linux-kernel - Re: [PATCH 0/3] drm: zynqmp: Make the video plane primary

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Message-ID: <aUkSclVzlRCXDdug@nuoska>
Date: Mon, 22 Dec 2025 11:42:10 +0200
From: Mikko Rapeli <mikko.rapeli@...aro.org>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Mike Looijmans <mike.looijmans@...ic.nl>,
	David Airlie <airlied@...il.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Anatoliy Klymenko <anatoliy.klymenko@....com>,
	Maxime Ripard <mripard@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	Simona Vetter <simona@...ll.ch>,
	Michal Simek <michal.simek@....com>
Subject: Re: [PATCH 0/3] drm: zynqmp: Make the video plane primary

Hi,

On Thu, Nov 13, 2025 at 03:37:11PM -0500, Sean Anderson wrote:
> The graphics plane does not support XRGB8888, which is the default mode
> X uses for 24-bit color. Because of this, X must be set to use 16-bit
> color, which has a measurable performance penalty. Make the video plane
> the primary plane as it natively supports XRGB8888. An alternative
> approach to add XRGB8888 to the graphics plane is discussed in [1], as
> well as in patch 2.
> 
> [1] https://lore.kernel.org/dri-devel/20250627145058.6880-1-mike.looijmans@topic.nl/

I've tested this series on AMD KV260 running Yocto genericarm64 machine config and
core-image-sato with Xorg. This series fixes HDMI output using X11, no need to
configure Xorg to 16bpp as workaround.

Tested-by: Mikko Rapeli <mikko.rapeli@...aro.org>

That said, I also tested
https://lore.kernel.org/dri-devel/20250627145058.6880-1-mike.looijmans@topic.nl/
and it works.

And I tested and submitted the patch for zynqmp framebuffer to prefer 16bpp
until different modes are actually support, which fixes Xorg startup and
the depth detection logic used there:

https://lore.kernel.org/dri-devel/20251205123751.2257694-3-mikko.rapeli@linaro.org/

This series and Mike's patches enable 24bpp mode to work, which I guess is the long
term path, but it is not clear to me what is still missing.

The patch from me fixes the current situtation where only 16bpp works but framebuffer
driver does not prefer that and thus userspace X11 uses the default 24bpp
which then fails. My patch could be merged right now until the XRGB8888 support
is finalized.

Cheers,

-Mikko