Hi
Am 07.01.26 um 09:00 schrieb Mikko Rapeli:
Hi,
On Tue, Jan 06, 2026 at 10:29:37AM +0200, Tomi Valkeinen wrote:
Hi,
On 06/01/2026 09:41, Thomas Zimmermann wrote:
Hi
Am 22.12.25 um 09:58 schrieb Mikko Rapeli:
Hi,
On Fri, Dec 19, 2025 at 02:30:11PM +0200, Mikko Rapeli wrote:
On Fri, Dec 19, 2025 at 01:59:14PM +0200, Tomi Valkeinen wrote:
On 05/12/2025 14:37, Mikko Rapeli wrote:
Currently on default yocto images Xorg fails to start on AMD KV260
because 24/32 color depth gets detected but does not actually work.
These two patches fix the issue and now 16 bpp gets detected
and Xorg starts and draws on external HDMI display using
kernel.org based linux-yocto kernel.
Anatoliy Klymenko (1):
drm: xlnx: zynqmp_kms: Init fbdev with 16 bit color
Mikko Rapeli (1):
drm: xlnx: zynqmp_kms: set preferred_depth to 16 bpp
drivers/gpu/drm/xlnx/zynqmp_kms.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
Did you notice the few already sent serieses on the list where the
topic
has been discussed?
[PATCH] drm: xlnx: zynqmp_dp: Support DRM_FORMAT_XRGB8888
[PATCH 0/3] drm: zynqmp: Make the video plane primary
Oh I wasn't aware of these.
Or is there something else on KV260 that messes up the 24 bit color?
These look very similar and likely fix the X11 startup. I will give them
a try.
Right, now I've tested:
* these patches from Anatoliy and me to help X11 use 16bpp mode by
default
and removes the need to manually setup Xorg for 16bpp
* "drm: xlnx: zynqmp_dp: Support DRM_FORMAT_XRGB8888" which enables
the X11 default
24bpp to work, no need to set Xorg config to 16bpp
* "drm: zynqmp: Make the video plane primary" which also fixes the
X11 default
24bpp to work, no need to set Xorg config to 16bpp
All of these fix HDMI graphics output on AMD KV260 board with yocto
genericarm64 machine
and core-image-sato image which includes Xorg. The graphics rendering
is still
very slow but I think that is a different problem.
I guess the last series from Sean Anderson is moving forward so I'll
reply to that thread separately.
Just want to say that the series here improves xlnx and makes it a
'better' driver. IMHO the changes should be merged independently from
what happens with the other series.
I might be missing something, but I don't think I fully agree. Yes, the
userspace doesn't seem to be able to cope with the current upstream
driver behavior (even if it's not wrong as such, afaics), so in that
sense this series is better. But I don't think (almost) anyone really
wants to use RGB565 if XRGB8888 is an option? And that's what the other
series is trying to achieve, and that series conflicts with this one.
So I'd rather try to get a conclusion on Sean's series (or the other one
from Mike). If that effort fails, we could go with this series as a backup.
I did testing of all three different patch series'es on AMD KV260 and
did not find any performance difference between them. The Xorg
rendering is still very slow to an external HDMI display.
I don't have an opinion on the graphics formats but just want something
out to a display by default. I think there is a lot more to fix to get
the performance into usable state.
I briefly looked through the xlnx driver and found several things to try.
* The update code in [1] appears to always update the whole buffer.
Setting drm_plane_enable_fb_damage_clips() for the planes will enable
damage handling. Then flushing only the damaged areas might improve
performance.
* The driver could set drm_device.mode_config.prefer_shadow to make Xorg
use a shadow buffer in user space. This often works for devices with
discrete VRAM. IDK if non-X compositors also benefit from this.
* If the hardware supports it, setting non-coherent DMA mappings could
enable caching on the memory buffers. The driver would then have to
enable damage clips and flush caches by itself where necessary.
Best regards
Thomas
[1]
https://elixir.bootlin.com/linux/v6.18.3/source/drivers/gpu/drm/xlnx/zynqmp_disp.c#L1109
Cheers,
-Mikko
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
