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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 24D83CD5BB1 for ; Mon, 25 May 2026 12:10:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cY3kcG400HFwYsUxYZRg6ciJDEvU+8cftVFMVGBbPaY=; b=lLR3ygayeBFCuhHk61DzE2SjJL sLo1Vne4NvPJrZ09MdMudyQykpComq/3K+DB9gfqhY0GQ3zAFrl02N1GU14gAgWNpaF4KWKZxp88k sm76XF7tX6PstPwe0qmM8AwKr9EljAqqt8Ui5s3XPHo3cF8kDs2owMHfmLcbYlSjn5iG6/KI1iV2s ukT65oF3AH6J2J2dcfX/ScMiH+96YNCHV468sZqFqY24sWv5WfVjgbsZpBPUPIDvi1a+uJuWjhyCv OPGec+XczXLoZ5c6e2rU8Kem1MiGTlgQTHurRGpmk7MZfFO1Sqd54HNfYuVa3iAqctaoJL96dmiFz ejY7bwCA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRU8t-0000000HA1n-40bx; Mon, 25 May 2026 12:10:47 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRU8r-0000000HA1D-3KE6 for linux-arm-kernel@lists.infradead.org; Mon, 25 May 2026 12:10:46 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 8C523405C1; Mon, 25 May 2026 12:10:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A5F01F000E9; Mon, 25 May 2026 12:10:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779711044; bh=cY3kcG400HFwYsUxYZRg6ciJDEvU+8cftVFMVGBbPaY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=e0vfZklMVREIcM48htGLKBOoKgczK+3z159ZNICbWDo5cIBwe8Y1T3i34odJaqUQ2 Vld1PyeCsRJZe7OpBupoSgSawZaKa0GVVGj43du8T0L77MVrAk7j96PmyYIpo4Xg/7 XK61MwNjMJZTU30cuggpqK+i0sis5A8GNivm1LrbtFvBuYhzR2B/R0HUdqmU6xlKUq e7MCvKSDwh1X+csDniDFg40DRIsufkKdV2cJR0m3vM7Fkvzrr3TK8PrMMo+gA+B69F 4UScN3rtheKMHVDbCCOqxJ5h/doX9qgRH1dalJxGOj6tNVZqW4DfvNSX42NnaSwFMd 1WpRMRpVdM5cA== Message-ID: <032c1099-40ab-470e-8cc3-af6d3cad22d4@kernel.org> Date: Mon, 25 May 2026 14:10:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 7/8] dt-bindings: display: allwinner: Split H616 DE33 layer reg space To: wens@kernel.org Cc: Jernej Skrabec , samuel@sholland.org, mripard@kernel.org, maarten.lankhorst@linux.intel.com, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, mturquette@baylibre.com, sboyd@kernel.org, dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org References: <20260509190015.79086-1-jernej.skrabec@siol.net> <20260509190015.79086-8-jernej.skrabec@siol.net> <20260514-valiant-ape-of-discourse-a4f5a9@quoll> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260525_051045_875828_95EA7F36 X-CRM114-Status: GOOD ( 19.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 24/05/2026 23:33, Chen-Yu Tsai wrote: > Hi, > > (resent from new email) > > On Thu, May 14, 2026 at 2:04 PM Krzysztof Kozlowski wrote: >> >> On Sat, May 09, 2026 at 09:00:14PM +0200, Jernej Skrabec wrote: >>> From: Jernej Skrabec >>> >>> As it turns out, current H616 DE33 binding was written based on >>> incomplete understanding of DE33 design. Namely, planes are shared >>> resource and not tied to specific mixer, which was the case for previous >>> generations of Display Engine (DE3 and earlier). >>> >>> This means that current DE33 binding doesn't properly reflect HW and >>> using it would mean that second mixer (used for second display output) >>> can't be supported. >>> >>> Remove layer register space, which will be represented with additional >>> node, and replace it with phandle, which will point to that new, shared >>> node. That way, all mixers can share same layers. >>> >>> There is no user of this binding yet, so changes can be made safely, >>> without breaking any backward compatibility. >> >> There is user. git grep gives me: >> drivers/gpu/drm/sun4i/sun8i_mixer.c >> >> which means this is a released ABI. As I understood, the old code was > > We held off on merging the DT changes so that we could rework this. > I can't find the actual request though. It was probably over IRC. > >> working fine but just did not support all use cases. Why this cannot be >> kept backwards compatible? > > AFAIK the "planes" block is shared between two display mixers. As the > commit message explains, this prevents using the second mixer, since > only one of them can claim and map the register space. And on the H700 > (which is the same die as the H616 discussed here but with more exposed > interfaces), there could actually be a use case for the second mixer. It explains why you want to make the changes but not why you cannot keep it backwards compatible. Best regards, Krzysztof