From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 79C99C5AE49 for ; Mon, 10 Aug 2026 14:25:40 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AB2D510E8AD; Mon, 10 Aug 2026 14:25:39 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="C1E8DfzV"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id D3F2510E8AD for ; Mon, 10 Aug 2026 14:25:38 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id C356160254 for ; Mon, 10 Aug 2026 14:25:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPS id 7ADA8C2BCF4 for ; Mon, 10 Aug 2026 14:25:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1786371937; bh=WxabGio6tZH5p3RgYjBVTuwx+db08oGwAzjsFjD/wnk=; h=From:To:Subject:Date:From; b=C1E8DfzVw/Bd/fQPb5OmVOlgb73dRqul2rW0Fl5jndmt9vZ6DUSpK/vdnHMUamokZ IuVx33ISb2gyG+gNxA9259exgJcER8nb+JANXHBIBIw5czKCGQaXJGEcbpsomSYgyk K8d1cbm8KeTM/v9ffRQd/OyFe6xLK1CToY4Pu6NsctlqvbmlgV8IngfTCAnRdMDAEI zTeZ5ObeTjNka6tOzpnNcgkaIlruUkXB4KVJsK/xpQwTA8QoZqxYv/QokLNSFWQwPH j0sy2q+AjtcYH66YWZmcT3AycFYBxxzQBTmkM+cJ6AEgwdZ0GqUDseBp6NKeAzG4rG L0V2MzhwowQPQ== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id 58E54C53BC5; Mon, 10 Aug 2026 14:25:37 +0000 (UTC) From: bugzilla-daemon@kernel.org To: dri-devel@lists.freedesktop.org Subject: [Bug 221865] New: amdgpu: brightness 100% blacks out screen Date: Mon, 10 Aug 2026 14:25:37 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: AssignedTo drivers_video-dri@kernel-bugs.osdl.org X-Bugzilla-Product: Drivers X-Bugzilla-Component: Video(DRI - non Intel) X-Bugzilla-Version: 2.5 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: me@metantesan.com X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: drivers_video-dri@kernel-bugs.osdl.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter cf_regression Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" https://bugzilla.kernel.org/show_bug.cgi?id=3D221865 Bug ID: 221865 Summary: amdgpu: brightness 100% blacks out screen Product: Drivers Version: 2.5 Hardware: AMD OS: Linux Status: NEW Severity: normal Priority: P3 Component: Video(DRI - non Intel) Assignee: drivers_video-dri@kernel-bugs.osdl.org Reporter: me@metantesan.com Regression: No Hardware: - ASUS ROG laptop, AMD Phoenix1 APU (DCN 3.1.4), eDP panel BOE NE134WUM-N82 (EISA BOE0B4A) - Kernel 7.1.6 (regression: 7.1.5 works fine) Symptom: Setting backlight above ~98.4% makes the internal display go black. Setting it back down recovers instantly. Diagnosis via amdgpu_dm_brightness tracepoint (/sys/kernel/tracing): requested=3D64200 converted=3D65302 (works) requested=3D64300 converted=3D65535 (true max, works) requested=3D64500 converted=3D65535 (true max, works) requested=3D64540 converted=3D65768 (> 65535, BLACK) requested=3D65535 converted=3D66702 (> 65535, BLACK) Root cause: convert_custom_brightness() in drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c: *user_brightness =3D scale_fw_to_input(min, max, DIV_ROUND_CLOSEST(lum * brightness, 101)); The panel's ATIF QUERY_BRIGHTNESS_TRANSFER_CHARACTERISTICS (from ASUS BIOS) returns luminance data points >100 (~103). So lum * brightness / 101 exceeds 65535, and the result is passed as backlight_pwm_u16_16 (u16) to dc_link_set_backlight_level(), truncating to ~232 =E2=86=92 black screen. Regression: 7.1.6 changed amdgpu_dm_register_backlight_device() from props.max_brightness =3D max - min / (max-min)*level/100 to max / max*level= /100, exposing the overflow zone to userspace. 7.1.5's 100% mapped below the over= flow threshold. Suggested fix: clamp the converted level to max (this is what the hardware accepts =E2=80=94 65535 is valid full brightness, the plateau at requested = 64300=E2=80=9364500 proves it): static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_ca= ps *caps, uint32_t brightness) { unsigned int min, max; if (!get_brightness_range(caps, &min, &max)) return brightness; convert_custom_brightness(caps, min, max, &brightness); return min_t(u32, min + DIV_ROUND_CLOSEST_ULL((u64)(max - min) * brightness, max), max); } --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=