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Tue, 29 Sep 2026 01:35:06 +0000 Message-ID: <392ba6d1-1ff8-4ba0-8b71-d794336cf4e9@amd.com> Date: Tue, 29 Sep 2026 09:35:01 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND 1/2] drm/amd/display: Use linear backlight curve in power module To: Matthew Schwartz , "Wentland, Harry" , "Li, Sun peng (Leo)" , "Deucher, Alexander" Cc: "Limonciello, Mario" , "amd-gfx@lists.freedesktop.org" , "dri-devel@lists.freedesktop.org" References: <20260916191102.1195881-1-matthew.schwartz@linux.dev> Content-Language: en-US From: Ray Wu In-Reply-To: <20260916191102.1195881-1-matthew.schwartz@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: TYCP286CA0358.JPNP286.PROD.OUTLOOK.COM (2603:1096:405:7c::9) To CHAPR12MB999225.namprd12.prod.outlook.com (2603:10b6:610:2fe::11) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CHAPR12MB999225:EE_|DS7PR12MB5813:EE_ X-MS-Office365-Filtering-Correlation-Id: 8d18537c-df48-4d24-a821-08df1dc9e3f6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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If you still see any other issues, please feel free to send an updated patch. Thanks! On 9/17/2026 3:11 AM, Matthew Schwartz wrote: > amdgpu_dm already applies the ATIF custom brightness curve in > convert_custom_brightness() before handing the level to the power > module. The power module then builds its own percent to PWM LUT from > the same ATIF data in initialize_backlight_caps() and applies the curve > a second time. On the Lenovo Legion Go S this maps the bottom 40% of the > brightness range to under 12% PWM, where the panel no longer visibly > changes. > > Tell the power module to use its linear curve so the PWM is a straight > rescale of the level DM computed, matching the behavior before the power > module took over backlight programming. > > Fixes: 3c108046e1d6 ("drm/amd/display: Add power module on Linux") > Signed-off-by: Matthew Schwartz > --- > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > index ca795cda8084..63acefc0acfb 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > @@ -455,7 +455,7 @@ STATIC_IFN_KUNIT int amdgpu_dm_init_power_module(struct amdgpu_display_manager * > !(amdgpu_dc_feature_mask & DC_DISABLE_FRACTIONAL_PWM_MASK); > init_data[i].use_custom_backlight_caps = false; > init_data[i].custom_backlight_caps_config_no = 0; > - init_data[i].use_linear_backlight_curve = false; > + init_data[i].use_linear_backlight_curve = true; > init_data[i].def_varibright_enable = 0; > init_data[i].varibright_level = 0; > /*