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 2E96AC5DF66 for ; Mon, 17 Aug 2026 12:09:01 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9123610E783; Mon, 17 Aug 2026 12:09:00 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="Dgwi863J"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.17]) by gabe.freedesktop.org (Postfix) with ESMTPS id 640C610E783 for ; Mon, 17 Aug 2026 12:08:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1786968539; x=1818504539; h=from:to:subject:in-reply-to:references:date:message-id: mime-version:content-transfer-encoding; bh=C5/1ARkhSi9RNOuaAXeKaoHPgUlvX8P0PZmlqEQN5Fg=; b=Dgwi863JYlIQoTQsXIlxZOBKbZyewT/LvgWQIsOZ52A2xmVa1aWsWMPU kzOknTiALr4RHMPUNSXKaZr+ZTV5kwYLeRCqd917dWS7vao/ZnF92kFsm l/8QIVNYN1ARtpQsXA7xPDwNuL7xT6MNkjmQrOHEV5NQWRX9YdZTdErOD kIqwXA1Qjt/33s6Fk7LqiJUcVb95Q8cD+fuHnLRlhCN+KirVKQBR69o3j m8gIFha6rJ4nZYhzc65mo7Ko5gxL2tMbI23m5VBCK/1/WzC6po3gVRnzp sCqhaOsFpQuwsw2nBMkswRjzv0lbJw36s1tm8AOl9sI+WE21QG1D61ebe w==; X-CSE-ConnectionGUID: jClE+4fwRli45LL4CBgPKg== X-CSE-MsgGUID: +t/syXzqQg+Uv9EyiXvgog== X-IronPort-AV: E=McAfee;i="6800,10657,11877"; a="87462636" X-IronPort-AV: E=Sophos;i="6.25,228,1779174000"; d="scan'208";a="87462636" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2026 05:08:58 -0700 X-CSE-ConnectionGUID: hoLGTOibTfqBA2QtdGa8Hg== X-CSE-MsgGUID: 0+BUc1efSaSyrZYMX4HQRA== X-ExtLoop1: 1 Received: from abityuts-desk1.ger.corp.intel.com (HELO localhost) ([10.245.245.110]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2026 05:08:56 -0700 From: Jani Nikula To: Novej Panjawani , intel-gfx@lists.freedesktop.org Subject: Re: [BUG] i915/ADL-P eDP: link training exits with adj_req=0x11 unresolved, causing modeset loop on CMN14E7 (Dell Latitude 5430) In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland References: Date: Mon, 17 Aug 2026 15:08:54 +0300 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Sun, 16 Aug 2026, Novej Panjawani wrote: > ## Summary > > After boot and after any display mode change (HDMI connect/disconnect),=20 > the internal eDP display on this Dell Latitude 5430 (ADL-P, Intel Iris=20 > Xe 46A8) enters an **infinite modeset loop** that repeats every ~2=20 > seconds: backlight off =E2=86=92 pipe disabled =E2=86=92 link retrain =E2= =86=92 pipe enabled =E2=86=92=20 > backlight on =E2=86=92 repeat. This produces continuous visible black-scr= een=20 > flashing. The loop self-resolves after ~5=E2=80=9315 minutes (thermal=20 > stabilization of the eDP connection), and is immediately re-triggered by= =20 > any subsequent mode change. Please file a bug as described at [1]. BR, Jani. [1] https://drm.pages.freedesktop.org/intel-docs/how-to-file-i915-bugs.html > > External HDMI display is not affected. > > ## Hardware / Environment > > | | | > |---|---| > | **System** | Dell Latitude 5430 | > | **GPU** | Intel Alder Lake-P, Iris Xe Graphics =E2=80=94 PCI `0000:00:0= 2.0`,=20 > Device ID `0x46A8` | > | **Panel** | Chimei Innolux CMN14E7 =E2=80=94 14" 1920=C3=971080, eDP 1.= 4, EDID 1.4 | > | **Kernel** | `6.18.40-1-cachyos-lts` (clang 22.1.8, LLD 22.1.8) | > | **i915** | 1.6.0 =E2=80=94 GuC 70.49.4, DMC adlp_dmc.bin v2.20, HuC 7.9= .3 | > | **BIOS** | Dell 1.36.0 (2025-12-23) =E2=80=94 latest per fwupd | > > ## Root Cause > > With `drm.debug=3D0x04`, the following loop is captured every ~2 seconds: > > 1. `intel_dp_start_link_train` uses **vswing 0/0/0/0, pre-emph 0/0/0/0**= =20 > at `LINK_BW_SET=3D0x0a` (HBR / 2.7 Gbps), 2 lanes > 2. TPS1 and TPS2 complete =E2=80=94 `"Channel EQ done. DP Training succes= sful"` > 3. Pipe A and backlight are enabled (PWM =3D 23718) > 4. ~2 seconds later, link status check: > =C2=A0 =C2=A0- Read 1: `align:0x80 sink:0x3 adj_req0_1:0x11` =E2=80=94 a= ligned, but panel=20 > requesting vswing level 1 > =C2=A0 =C2=A0- Read 2: `align:0x0 sink:0x1 adj_req0_1:0x11` =E2=80=94 **= alignment lost,=20 > symbol lock lost** > 5. Driver detects link loss =E2=86=92 full modeset (backlight off, pipe d= isabled) > 6. Repeat from step 1 > > **`adj_req0_1=3D0x11` (vswing level 1 requested for lanes 0/1) appears in= =20 > every DPCD read throughout the flicker window.