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 95FE2CAC5A7 for ; Wed, 24 Sep 2025 08:34:24 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 06FE810E6AE; Wed, 24 Sep 2025 08:34:24 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="fb/g2IJC"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.17]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6FFBF10E6AE for ; Wed, 24 Sep 2025 08:34:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1758702864; x=1790238864; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=H/J3Sv3iiXuj3P31t7mpXbBohYfIH1zPDDkOjptk2zQ=; b=fb/g2IJCqTyZuIjo3dg7rqh3WMw3v7KwYuGFAIkxRkM3fdFw2u2zsIxj nQn86/U3Ynfa5BSjOMi2YPm26RExukq56SQm0D+oD67Zh0id01FCBmEHb ePU4V2Bo1nMY6Sx96mvUg7Gs+DpSNl8hu3LErSeciB7aJXenwGyIJbQJt uqJncKyUoFeVwOTyi0arqEjaAF8sZfr+sJKdyHxZUbbY9rnSoK5/OCgHV S8/e7xpmI9s468hw6RckEsMc0Nj9DDYw2GW3RuQT1t4WS2pxj5UVIKizP pywa5huRa+aVlsOosiQd2rI7mphYMkY3GsgyXjnf3/YNbX9q5azGZfqQG g==; X-CSE-ConnectionGUID: jHFOTaSuQpKAi9XWJc9tGw== X-CSE-MsgGUID: OEobXa/vRZ2K11i59B4E6w== X-IronPort-AV: E=McAfee;i="6800,10657,11531"; a="60935500" X-IronPort-AV: E=Sophos;i="6.17,312,1747724400"; d="scan'208";a="60935500" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2025 01:34:24 -0700 X-CSE-ConnectionGUID: BaHi5FufToC2SZVGM/42uw== X-CSE-MsgGUID: 2Wf7SeNtRq2iZ2H901awEA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,290,1751266800"; d="scan'208";a="182149956" Received: from rvuia-mobl.ger.corp.intel.com (HELO localhost) ([10.245.245.144]) by orviesa005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2025 01:34:20 -0700 Date: Wed, 24 Sep 2025 11:34:16 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Derek Foreman Cc: Michel =?iso-8859-1?Q?D=E4nzer?= , Chuanyu Tseng , harry.wentland@amd.com, Mario.Limonciello@amd.com, xaver.hugl@gmail.com, victoria@system76.com, seanpaul@google.com, Sunpeng.Li@amd.com, dri-devel@lists.freedesktop.org Subject: Re: [RFC PATCH] drm/uapi: Indroduce a VRR Range Control Interface Message-ID: References: <20250912073305.209777-1-Chuanyu.Tseng@amd.com> <010201993e2cb26f-089ce007-9e30-4b79-b487-c16c360309fd-000000@eu-west-1.amazonses.com> <010201994e05ce63-85ad5afd-fc09-48fc-bd6e-f3716c8ba09f-000000@eu-west-1.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <010201994e05ce63-85ad5afd-fc09-48fc-bd6e-f3716c8ba09f-000000@eu-west-1.amazonses.com> X-Patchwork-Hint: comment Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo 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" On Mon, Sep 15, 2025 at 03:37:07PM +0000, Derek Foreman wrote: > On 9/15/25 5:01 AM, Michel Dänzer wrote: > > On 12.09.25 15:45, Derek Foreman wrote: > >> On 9/12/25 2:33 AM, Chuanyu Tseng wrote: > >>> Introduce a DRM interface for DRM clients to further restrict the > >>> VRR Range within the panel supported VRR range on a per-commit > >>> basis. > >>> > >>> The goal is to give DRM client the ability to do frame-doubling/ > >>> ramping themselves, or to set lower static refresh rates for power > >>> savings. > >> I'm interested in limiting the range of VRR to enable HDMI's QMS/CinemaVRR features - ie: switching to a fixed rate for media playback without incurring screen blackouts/resyncs/"bonks" during the switch. > >> > >> I could see using an interface such as this to do the frame rate limiting, by setting the lower and upper bounds both to a media file's framerate. However for that use case it's not precise enough, as video may have a rate like 23.9760239... FPS. > >> > >> Would it be better to expose the limits as a numerator/denominator pair so a rate can be something like 24000/1001fps? > > I was thinking the properties could allow directly specifying the minimum and maximum number of total scanlines per refresh cycle, based on the assumption the driver needs to program something along those lines. > > Surprisingly, this would also not be precise enough for exact media > playback, as the exact intended framerate might not result in an integer > number of scan lines. When that happens a QMS/CinemaVRR capable HDMI > source is expected to periodically post a frame with a single extra scan > line to minimize the error. Intel VRR hardware has a "CMRR" feature where it can automagically tweak the vtotal between frames to maintain a non integer average. As for knobs to limit the min/max refresh rates, technically you wouldn't need the max knob because that is ultimately defined by the vtotal of the supplied timings. But I guess if you have a knob to limit the min then a max knob might be convenient as well. -- Ville Syrjälä Intel