_PARAM_BLOCK_CCM
> * @data: Allows easy initialisation of a union variable with a
> * pointer into a __u8 array.
> */
> @@ -59,6 +60,7 @@ union mali_c55_params_block {
> const struct mali_c55_params_awb_config *awb_config;
> const struct mali_c55_params_mesh_shading_config *shading_config;
> const struct mali_c55_params_mesh_shading_selection *shading_selection;
> + const struct mali_c55_params_ccm *ccm;
> const __u8 *data;
> };
>
> @@ -414,6 +416,52 @@ static void mali_c55_params_lsc_selection(struct mali_c55 *mali_c55,
> params->mesh_strength);
> }
>
> +static void mali_c55_params_ccm(struct mali_c55 *mali_c55,
> + union mali_c55_params_block block)
> +{
> + const struct mali_c55_params_ccm *params = block.ccm;
> +
> + if (block.header->flags & V4L2_ISP_PARAMS_FL_BLOCK_DISABLE) {
> + mali_c55_ctx_write(mali_c55, MALI_C55_REG_CCM_ENABLE, 0);
> + return;
> + }
> +
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_R_R,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[0][0]);
Should values be validated or masked before programming? Since this is
uAPI-controlled input, it may be worth rejecting values with bits outside
MALI_C55_CCM_COEF_MASK rather than silently truncating them in update_bits().
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_R_G,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[0][1]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_R_B,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[0][2]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_G_R,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[1][0]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_G_G,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[1][1]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_G_B,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[1][2]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_B_R,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[2][0]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_B_G,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[2][1]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_COEF_B_B,
> + MALI_C55_CCM_COEF_MASK, params->coeffs[2][2]);
> +
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_ANTIFOG_GAIN_R,
> + MALI_C55_CCM_ANTIFOG_GAIN_MASK, params->gains[0]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_ANTIFOG_GAIN_G,
> + MALI_C55_CCM_ANTIFOG_GAIN_MASK, params->gains[1]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_ANTIFOG_GAIN_B,
> + MALI_C55_CCM_ANTIFOG_GAIN_MASK, params->gains[2]);
> +
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_ANTIFOG_OFFSET_R,
> + MALI_C55_CCM_ANTIFOG_OFFSET_MASK, params->offs[0]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_ANTIFOG_OFFSET_G,
> + MALI_C55_CCM_ANTIFOG_OFFSET_MASK, params->offs[1]);
> + mali_c55_ctx_update_bits(mali_c55, MALI_C55_REG_CCM_ANTIFOG_OFFSET_B,
> + MALI_C55_CCM_ANTIFOG_OFFSET_MASK, params->offs[2]);
> +
> + mali_c55_ctx_write(mali_c55, MALI_C55_REG_CCM_ENABLE, 1);
> +}
> +
> static const mali_c55_params_handler mali_c55_params_handlers[] = {
> [MALI_C55_PARAM_BLOCK_SENSOR_OFFS] = &mali_c55_params_sensor_offs,
> [MALI_C55_PARAM_BLOCK_AEXP_HIST] = &mali_c55_params_aexp_hist,
> @@ -426,6 +474,7 @@ static const mali_c55_params_handler mali_c55_params_handlers[] = {
> [MALI_C55_PARAM_BLOCK_AWB_GAINS_AEXP] = &mali_c55_params_awb_gains,
> [MALI_C55_PARAM_MESH_SHADING_CONFIG] = &mali_c55_params_lsc_config,
> [MALI_C55_PARAM_MESH_SHADING_SELECTION] = &mali_c55_params_lsc_selection,
> + [MALI_C55_PARAM_BLOCK_CCM] = &mali_c55_params_ccm,
> };
>
> static const struct v4l2_isp_params_block_type_info
