Re: [PATCH 3/4] drm: Extend color correction to support 3D-CLU

Hi Laurent,

On 21/12/2020 01:57, Laurent Pinchart wrote:

From: Kieran Bingham kieran.bingham+renesas@ideasonboard.com

Extend the existing color management properties to support provision of a 3D cubic look up table, allowing for color specific adjustments.

Signed-off-by: Kieran Bingham kieran.bingham+renesas@ideasonboard.com Co-developed-by: Laurent Pinchart laurent.pinchart+renesas@ideasonboard.com Signed-off-by: Laurent Pinchart laurent.pinchart+renesas@ideasonboard.com

Again, for the updates since I created the patch:

Reviewed-by: Kieran Bingham kieran.bingham+renesas@ideasonboard.com

A bit of a question on clarifying the added documentation but I don't think it's major.

---

drivers/gpu/drm/drm_atomic_helper.c | 1 + drivers/gpu/drm/drm_atomic_state_helper.c | 3 ++ drivers/gpu/drm/drm_atomic_uapi.c | 10 ++++++ drivers/gpu/drm/drm_color_mgmt.c | 41 +++++++++++++++++++---- drivers/gpu/drm/drm_mode_config.c | 14 ++++++++ include/drm/drm_crtc.h | 9 +++++ include/drm/drm_mode_config.h | 11 ++++++ 7 files changed, 82 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index ba1507036f26..0f54897d3c8d 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -3558,6 +3558,7 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc, replaced = drm_property_replace_blob(&crtc_state->degamma_lut, NULL); replaced |= drm_property_replace_blob(&crtc_state->ctm, NULL); replaced |= drm_property_replace_blob(&crtc_state->gamma_lut, blob);

• replaced |= drm_property_replace_blob(&crtc_state->cubic_lut, NULL); crtc_state->color_mgmt_changed |= replaced;

  ret = drm_atomic_commit(state);

diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c index ddcf5c2c8e6a..61c685b50677 100644 --- a/drivers/gpu/drm/drm_atomic_state_helper.c +++ b/drivers/gpu/drm/drm_atomic_state_helper.c @@ -141,6 +141,8 @@ void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc, drm_property_blob_get(state->ctm); if (state->gamma_lut) drm_property_blob_get(state->gamma_lut);

• if (state->cubic_lut)

• drm_property_blob_get(state->cubic_lut);
  

  state->mode_changed = false; state->active_changed = false; state->planes_changed = false;

@@ -213,6 +215,7 @@ void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state) drm_property_blob_put(state->degamma_lut); drm_property_blob_put(state->ctm); drm_property_blob_put(state->gamma_lut);

• drm_property_blob_put(state->cubic_lut);

} EXPORT_SYMBOL(__drm_atomic_helper_crtc_destroy_state);

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c index 268bb69c2e2f..07229acab71c 100644 --- a/drivers/gpu/drm/drm_atomic_uapi.c +++ b/drivers/gpu/drm/drm_atomic_uapi.c @@ -471,6 +471,14 @@ static int drm_atomic_crtc_set_property(struct drm_crtc *crtc, &replaced); state->color_mgmt_changed |= replaced; return ret;

• } else if (property == config->cubic_lut_property) {

• ret = drm_atomic_replace_property_blob_from_id(dev,
  

• 			&state->cubic_lut,
  

• 			val,
  

• 			-1, sizeof(struct drm_color_lut),
  

• 			&replaced);
  

• state->color_mgmt_changed |= replaced;
  

• return ret;
  

  } else if (property == config->prop_out_fence_ptr) { s32 __user *fence_ptr = u64_to_user_ptr(val);

@@ -516,6 +524,8 @@ drm_atomic_crtc_get_property(struct drm_crtc *crtc, *val = (state->ctm) ? state->ctm->base.id : 0; else if (property == config->gamma_lut_property) *val = (state->gamma_lut) ? state->gamma_lut->base.id : 0;

• else if (property == config->cubic_lut_property)

• *val = (state->cubic_lut) ? state->cubic_lut->base.id : 0;
  

  else if (property == config->prop_out_fence_ptr) *val = 0; else if (property == crtc->scaling_filter_property)

diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c index 3bcabc2f6e0e..85bbbc8ce8e5 100644 --- a/drivers/gpu/drm/drm_color_mgmt.c +++ b/drivers/gpu/drm/drm_color_mgmt.c @@ -33,7 +33,7 @@ /**

• DOC: overview

• • Color management or color space adjustments is supported through a set of 5

• • Color management or color space adjustments is supported through a set of 7
  • properties on the &drm_crtc object. They are set up by calling
  • drm_crtc_enable_color_mgmt().

