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David Alan Gilbert'" , Bhawanpreet Lakha , Aurabindo Pillai , Matthew Schwartz , pekka.paalanen@collabora.com, robert.mader@posteo.de, amd-gfx@lists.freedesktop.org, kernel-dev@igalia.com, linux-kernel@vger.kernel.org References: <20260819161106.27702-1-mwen@igalia.com> <20260819161106.27702-2-mwen@igalia.com> Content-Language: en-US From: Alex Hung In-Reply-To: <20260819161106.27702-2-mwen@igalia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4PR04CA0279.namprd04.prod.outlook.com (2603:10b6:303:89::14) To DM4PR12MB8476.namprd12.prod.outlook.com (2603:10b6:8:17e::15) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR12MB8476:EE_|DS7PR12MB8417:EE_ X-MS-Office365-Filtering-Correlation-Id: 92019010-ac95-4125-13a9-08defe24810c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|366016|23010399003|1800799024|376014|10067099003|11063799006|4143699003|56012099006|22082099003|18002099003|3023799007; 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Are they intentional? ERROR: Please use git commit description style 'commit <12+ chars of sha1> ("")' - ie: 'commit de17c6bb7072 ("drm/amd/display: use halving distribution for PQ/sRGB linearizing LUT")' #13: any encoded input, so remove the PQ/sRGB condition from de17c6bb7072 and WARNING: Possible repeated word: 'segments' #67: FILE: drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c:349: + /* 9 segments + * segments are from 2^-9 to 2^0 total: 1 errors, 1 warnings, 47 lines checked On 8/19/26 10:00, Melissa Wen wrote: > In encode-to-linear conversions, LUT entries should be uniformly > distributed across the input range: non-linear encodings are already > approximately perceptually uniform, so every input code carries the same > weight. A fixed count per region does the opposite, concentrating > entries on the darker values and leaving few for the bright end, whereas > halving distribution spaces all 256 entries uniformly. This holds for > any encoded input, so remove the PQ/sRGB condition from de17c6bb7072 and> apply halving to all encode-to-linear operations (pre-defined TF or user > LUTs). > > It fixes the following IGT kms_colorop subtests: > - plane-XR30-XR30-srgb_inv_eotf_lut-srgb_eotf_lut > - plane-XR30-XR30-gamma_2_2-gamma_2_2_inv-gamma_2_2 > > Fixes: de17c6bb7072 ("drm/amd/display: use halving distribution for PQ/sRGB linearizing LUT") > Reviewed-by: Harry Wentland <harry.wentland@amd.com> > Signed-off-by: Melissa Wen <mwen@igalia.com> > --- > .../amd/display/dc/dcn30/dcn30_cm_common.c | 34 ++++++------------- > 1 file changed, 10 insertions(+), 24 deletions(-) > > diff --git a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c > index 66fe7f313ea3..62ca235cd649 100644 > --- a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c > +++ b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c > @@ -320,6 +320,8 @@ static struct fixed31_32 interp_tf_pts(const struct fixed31_32 *output_tf_channe > return value; > } > > +#define NUM_DEGAMMA_REGIONS 9 > + > bool cm3_helper_translate_curve_to_degamma_hw_format( > const struct dc_transfer_func *output_tf, > struct pwl_params *lut_params) > @@ -343,31 +345,15 @@ bool cm3_helper_translate_curve_to_degamma_hw_format( > memset(lut_params, 0, sizeof(struct pwl_params)); > memset(seg_distr, 0, sizeof(seg_distr)); > > - if (output_tf->tf == TRANSFER_FUNCTION_PQ || > - output_tf->tf == TRANSFER_FUNCTION_SRGB) { > - /* 9 segments > - * segments are from 2^-9 to 0 > - */ > - const uint8_t SEG_COUNT = 9; > - seg_distr[0] = 0; // Since we only have one point in darkest region > - for (k = 1; k < SEG_COUNT; k++) > - seg_distr[k] = k - 1; // 2^(k-1) points per region; halves as k decreases > + /* 9 segments > + * segments are from 2^-9 to 2^0 > + */ > + seg_distr[0] = 0; // Since we only have one point in darkest region > + for (k = 1; k < NUM_DEGAMMA_REGIONS; k++) > + seg_distr[k] = k - 1; // 2^(k-1) points per region; halves as k decreases > > - region_start = -SEG_COUNT; > - region_end = 0; > - } else { > - /* 12 segments > - * segments are from 2^-12 to 2^0 > - * There are less than 256 points, for optimization > - */ > - const uint8_t SEG_COUNT = 12; > - > - for (i = 0; i < SEG_COUNT; i++) > - seg_distr[i] = 4; > - > - region_start = -SEG_COUNT; > - region_end = 0; > - } > + region_start = -NUM_DEGAMMA_REGIONS; > + region_end = 0; > > for (i = region_end - region_start; i < MAX_REGIONS_NUMBER ; i++) > seg_distr[i] = -1;