> @@ -463,6 +512,9 @@ mali_c55_params_block_types_info[] = {
> [MALI_C55_PARAM_MESH_SHADING_SELECTION] = {
> .size = sizeof(struct mali_c55_params_mesh_shading_selection),
> },
> + [MALI_C55_PARAM_BLOCK_CCM] = {
> + .size = sizeof(struct mali_c55_params_ccm),
> + },
> };
>
> static_assert(ARRAY_SIZE(mali_c55_params_handlers) ==
> diff --git a/include/uapi/linux/media/arm/mali-c55-config.h b/include/uapi/linux/media/arm/mali-c55-config.h
> index 3d335f950eeb..0b2085eed81b 100644
> --- a/include/uapi/linux/media/arm/mali-c55-config.h
> +++ b/include/uapi/linux/media/arm/mali-c55-config.h
> @@ -219,6 +219,7 @@ struct mali_c55_stats_buffer {
> * @MALI_C55_PARAM_BLOCK_AWB_GAINS_AEXP: Auto-white balance gains for AEXP-0 tap
> * @MALI_C55_PARAM_MESH_SHADING_CONFIG : Mesh shading tables configuration
> * @MALI_C55_PARAM_MESH_SHADING_SELECTION: Mesh shading table selection
> + * @MALI_C55_PARAM_BLOCK_CCM: Colour correction matrix
> */
> enum mali_c55_param_block_type {
> MALI_C55_PARAM_BLOCK_SENSOR_OFFS,
> @@ -232,6 +233,7 @@ enum mali_c55_param_block_type {
> MALI_C55_PARAM_BLOCK_AWB_GAINS_AEXP,
> MALI_C55_PARAM_MESH_SHADING_CONFIG,
> MALI_C55_PARAM_MESH_SHADING_SELECTION,
> + MALI_C55_PARAM_BLOCK_CCM,
> };
>
> /**
> @@ -757,6 +759,42 @@ struct mali_c55_params_mesh_shading_selection {
> __u16 mesh_strength;
> };
>
> +/**
> + * struct mali_c55_params_ccm - Coefficients, offsets and gains for the colour
> + * correction matrix
> + *
> + * The colour correction module converts images data from a sensor-specific
> + * colour space to known one.
> + *
> + * Colour correction is applied after demosaicing and each pixel is represented
> + * as a column vector of the three RGB colour channels on which the following
> + * operations take place:
> + * 1) An offset is subtracted from each colour channel
> + * 2) Each colour channel is multiplied by a gain
> + * 3) The pixel column vector is multiplied by the colour correction matrix
> + *
> + * This struct allows users to configure the coefficients for CCM and the
> + * per-channel offsets and gains. The nine matrix coefficients are expressed as
> + * signed Q4.8 Sign/Magnitude fixed-point numbers, the three gain multipliers
> + * are expressed as unsigned Q4.8 fixed-point numbers and the three offsets are
> + * expressed as a 12-bit unsigned integers.
> + *
> + * header.type should be set to MALI_C55_PARAM_BLOCK_CCM from
> + * :c:type:`mali_c55_param_block_type`.
> + *
> + * @header: The Mali-C55 parameters block header
> + * @coeffs: 3x3 color conversion matrix coefficients in sign/magnitude
> + * Q4.8 format
> + * @gains: Gains for red, green and blue channels in unsigned Q4.8 format
> + * @offs: Offsets for red, green and blue channels
> + */
> +struct mali_c55_params_ccm {
> + struct v4l2_isp_params_block_header header;
> + __u16 coeffs[3][3];
> + __u16 gains[3];
> + __u16 offs[3];
The comment says offsets are 12-bit unsigned integers. Is there a reason why
instead of validation in the params parser so userspace gets an error for values
above 4095, we rely on register masking?
> +};
> +
> /**
> * define MALI_C55_PARAMS_MAX_SIZE - Maximum size of all Mali C55 Parameters
> *
> @@ -780,6 +818,7 @@ struct mali_c55_params_mesh_shading_selection {
> sizeof(struct mali_c55_params_awb_config) + \
> sizeof(struct mali_c55_params_awb_gains) + \
> sizeof(struct mali_c55_params_mesh_shading_config) + \
> - sizeof(struct mali_c55_params_mesh_shading_selection))
> + sizeof(struct mali_c55_params_mesh_shading_selection) + \
> + sizeof(struct mali_c55_params_ccm))
>
> #endif /* __UAPI_MALI_C55_CONFIG_H */
>
--
Regards,
Vincenzo