Re: [PATCH v2 07/34] drm/amd/display: explicitly define EOTF and inverse EOTF
From: Melissa Wen
Date: Fri Sep 08 2023 - 10:15:01 EST
On 09/06, Harry Wentland wrote:
>
>
> On 2023-08-25 10:18, Melissa Wen wrote:
> > On 08/22, Pekka Paalanen wrote:
> >> On Thu, 10 Aug 2023 15:02:47 -0100
> >> Melissa Wen <mwen@xxxxxxxxxx> wrote:
> >>
> >>> Instead of relying on color block names to get the transfer function
> >>> intention regarding encoding pixel's luminance, define supported
> >>> Electro-Optical Transfer Functions (EOTFs) and inverse EOTFs, that
> >>> includes pure gamma or standardized transfer functions.
> >>>
> >>> Suggested-by: Harry Wentland <harry.wentland@xxxxxxx>
> >>> Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx>
> >>> ---
> >>> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 19 +++--
> >>> .../amd/display/amdgpu_dm/amdgpu_dm_color.c | 69 +++++++++++++++----
> >>> 2 files changed, 67 insertions(+), 21 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> >>> index c749c9cb3d94..f6251ed89684 100644
> >>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> >>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> >>> @@ -718,14 +718,21 @@ extern const struct amdgpu_ip_block_version dm_ip_block;
> >>>
> >>> enum amdgpu_transfer_function {
> >>> AMDGPU_TRANSFER_FUNCTION_DEFAULT,
> >>> - AMDGPU_TRANSFER_FUNCTION_SRGB,
> >>> - AMDGPU_TRANSFER_FUNCTION_BT709,
> >>> - AMDGPU_TRANSFER_FUNCTION_PQ,
> >>> + AMDGPU_TRANSFER_FUNCTION_SRGB_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_BT709_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_PQ_EOTF,
> >>> AMDGPU_TRANSFER_FUNCTION_LINEAR,
> >>> AMDGPU_TRANSFER_FUNCTION_UNITY,
> >>> - AMDGPU_TRANSFER_FUNCTION_GAMMA22,
> >>> - AMDGPU_TRANSFER_FUNCTION_GAMMA24,
> >>> - AMDGPU_TRANSFER_FUNCTION_GAMMA26,
> >>> + AMDGPU_TRANSFER_FUNCTION_GAMMA22_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_GAMMA24_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_GAMMA26_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_SRGB_INV_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_BT709_INV_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_PQ_INV_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_GAMMA22_INV_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_GAMMA24_INV_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_GAMMA26_INV_EOTF,
> >>> + AMDGPU_TRANSFER_FUNCTION_COUNT
> >>> };
> >>>
> >>> struct dm_plane_state {
> >>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
> >>> index 56ce008b9095..cc2187c0879a 100644
> >>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
> >>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
> >>> @@ -85,18 +85,59 @@ void amdgpu_dm_init_color_mod(void)
> >>> }
> >>>
> >>> #ifdef AMD_PRIVATE_COLOR
> >>> -static const struct drm_prop_enum_list amdgpu_transfer_function_enum_list[] = {
> >>> - { AMDGPU_TRANSFER_FUNCTION_DEFAULT, "Default" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_SRGB, "sRGB" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_BT709, "BT.709" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_PQ, "PQ (Perceptual Quantizer)" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_LINEAR, "Linear" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_UNITY, "Unity" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_GAMMA22, "Gamma 2.2" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_GAMMA24, "Gamma 2.4" },
> >>> - { AMDGPU_TRANSFER_FUNCTION_GAMMA26, "Gamma 2.6" },
> >>> +static const char * const
> >>> +amdgpu_transfer_function_names[] = {
> >>> + [AMDGPU_TRANSFER_FUNCTION_DEFAULT] = "Default",
> >>> + [AMDGPU_TRANSFER_FUNCTION_LINEAR] = "Linear",
> >>
> >> Hi,
> >>
> >> if the below is identity, then what is linear? Is there a coefficient
> >> (multiplier) somewhere? Offset?
> >>
> >>> + [AMDGPU_TRANSFER_FUNCTION_UNITY] = "Unity",
> >>
> >> Should "Unity" be called "Identity"?
> >
> > AFAIU, AMD treats Linear and Unity as the same: Identity. So, IIUC,
> > indeed merging both as identity sounds the best approach.
>
> Agreed.
>
> >>
> >> Doesn't unity mean that the output is always 1.0 regardless of input?
> >>
> >>> + [AMDGPU_TRANSFER_FUNCTION_SRGB_EOTF] = "sRGB EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_BT709_EOTF] = "BT.709 EOTF",
> >>
> >> BT.709 says about "Overall opto-electronic transfer characteristics at
> >> source":
> >>
> >> In typical production practice the encoding function of image
> >> sources is adjusted so that the final picture has the desired
> >> look, as viewed on a reference monitor having the reference
> >> decoding function of Recommendation ITU-R BT.1886, in the
> >> reference viewing environment defined in Recommendation ITU-R
> >> BT.2035.
> >>
> >> IOW, typically people tweak the encoding function instead of using
> >> BT.709 OETF as is, which means that inverting the BT.709 OETF produces
> >> something slightly unknown. The note about BT.1886 means that that
> >> something is also not quite how it's supposed to be turned into light.
> >>
> >> Should this enum item be "BT.709 inverse OETF" and respectively below a
> >> "BT.709 OETF"?
> >>
> >> What curve does the hardware actually implement?
