From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DCF2020E032 for ; Mon, 30 Jun 2025 09:12:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751274745; cv=none; b=NSv1TurAbcqL09ifBHDqTwk2guv6qgeC6Y59RSEdkWmRYHhp3MwpQ6e3vJGrrDbwQ/4iPDSptSnbt5BxWhiDLn9MJ20MikcNRwBhnJ38wHkDnm8T5JTMZW3Al3zK2IMPHWjtC6x9ovGsT1gOrKg8BhinWi1FwrfoL5HqubzFGcM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751274745; c=relaxed/simple; bh=Xk1VTz99oaXPXWle19G2zMHoIPpOeSvs6Qc/pVHBAnA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BxL1mwqSY3t15DeBDR2nGYdOcLr4aLdLzyK/dLvtlcgYK67h8nrG9dxYVkv0UcJ+imo6sRU2+0fikt9bl2Jzn1rlCD4gH08Q+hNcujh9KXvqjad3DQKXJKxJqdFOp50zWhx/dtbzFKNKW8XoJ0ARld1+1Q71EOqt8G9kN2wl/TE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=EsKha93m; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="EsKha93m" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 1CA20EFF; Mon, 30 Jun 2025 11:12:00 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1751274720; bh=Xk1VTz99oaXPXWle19G2zMHoIPpOeSvs6Qc/pVHBAnA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EsKha93mqQrmPtUWxFH2IC0l8vxECmEaf2z03chq8Hrcd4Vt7rjcbA1BKUrT05/JQ fbXrMTGnuNulIzMcsMqYEtud0xn+ApPjs8jGMut1pvsAnAoWGo9mJmvA5b0X/OCla1 qS76F+yZW/A4HkTwqCsliyLT+Vyvp+BZrQCRQWZM= Date: Mon, 30 Jun 2025 12:11:56 +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: <20250630091156.GE24861@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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250630-psychedelic-tested-smilodon-adcbb3@houat> 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 ? > 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. -- Regards, Laurent Pinchart