From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D4AF2354AF2 for ; Tue, 27 Jan 2026 14:57:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769525854; cv=none; b=GK2JgHCdMqsH7EJDOsHEpXP6VcxnFRXPrBRQcV/WSGLQ9kMAkzZdVnPal4uoMZqxOQDm1EUPhKquNBQz4dMBCv4POvfX6+Q0SemIZqtsuaJRo450043VjFMBdwd/xHvpowGleUBw89t/vlDBwpiQW5Y4ky0VYLwqQnqwmlLECD4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769525854; c=relaxed/simple; bh=GF3hAJ+nQjE0sguR8uHzep8IWqz/2IX5fpA+BkSPp4w=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=QSup2hKlqStGT7UHlfeoC4VaX7ilGcdTVhN6dFjA0zMkSrVCnBn4dTxgAu5XwDb37TEi+3elQgfWzKDYiW7iot/tiJSbpOnjIWm3npM2R3Uthc82uy+ggTrcYsTsEfJ/AI5M8XN81UyewOJFqbGbjiQzuboV4DBLGkiMfyTWpTo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=j1ArsMBJ; arc=none smtp.client-ip=198.175.65.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="j1ArsMBJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1769525853; x=1801061853; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=GF3hAJ+nQjE0sguR8uHzep8IWqz/2IX5fpA+BkSPp4w=; b=j1ArsMBJTGScU8+yEClg/DTFW5jHjo/Gs2sOO7SWDQCQXTqcQb/FmcuE 4BtPygO/k5Dz6p1l4KYZg1Mh2g1vMau13t3Hb4ZZt/6r3lsVThALJhnSW jq1WoivChW710AnBokqBGEM0aiws2Jfe8vivIK7BeM9PdlTy6QmTM/nUH h9lbbEPCUB9/cI7Rz8ie3s8tzwcNsWXH27YTCYRFAMogG0mEamAs2RrVs M9GFy1Yr14YcuHSPO5RCI01/ceW//+BG3GKsp+vXfupXgezMMOIcyQOPq 5vha4zUPCeYeMf0UpMAFtCuoYV3nznxfE5N5JN7wx+dHMRDHWx6EoLSCg Q==; X-CSE-ConnectionGUID: 7tpKNaHNTiaFEzbs9l0TyA== X-CSE-MsgGUID: WujS3JMcRN6VqC1cZYmTCA== X-IronPort-AV: E=McAfee;i="6800,10657,11684"; a="70763155" X-IronPort-AV: E=Sophos;i="6.21,257,1763452800"; d="scan'208";a="70763155" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by orvoesa110.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2026 06:57:32 -0800 X-CSE-ConnectionGUID: CWJZdYcwSGiBiYbsJazt4w== X-CSE-MsgGUID: WHorqjZERjayIlJYB6grxw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,257,1763452800"; d="scan'208";a="208242096" Received: from mjarzebo-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.246.148]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2026 06:57:28 -0800 From: Jani Nikula To: Atharva Tiwari Cc: airlied@gmail.com, atharvatiwarilinuxdev@gmail.com, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, joonas.lahtinen@linux.intel.com, linux-kernel@vger.kernel.org, rodrigo.vivi@intel.com, simona@ffwll.ch, tursulin@ursulin.net, ville.syrjala@linux.intel.com Subject: Re: [PATCH 2/2] drm/i915/display: Disable display for iMac's In-Reply-To: <20260126204915.1324-1-atharvatiwarilinuxdev@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland References: <20260126204915.1324-1-atharvatiwarilinuxdev@gmail.com> Date: Tue, 27 Jan 2026 16:57:25 +0200 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, 26 Jan 2026, Atharva Tiwari wrote: >> Rendering and display are quite separate in the hardware and in the >> driver. Perhaps you do not mean "rendering" here? Perhaps it can be used >> for rendering but not display? > > Yeah, it can be used for rendering but not display, sorry for the wording. > >> Okay, so perhaps there's no eDP connected. But what about the other >> connectors on the iGPU? What about everything else in the display >> hardware? > > You cant use the iGPU to drive the display on any hardware (including external displays). > >> If you can figure out that it's specifically link training that fails (a >> dmesg would be useful to show this) there clearly is display hardware, >> right? > > As said the iGPU cant drive the display on all monitors (even on macOS), but still heres the dmesg before this patch: > > [ 5.095489] i915 0000:00:02.0: [drm] Found cometlake (device ID 9bc8) integrated display version 9.00 stepping N/A > [ 5.096061] i915 0000:00:02.0: [drm] VT-d active for gfx access > [ 5.096102] i915 0000:00:02.0: [drm] Using Transparent Hugepages > [ 5.099214] i915 0000:00:02.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff > [ 5.099217] i915 0000:00:02.0: [drm] Failed to find VBIOS tables (VBT) > [ 5.099324] i915 0000:00:02.0: vgaarb: VGA decodes changed: olddecodes=io+mem,decodes=none:owns=io+mem > [ 5.100960] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/kbl_dmc_ver1_04.bin (v1.4) > [ 5.832214] i915 0000:00:02.0: [drm] [ENCODER:105:DDI A/PHY A] failed to retrieve link info, disabling eDP > [ 5.835756] i915 0000:00:02.0: [drm] Registered 3 planes with drm panic > [ 6.428455] i915 0000:00:02.0: [drm] Cannot find any crtc or sizes > [ 6.722404] i915 0000:00:02.0: [drm] Cannot find any crtc or sizes > >> There's at least three levels where this could be handled, depending on >> details: >> >> - Display probe (the patch at hand). Assumes there's no display >> hardware, at all. The driver doesn't touch the hardware, which >> continues to consume power, it's not put in low power states. Not >> optimal if there actually is display hardware. >> >> - Display disable. See intel_display_device_enabled(). The driver takes >> over the hardware, puts it to sleep, but prevents all connectors from >> being connected. At a glance, this seems like the appropriate level. What if you drop patch 2 and supply i915.disable_display=1 module parameter? Or return false from intel_display_device_enabled(). BR, Jani. >> >> - eDP disable. Add a quirk somewhere to enforce eDP is disconnected, but >> other connectors can be used. > > The main reason I sent this patch is that after i915 trys to probe the display, > the dGPU (amdgpu) is no longer able to detect the internal display, > resulting in a black screen. > >> It would be quite useful to indicate the PCI ID of the device in >> question. > > 00:02.0 VGA compatible controller [0300]: Intel Corporation CometLake-S GT2 [UHD Graphics 630] [8086:9bc8] (rev 03) (prog-if 00 [VGA controller]) > Subsystem: Apple Inc. CometLake-S GT2 [UHD Graphics 630] [106b:ffff] -- Jani Nikula, Intel