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 20E75EB7EDA for ; Wed, 4 Mar 2026 12:06:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CE4A510E9E6; Wed, 4 Mar 2026 12:06:38 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="key not found in DNS" (0-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="biM+LKOU"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9F4FE10E9E4; Wed, 4 Mar 2026 12:06:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1772625998; x=1804161998; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=ANuuMYO/vF7yQGmzew+xe/nxKl1V6CMtN/3rlr43aRg=; b=biM+LKOUpubSTtakF5JNay6fSpDgMOHHC+j7nre01rHkGZmYGQsdzNo4 uNB9aRETp1jnJmo3P3UjvcGk44MNmGwa4kx0i6t4ThWDXyZMcqynblYcn wYGU4ip1r77upBQoPGEetXAUJHiAfxEVpSKSZsawJqkyGcwLijkRnTUHk qcjI/tnQnjmg5vMLU80NJ0nvdYnKELTGnOBkBQH+fTjPTJUUETmVtiuM2 oCuE4AGCf5E9Z0Ub9xKUkQG0jPMgW5enaIIYZQ6lzDpvdbpH2dz37dP8Q n2HAo7WIId8vOJ3OZ95Yu5QqZ9uK9tSyf5uaEO07IDCDqF93lMRk1b/4w g==; X-CSE-ConnectionGUID: iqyxYYHDQcyA+zIS9iBSxA== X-CSE-MsgGUID: yXgeCXEFTfGujA2muIZb9w== X-IronPort-AV: E=McAfee;i="6800,10657,11718"; a="73810842" X-IronPort-AV: E=Sophos;i="6.21,323,1763452800"; d="scan'208";a="73810842" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2026 04:06:37 -0800 X-CSE-ConnectionGUID: PX7mwvG8Q1mblD52yjdrjA== X-CSE-MsgGUID: iRMkUhxzT3G5QMtFDoJyLQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,323,1763452800"; d="scan'208";a="215698669" Received: from krybak-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.246.84]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2026 04:06:34 -0800 From: Jani Nikula To: "Kandpal, Suraj" , "intel-xe@lists.freedesktop.org" , "intel-gfx@lists.freedesktop.org" Cc: "Murthy, Arun R" Subject: RE: [PATCH v3 1/8] drm/i915/backlight: Use default/max brightness for VESA AUX backlight init 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: <20260224034526.2730130-1-suraj.kandpal@intel.com> <20260224034526.2730130-2-suraj.kandpal@intel.com> <1a76dfe14cbc90b4aaec6f0e54b4e8df9f480efa@intel.com> <9f9be7c4361428b7ccb77dcc04f93b0eda024c8b@intel.com> <676746dc5a9fe839e3ed071dee1c8e89174ce0ea@intel.com> Date: Wed, 04 Mar 2026 14:06:30 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Wed, 04 Mar 2026, "Kandpal, Suraj" wrote: > I did some more digging and for aux_set enabled we really do not need to do get_backlight > And read register again that is filled in probe state and fills up the current_level variable that can be use. > Check drm_edp_backlight_probe_state. > I also found this little comment there > > /* > * If we're not in DPCD control mode yet, the programmed brightness value is meaningless and > * the driver should assume max brightness > */ > return bl->max; > > So this was a policy that was decided during VESA AUX Backlight implementation time. Also that Mode will not be DPCD > Initially and will change later during backlight enable so we get to assume max brightness . That should be okay to do with > Luminance_set case too then. The comment says, if the panel is not in DPCD control mode, the value in DPCD is meaningless. Ditto, if the panel is not in luminance control mode (or whatever the specific name for it is), the luminance value in DPCD is meaningless. However, if the panel is in DPCD control mode but not in luminance control mode, we should be able to read the non-luminance DPCD brightness value and use that. BR, Jani. -- Jani Nikula, Intel