Re: [PATCH 1/2] arm64: dts: qcom: hamoa-iot-evk: Add eDP display overlay

[Anand Tiwari <anand.tiwari@oss.qualcomm.com>]

On Mon, Aug 10, 2026 at 12:04:21PM +0300, Dmitry Baryshkov wrote:
> On Fri, Aug 07, 2026 at 03:30:13PM +0530, Anand Tiwari wrote:
> > On Thu, Aug 06, 2026 at 07:05:37PM -0500, Bjorn Andersson wrote:
> > > On Thu, Aug 06, 2026 at 10:01:20PM +0530, Anand Tiwari wrote:
> > > > Move the eDP panel configuration and related power, backlight, and pinctrl
> > > > nodes into a separate overlay. Keep the base DTB suitable for headless
> > > > variants and provide a composite DTB for headed variants.
> > > 
> > > To quote:
> > > https://docs.kernel.org/process/submitting-patches.html#describe-your-changes
> > > 
> > > """
> > > Describe your problem. Whether your patch is a one-line bug fix or 5000
> > > lines of a new feature, there must be an underlying problem that
> > > motivated you to do this work. Convince the reviewer that there is a
> > > problem worth fixing and that it makes sense for them to read past the
> > > first paragraph.
> > > """
> > > 
> > > In fact, I'm not even able to guess what the problem you're fixing here.
> > > 
> > > Regards,
> > > Bjorn
> > >
> > 
> > The problem is that the base device trees currently describe the eDP
> > display hardware unconditionally. However, Hamoa and Purwa IoT EVKs
> > are also available in headless variants without an eDP panel.
> > 
> > With current base DTBs, headless variants are not stable where eDP panel is not
> > physically connected with board and userspace is trying to use it.
> 
> Please define "are not stable"

I did not see any crash in this case but in the absence of physical panel 
logs are flooded with errors, userspace is trying to commit the frames 
since connector status is always connected:

"
[   23.499621] panel-simple-dp-aux aux-aea0000.displayport-controller: Prepare 
timeout after 5 tries
[   23.508763] panel-simple-dp-aux aux-aea0000.displayport-controller: 
Couldn't power on panel to ID it; using conservative timings: -110
[   52.143157] [drm:dpu_kms_wait_for_commit_done:525] [dpu error]wait for 
commit done returned -110
[   52.175662] [drm:dpu_encoder_frame_done_timeout:2733] [dpu error]enc40 
frame done timeout
[   55.351084] [drm:dpu_encoder_helper_report_irq_timeout [msm]] *ERROR* 
irq timeout id=40, intf_mode=INTF_MODE_VIDEO intf=5 wb=-1, pp=0, intr=0
"
 
Another issue On Ubuntu with Gnome Desktop is:
Display's connected with other DP ports are only showing backlight since 
login UI picked eDP panel connector which is not physically connected.

> 
> > This series fixes the inaccurate hardware description by keeping the
> > base DTBs limited to hardware common to both variants and moving the
> > eDP-specific nodes into separate overlays. The base DTB can therefore
> > be used for headless variants, while the overlay is selected for
> > headed variants.
> 
> -- 
> With best wishes
> Dmitry