> >
> > Hmmmm.. I think I got confused in using OETF here since it's done within
> > a camera. Looking at the coefficients used by AMD color module when not
> > using ROM but build encoding and decoding curves[1] on pre-defined TF
> > setup, I understand it's using OETF parameters for building both sRGB
> > and BT 709:
> >
> > ```
> > /*sRGB 709 2.2 2.4 P3*/
> > static const int32_t numerator01[] = { 31308, 180000, 0, 0, 0};
> > static const int32_t numerator02[] = { 12920, 4500, 0, 0, 0};
> > static const int32_t numerator03[] = { 55, 99, 0, 0, 0};
> > static const int32_t numerator04[] = { 55, 99, 0, 0, 0};
> > static const int32_t numerator05[] = { 2400, 2222, 2200, 2400, 2600};
> > ```
> >
>
> The first column here looks like the sRGB coefficients in Skia:
> https://skia.googlesource.com/skia/+/19936eb1b23fef5187b07fb2e0e67dcf605c0672/include/core/SkColorSpace.h#46
>
> The color module uses the same coefficients to calculate the transform
> to linear space and from linear space. So it would support a TF and its
> inverse.
>
> From what I understand for sRGB and PQ its the EOTF and its inverse.
>
> For BT.709 we should probably call it BT.709 inverse OETF (instead of
> EOTF) and BT.709 OETF (instead of inverse EOTF).
I see. I'll update the transfer function list and docs accordingly.
Thanks
Melissa
>
> While I'm okay to move ahead with these AMD driver-specific properties
> without IGT tests (since they're not enabled and not UABI) we really
> need IGT tests once they become UABI with the Color Pipeline API. And we
> need more than just CRC testing. We'll need to do pixel-by-pixel comparison
> so we can verify that the KMS driver behaves exactly how we expect for a
> large range of values.
>
> Harry
>
> > Then EOTF and inverse EOTF for PQ [2], and OETF and it seems an inverse
> > OETF but called EOTF for HLG[3]. But I'm an external dev, better if
> > Harry can confirm.
> >
> > Thank you for pointing it out.
> >
> > [1] https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/amd/display/modules/color/color_gamma.c#n55
> > [2] https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/amd/display/modules/color/color_gamma.c#n106
> > [3] https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/amd/display/modules/color/color_gamma.c#n174
> >
> >>
> >> The others seem fine to me.
> >>
> >>
> >> Thanks,
> >> pq
> >>
> >>> + [AMDGPU_TRANSFER_FUNCTION_PQ_EOTF] = "PQ EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_GAMMA22_EOTF] = "Gamma 2.2 EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_GAMMA24_EOTF] = "Gamma 2.4 EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_GAMMA26_EOTF] = "Gamma 2.6 EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_SRGB_INV_EOTF] = "sRGB inv_EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_BT709_INV_EOTF] = "BT.709 inv_EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_PQ_INV_EOTF] = "PQ inv_EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_GAMMA22_INV_EOTF] = "Gamma 2.2 inv_EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_GAMMA24_INV_EOTF] = "Gamma 2.4 inv_EOTF",
> >>> + [AMDGPU_TRANSFER_FUNCTION_GAMMA26_INV_EOTF] = "Gamma 2.6 inv_EOTF",
> >>> };
> >>>
> >>> +static const u32 amdgpu_eotf =
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_SRGB_EOTF) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_BT709_EOTF) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_PQ_EOTF) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_GAMMA22_EOTF) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_GAMMA24_EOTF) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_GAMMA26_EOTF);
> >>> +
> >>> +static struct drm_property *
> >>> +amdgpu_create_tf_property(struct drm_device *dev,
> >>> + const char *name,
> >>> + u32 supported_tf)
> >>> +{
> >>> + u32 transfer_functions = supported_tf |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_DEFAULT) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_LINEAR) |
> >>> + BIT(AMDGPU_TRANSFER_FUNCTION_UNITY);
> >>> + struct drm_prop_enum_list enum_list[AMDGPU_TRANSFER_FUNCTION_COUNT];
> >>> + int i, len;
> >>> +
> >>> + len = 0;
> >>> + for (i = 0; i < AMDGPU_TRANSFER_FUNCTION_COUNT; i++) {
> >>> + if ((transfer_functions & BIT(i)) == 0)
> >>> + continue;
> >>> +
> >>> + enum_list[len].type = i;
> >>> + enum_list[len].name = amdgpu_transfer_function_names[i];
> >>> + len++;
> >>> + }
> >>> +
> >>> + return drm_property_create_enum(dev, DRM_MODE_PROP_ENUM,
> >>> + name, enum_list, len);
> >>> +}
> >>> +
> >>> int
> >>> amdgpu_dm_create_color_properties(struct amdgpu_device *adev)
> >>> {
> >>> @@ -116,11 +157,9 @@ amdgpu_dm_create_color_properties(struct amdgpu_device *adev)
> >>> return -ENOMEM;
> >>> adev->mode_info.plane_degamma_lut_size_property = prop;
> >>>
> >>> - prop = drm_property_create_enum(adev_to_drm(adev),
> >>> - DRM_MODE_PROP_ENUM,
> >>> - "AMD_PLANE_DEGAMMA_TF",
> >>> - amdgpu_transfer_function_enum_list,
> >>> - ARRAY_SIZE(amdgpu_transfer_function_enum_list));
> >>> + prop = amdgpu_create_tf_property(adev_to_drm(adev),
> >>> + "AMD_PLANE_DEGAMMA_TF",
> >>> + amdgpu_eotf);
> >>> if (!prop)
> >>> return -ENOMEM;
> >>> adev->mode_info.plane_degamma_tf_property = prop;
> >>
> >
> >
>