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 DE1E4C433F5 for ; Wed, 27 Apr 2022 15:02:24 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 402B110EEB8; Wed, 27 Apr 2022 15:02:24 +0000 (UTC) Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [IPv6:2001:67c:2050:0:465::101]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7EFDC10F4E7 for ; Wed, 27 Apr 2022 15:02:22 +0000 (UTC) Received: from smtp102.mailbox.org (smtp102.mailbox.org [80.241.60.233]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-101.mailbox.org (Postfix) with ESMTPS id 4KpMRc2wt0z9sWx; Wed, 27 Apr 2022 17:02:20 +0200 (CEST) Message-ID: <8ced7101-34b3-24d3-ed78-0951abce0573@mailbox.org> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1651071738; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sWh5ihS06LiSpcSmL+YdrqQ7AY3GBdO1PruiyfJmaP0=; b=vRBY5FOZuWqrgUzYGNA6UaC7hvkRIP9CniuQ0c1lOdxr9HMy+mZiyQWy00xsxQj7nvo/f2 yUwwpgXFl49YTyfAr/PYyln3MHXbR//j/429HirEfq4i8al9uGsnP/zooWonlsLbMcUppa wxDcfNSGlgbHJgPGiJMhsl0LYPwoRk69KXHv6WfIdlRoQYsiE9NnLePO2Mlz5SqHpVO5a3 MgYwUqx77NaG1Vyc6p0BwV4SBfnlin+Fefsa5sPJuuz6iRwXUnI5Zgtdf8ZfulUZ6GoJmS bdpyOGT+TnHXCxbEQRsazjcZWFjOqCAsgPEckDItwALjRq6mH9uoShAL3P98nA== Date: Wed, 27 Apr 2022 17:02:14 +0200 MIME-Version: 1.0 Subject: Re: How should "max bpc" KMS property work? Content-Language: en-CA To: Pekka Paalanen , =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= References: <20220426113502.224d0a90@eldfell> <20220427135259.5e615945@eldfell> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= In-Reply-To: <20220427135259.5e615945@eldfell> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-MBO-RS-META: ybuqs7oq77wudqf9b6c4ro7qycarfows X-MBO-RS-ID: 679f264f75adc1f9408 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: , Cc: Sebastian Wick , =?UTF-8?Q?Jonas_=c3=85dahl?= , dri-devel , Vitaly Prosyak Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 2022-04-27 12:52, Pekka Paalanen wrote: > On Tue, 26 Apr 2022 20:55:14 +0300 > Ville Syrjälä wrote: >> On Tue, Apr 26, 2022 at 11:35:02AM +0300, Pekka Paalanen wrote: >>> >>> Do I lose the ability to set video modes that take too much bandwidth >>> at uncapped driver-selected bpc while capping the bpc lower would allow >>> me to use those video modes? >>> >>> Or, are drivers required to choose a lower-than-usual but highest >>> usable bpc to make the requested video mode squeeze through the >>> connector and link? >> >> IMO drivers should implement the "reduce bpc until it fits" >> fallback. We have that in i915, except for MST where we'd need >> to potentially involve multiple streams in the fallback. That >> is something we intend to remedy eventually but it's not an >> entirely trivial thing to implement so will take some actual >> work. ATM we just cap MST to <=8bpc to avoid users getting into >> this situation so often. > > Excellent, but judging from what Alex said, this is also not what > amdgpu does. We have two drivers doing different things then? > > So with Weston I probably have to document, that if you can't get the > video mode you want working, try turning the 'max bpc' knob down and > try again. > > Or, I could cap 'max bpc' based on my framebuffer depth. If I have an > electrical 8 bit FB (default in Weston), then there is not much use for > having 'max bpc' > 8. This ignores the KMS color pipeline a bit. Does > that make sense? I don't think so. The output of LUTs in current HW has at least 10 bpc, regardless of the FB format. -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and Xwayland developer