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 D07A1C83030 for ; Mon, 30 Jun 2025 11:54:06 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=3y+b2j8+A8W8uv2oLAi6010Yh9nmeGSj5kggJO53OS8=; b=FhD0PTDpJuZtaqw+e9LY23Q9Ch S5SOvxw3mDFpuLg0iFKINmfM8s4gaRmHh/D4RNIxpI54Xi++7ZQmklf8hcvliYxAnbf9KxWS5HW7v ebmiBHt1JiwyM/oXlfbEpC0UXPrYFVJXLiy3GKULSrAbm/ePtCbqMzOsgHogXW6e0h8Jhpw3mZXje h3FqBXD/8r58kgFHiktxc92/7PZ7Me0J6pIUwVrPb5gLZbyLOL/tKAV5Sz7fbCgZwrff61EgJmNoz XZfm8iRv4Kefjk3A/mbY4UBSI9ZvzqA4V9ycOmjbBTB2/i8mMjpRx4rhb7PB/vp0HeL6TEFrgZkjb cXwOLSgw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uWD5F-000000026mW-06XD; Mon, 30 Jun 2025 11:54:01 +0000 Received: from perceval.ideasonboard.com ([213.167.242.64]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uWCia-000000022DC-17Li for linux-arm-kernel@lists.infradead.org; Mon, 30 Jun 2025 11:30:37 +0000 Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 55B53928; Mon, 30 Jun 2025 13:30:12 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1751283012; bh=f8UGTCDHYUrbrwvxFMRydIPYre+TP2vUFa3uY2UjE3o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=V5JaRGrUmgKsFenh53PLVTcWCNAKl1NB2vLxyVYinBaWGgSEFN5FULnUIocHmCZns lftjSc7ySRFu9V3xuE1aXarNkSVN7TcxHvbbJYR+1z6dvjXH+yrMiP53f12vzyQ1Vb CHekjsxnYiGfyj/MT8h2yYae02fw3lVyVRo6ufuY= Date: Mon, 30 Jun 2025 14:30:08 +0300 From: Laurent Pinchart To: Maxime Ripard Cc: Mike Looijmans , dri-devel@lists.freedesktop.org, David Airlie , Maarten Lankhorst , Michal Simek , Simona Vetter , Thomas Zimmermann , Tomi Valkeinen , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm: xlnx: zynqmp_dp: Support DRM_FORMAT_XRGB8888 Message-ID: <20250630113008.GD20333@pendragon.ideasonboard.com> References: <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.fb98a918-329e-4536-a0a5-a99b22ba0120@emailsignatures365.codetwo.com> <20250627145058.6880-1-mike.looijmans@topic.nl> <20250627181911.GF24912@pendragon.ideasonboard.com> <42af6260-c8af-42e1-a9bb-adfaaabf0190@topic.nl> <20250630-psychedelic-tested-smilodon-adcbb3@houat> <20250630091156.GE24861@pendragon.ideasonboard.com> <20250630-phenomenal-taipan-of-imagination-59b300@houat> <20250630093335.GC20333@pendragon.ideasonboard.com> <20250630-delicate-stirring-sawfly-dd81be@houat> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250630-delicate-stirring-sawfly-dd81be@houat> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250630_043036_630655_9D43363B X-CRM114-Status: GOOD ( 39.19 ) 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 Mon, Jun 30, 2025 at 12:52:48PM +0200, Maxime Ripard wrote: > On Mon, Jun 30, 2025 at 12:33:35PM +0300, Laurent Pinchart wrote: > > On Mon, Jun 30, 2025 at 11:29:08AM +0200, Maxime Ripard wrote: > > > On Mon, Jun 30, 2025 at 12:11:56PM +0300, Laurent Pinchart wrote: > > > > On Mon, Jun 30, 2025 at 10:27:55AM +0200, Maxime Ripard wrote: > > > > > On Mon, Jun 30, 2025 at 10:03:16AM +0200, Mike Looijmans wrote: > > > > > > On 27-06-2025 20:19, Laurent Pinchart wrote: > > > > > > > On Fri, Jun 27, 2025 at 04:50:46PM +0200, Mike Looijmans wrote: > > > > > > > > XRGB8888 is the default mode that Xorg will want to use. Add support > > > > > > > > for this to the Zynqmp DisplayPort driver, so that applications can use > > > > > > > > 32-bit framebuffers. This solves that the X server would fail to start > > > > > > > > unless one provided an xorg.conf that sets DefaultDepth to 16. > > > > > > > > > > > > > > > > Signed-off-by: Mike Looijmans > > > > > > > > --- > > > > > > > > > > > > > > > > drivers/gpu/drm/xlnx/zynqmp_disp.c | 5 +++++ > > > > > > > > 1 file changed, 5 insertions(+) > > > > > > > > > > > > > > > > diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c b/drivers/gpu/drm/xlnx/zynqmp_disp.c > > > > > > > > index 80d1e499a18d..501428437000 100644 > > > > > > > > --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c > > > > > > > > +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c > > > > > > > > @@ -312,6 +312,11 @@ static const struct zynqmp_disp_format avbuf_gfx_fmts[] = { > > > > > > > > .buf_fmt = ZYNQMP_DISP_AV_BUF_FMT_NL_GFX_RGBA8888, > > > > > > > > .swap = true, > > > > > > > > .sf = scaling_factors_888, > > > > > > > > + }, { > > > > > > > > + .drm_fmt = DRM_FORMAT_XRGB8888, > > > > > > > > + .buf_fmt = ZYNQMP_DISP_AV_BUF_FMT_NL_GFX_RGBA8888, > > > > > > > > + .swap = true, > > > > > > > > + .sf = scaling_factors_888, > > > > > > > > > > > > > > I'm afraid that's not enough. There's a crucial difference between > > > > > > > DRM_FORMAT_ARGB8888 (already supported by this driver) and > > > > > > > DRM_FORMAT_XRGB8888: for the latter, the 'X' component must be ignored. > > > > > > > The graphics layer is blended on top of the video layer, and the blender > > > > > > > uses both a global alpha parameter and the alpha channel of the graphics > > > > > > > layer for 32-bit RGB formats. This will lead to incorrect operation when > > > > > > > the 'X' component is not set to full opacity. > > > > > > > > > > > > I spent a few hours digging in the source code and what I could find in the > > > > > > TRM and register maps, but there's not enough information in there to > > > > > > explain how the blender works. The obvious "XRGB" implementation would be to > > > > > > just disable the blender. > > > > > > > > > > > > What I got from experimenting so far is that the alpha component is ignored > > > > > > anyway while the video path isn't active. So as long as one isn't using the > > > > > > video blending path, the ARGB and XRGB modes are identical. > > > > > > > > > > > > Guess I'll need assistance from AMD/Xilinx to completely implement the XRGB > > > > > > modes. > > > > > > > > > > > > (For our application, this patch is sufficient as it solves the issues like > > > > > > X11 not starting up, OpenGL not working and horrendously slow scaling > > > > > > performance) > > > > > > > > > > Given that we consider XRGB8888 mandatory, > > > > > > > > How about platforms that can't support it at all ? > > > > > > We emulate it. > > > > Does that imply a full memcpy of the frame buffer in the kernel driver, > > or is it emulated in userspace ? > > Neither :) > > The kernel deals with it through drm_fb_xrgb8888_to_* helpers, but only > on the parts of the framebuffer that were modified through the damage > API. Aahhh OK, it's for the fbdev emulation. So that means that drivers are not required to support XRGB8888 ? -- Regards, Laurent Pinchart