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 BA229C7EE39 for ; Mon, 30 Jun 2025 09:34:03 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1D87F10E21A; Mon, 30 Jun 2025 09:34:03 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="O4fKiMhe"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id CAEC510E21A for ; Mon, 30 Jun 2025 09:34:01 +0000 (UTC) Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id B7672EFF; Mon, 30 Jun 2025 11:33:38 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1751276018; bh=i2H7wxuvjKrprsdjJQ79FfENDYU2gTxNL+H4wIq0OH0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=O4fKiMherV54uzy8RutgjMV0OtIp04hwC+DMxJkG42JHGNI8cF/uHsRS9l6o3niDD s5Ea8f07ZdnnnkZ4NyavKg289o/DF+vnJqdkPJnS1W+zdp8gkXjcbcDN8F9KxVVQJP QJcp2IzhJYO+z6uvzjg1H8pja1S8OAU383ewUuP8= Date: Mon, 30 Jun 2025 12:33:35 +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: <20250630093335.GC20333@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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250630-phenomenal-taipan-of-imagination-59b300@houat> 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, 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 ? > > > this patch is a good thing to > > > have anyway, even if suboptimal, or broken in some scenario we can > > > always fix later. > > > > It needs to at least be updated to disallow XRGB8888 usage when the > > video plan is enabled, or when global alpha is set to a non-opaque > > value. > > Yeah, that's reasonable -- Regards, Laurent Pinchart