** The driver exits=20 > training while adj_req is non-zero and does not apply the requested=20 > levels to the operational link. The panel cannot sustain HBR at level 0,= =20 > degrades within ~2 seconds, fires IRQ_HPD, the driver responds with a=20 > full modeset, and the cycle repeats. > > ## Debug Log (one complete cycle) > > Captured with `drm.debug=3D0x04`: > > ``` > i915: [drm:intel_dp_start_link_train] Using LINK_BW_SET value 0a > i915: [drm:intel_dp_set_signal_levels] 8b/10b, lanes: 2, vswing levels:=20 > 0/0/0/0, pre-emphasis levels: 0/0/0/0 > i915: [drm:intel_dp_link_train_phy] Clock recovery OK > i915: [drm:intel_dp_link_train_phy] Channel EQ done. DP Training successf= ul > i915: [drm:intel_dp_link_train_phy] Link Training passed at link rate =3D= =20 > 270000, lane count =3D 2 > i915: enabling pipe A > i915: [drm:cnp_enable_backlight] set backlight PWM =3D 23718 > > -- ~2 seconds -- > > i915: [drm:intel_dp_dump_link_status] ln0_1:0x73 align:0x80 sink:0x3=20 > adj_req0_1:0x11=C2=A0 =C2=A0<-- link ok, but adj_req non-zero > i915: [drm:intel_dp_dump_link_status] ln0_1:0x73 align:0x0 sink:0x1=20 > adj_req0_1:0x11=C2=A0 =C2=A0<-- link lost > > i915: [drm:cnp_disable_backlight] set backlight PWM =3D 0 > i915: [drm:intel_disable_transcoder] disabling pipe A > i915: [drm:intel_hpd_irq_handler] Received HPD interrupt on PIN 4 - cnt: = 10 > i915: [drm:intel_dp_hpd_pulse] ignoring long hpd on eDP [ENCODER:262:DDI= =20 > A/PHY A] > > -- repeat every ~2 seconds -- > ``` > > ## Reproduction > > 1. Append `drm.debug=3D0x04` to kernel cmdline, reboot > 2. `journalctl -k -f | grep -E=20 > "link_train|dump_link|hpd|backlight|transcoder"` > 3. Cycle appears within seconds of display init, repeats every ~2 seconds > 4. After 5=E2=80=9315 min, cycle stops (thermal stabilization) > 5. Retrigger: unplug external display =E2=86=92 cycle immediately resumes > > ## Expected Behaviour > > Either: > - **(a)** The TPS2 loop should continue iterating and updating=20 > vswing/pre-emph until `adj_req` is zero before declaring training=20 > successful; or > - **(b)** After training exits, the driver should apply the final=20 > `adj_req` vswing values to the DDI buffer translation used for normal=20 > operation > > ## Attempted Workarounds (all ineffective) > > None of the following affect link training vswing behavior: > - `i915.enable_psr=3D0`, `i915.enable_panel_replay=3D0` > - `i915.enable_dc=3D0`, `i915.enable_sagv=3D0`, `i915.enable_fbc=3D0`,=20 > `i915.enable_dsb=3D0` > - `i915.edp_vswing=3D2` =E2=80=94 selects 400 mV DDI translation table bu= t does=20 > not force vswing level 1 in the training loop > - `i915.enable_rc6=3D0` =E2=80=94 silently ignored ("unknown parameter");= GuC RC=20 > remains active > - `xe.force_probe=3D46a8` =E2=80=94 xe exhibits a separate fatal bug: con= tinuous=20 > GTT plane faults in stolen framebuffer memory (~300K=E2=80=93600K suppres= sed=20 > callbacks per 5 seconds) > > ## Notes > > - Issue self-resolves after thermal warmup, strongly suggesting the=20 > physical link is borderline at HBR/level-0 =E2=80=94 applying level 1 sho= uld=20 > resolve it permanently > - BIOS 1.36.0 is the latest (confirmed via fwupd) > - External HDMI (pipe B) is unaffected throughout > --=20 Jani Nikula, Intel