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 AE13FC7EE39 for ; Mon, 30 Jun 2025 09:39:31 +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=Tnx15OyMGSN2+mZlMjFEwv4ImpI6il79Opc7x7K8jMo=; b=s6Y3zqym2bcTlkKZfdJhiLLp4h vGiOVoXGhs/ag+ftpZjEN2xEY6bYdwfHDdUTsxNqnjqMEjwelNwOYXwaFubJ1b/aEvjobvOP28FKn 5dliuVT5Mz+VOQc8ptDmVXZKAaa52Rjbl32J7rIFRCCPdTyGPgeXVGrxd2IxK1CmrakOnnBo03fJQ 9C+bM+3V+KGk0uBpW6Sh5hPeRCVRwF/3xZcmnf3e2V+7At/6cLOkYTpbHYbYEEmI+IpZCP6hTIC9L LArYaEJnfvtEdO74T/iAOe2EyCcM+n3mn5LmeNCmHV5u7PFUO+/J6PXmheVYSOxGGwzL/M4ueF97r oMN1oOkQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uWAyy-00000001lwe-0BYn; Mon, 30 Jun 2025 09:39:24 +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 1uWAtn-00000001lHx-0etQ for linux-arm-kernel@lists.infradead.org; Mon, 30 Jun 2025 09:34:04 +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 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250630_023403_332920_73D26BD3 X-CRM114-Status: GOOD ( 39.95 ) 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 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