Re: [PATCH 0/2] drm: xlnx: zynqmp_kms: 16 bpp fixes for Xorg startup on AMD KV260

Tomi Valkeinen
2026-01-06T08:29:43Z

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.

Tomi