@@ -60,7 +60,7 @@

• “CTM”:
• Blob property to set the current transformation matrix (CTM) apply to
• pixel data after the lookup through the degamma LUT and before the

• • lookup through the gamma LUT. The data is interpreted as a struct

• • lookup through the cubic LUT. The data is interpreted as a struct
  • &drm_color_ctm.
  • Setting this to NULL (blob property value set to 0) means a

@@ -68,13 +68,40 @@

• boot-up state too. Drivers can access the blob for the color conversion
• matrix through &drm_crtc_state.ctm.

• • ”CUBIC_LUT”:
• • Blob property to set the cubic (3D) lookup table performing color
• • mapping after the transformation matrix and before the lookup through
• • the gamma LUT. Unlike the degamma and gamma LUTs that map color
• • components independently, the 3D LUT converts an input color to an
• • output color by indexing into the 3D table using the color components
• • as a 3D coordinate. The LUT is subsampled as 8-bit (or more) precision
• • would require too much storage space in the hardware, so the precision

This sentence is a bit confusing. What bit depth is actually used, is it mandated to a specific subsampling? Or restricted to 8-bit....

• • of the color components is reduced before the look up, and the low
• • order bits may be used to interpolate between the nearest points in 3D
• • space.
• • The data is interpreted as an array of &struct drm_color_lut elements.
• • Hardware might choose not to use the full precision of the LUT
• • elements.

Is the table already reduced precision though ?

• • Setting this to NULL (blob property value set to 0) means the output
• • color is identical to the input color. This is generally the driver
• • boot-up state too. Drivers can access this blob through
• • &drm_crtc_state.cubic_lut.
• • ”CUBIC_LUT_SIZE”:
• • Unsigned range property to give the size of the lookup table to be set
• • on the CUBIC_LUT property (the size depends on the underlying hardware).
• • If drivers support multiple LUT sizes then they should publish the
• • largest size, and sub-sample smaller sized LUTs appropriately.
• • “GAMMA_LUT”:
  • Blob property to set the gamma lookup table (LUT) mapping pixel data

• • after the transformation matrix to data sent to the connector. The
• • data is interpreted as an array of &struct drm_color_lut elements.
• • Hardware might choose not to use the full precision of the LUT elements
• • nor use all the elements of the LUT (for example the hardware might
• • choose to interpolate between LUT[0] and LUT[4]).

• • after the cubic LUT to data sent to the connector. The data is
• • interpreted as an array of &struct drm_color_lut elements. Hardware
• • might choose not to use the full precision of the LUT elements nor use
• • all the elements of the LUT (for example the hardware might choose to
• • interpolate between LUT[0] and LUT[4]).
  • Setting this to NULL (blob property value set to 0) means a
  • linear/pass-thru gamma table should be used. This is generally the

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c index f1affc1bb679..6c3324f60e7d 100644 --- a/drivers/gpu/drm/drm_mode_config.c +++ b/drivers/gpu/drm/drm_mode_config.c @@ -364,6 +364,20 @@ static int drm_mode_create_standard_properties(struct drm_device *dev) return -ENOMEM; dev->mode_config.gamma_lut_size_property = prop;

• prop = drm_property_create(dev,

• 	DRM_MODE_PROP_BLOB,
  

• 	"CUBIC_LUT", 0);
  

• if (!prop)

• return -ENOMEM;
  

• dev->mode_config.cubic_lut_property = prop;
• prop = drm_property_create_range(dev,

• 	DRM_MODE_PROP_IMMUTABLE,
  

• 	"CUBIC_LUT_SIZE", 0, UINT_MAX);
  

• if (!prop)

• return -ENOMEM;
  

• dev->mode_config.cubic_lut_size_property = prop;
• prop = drm_property_create(dev, DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB, "IN_FORMATS", 0);

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h index 5f43d64d2a07..df5cc2239adb 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -288,6 +288,15 @@ struct drm_crtc_state { */ struct drm_property_blob *gamma_lut;

• /**

• * @cubic_lut:
  

• *
  

• * Cubic Lookup table for converting pixel data. See
  

• * drm_crtc_enable_color_mgmt(). The blob (if not NULL) is a 3D array
  

• * of &struct drm_color_lut.
  

• */
  

• struct drm_property_blob *cubic_lut;
• /**
  • @target_vblank:

diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h index ab424ddd7665..8edb0094e5a7 100644 --- a/include/drm/drm_mode_config.h +++ b/include/drm/drm_mode_config.h @@ -800,6 +800,17 @@ struct drm_mode_config { */ struct drm_property *gamma_lut_size_property;

• /**

• * @cubic_lut_property: Optional CRTC property to set the 3D LUT used to
  

• * convert color spaces.
  

• */
  

• struct drm_property *cubic_lut_property;
• /**

• * @cubic_lut_size_property: Optional CRTC property for the size of the
  

• * 3D LUT as supported by the driver (read-only).
  

• */
  

• struct drm_property *cubic_lut_size_property;
• /**
  • @suggested_x_property: Optional connector property with a hint for
  • the position of the output on the host's screen.