Re: [PATCH v5 00/10] drm/msm/dp: Drop the HPD state machine

[Val Packett <val@packett.cool>]

On 3/13/26 10:09 PM, Dmitry Baryshkov wrote:
> Currently, all HPD interrupt handling must go through the HPD state
> machine.
>
> This has caused many issues where the DRM framework assumes that DP is
> in one state while the state machine is stuck in another state.
>
> As discussed here [1], this series:
>
> - Removes the state machine
> - Moves link training to atomic_enable()
> - Changes the detect() behavior to return true if a display is physically
>    plugged in (as opposed to if the DP link is ready).
> - Remove event queue and move internal HPD handling to hpd_notify()
>
> To correctly detect the displays which are plugged on boot on the boards
> which use dp-connector devices, this series depends on [2]. USB-C and
> eDP panels are handled natively.
>
> [1] https://patchwork.freedesktop.org/patch/656312/?series=142010&rev=2#comment_1201738
> [2] https://lore.kernel.org/all/20260314-dp-connector-hpd-v1-0-786044cedc17@oss.qualcomm.com/

Unfortunately this currently seems to mostly break link training with 
USB-C, on x1e80100-dell-latitude-7455:

[  102.190083] [drm:msm_dp_ctrl_link_train_1_2 [msm]] *ERROR* link 
training #2 on phy 1 failed. ret=-110
[  102.192846] [drm:msm_dp_ctrl_setup_main_link [msm]] *ERROR* link 
training of LTTPR(s) failed. ret=-110
[  102.211095] [drm:msm_dp_bridge_atomic_enable [msm]] *ERROR* Failed 
link training (rc=-104)
[  102.211164] [drm:msm_dp_aux_isr [msm]] *ERROR* Unexpected DP AUX IRQ 
0x01000000 when not busy
[  102.247168] [drm:msm_dp_ctrl_link_train_1_2 [msm]] *ERROR* link 
training #2 on phy 1 failed. ret=-110
[  102.252859] [drm:msm_dp_ctrl_setup_main_link [msm]] *ERROR* link 
training of LTTPR(s) failed. ret=-110


Once I did get it to connect on one of the ports, but then on unplug it 
didn't detect the unplug properly and continued trying to use the link:

[ 1418.418954] disp_cc_mdss_dptx1_link_clk status stuck at 'off'
<trace cut>
[ 1418.420950] Failed to enable clk 'ctrl_link': -16
[ 1418.420959] [drm:msm_dp_ctrl_enable_mainlink_clocks [msm]] *ERROR* 
Unable to start link clocks. ret=-16
[ 1418.421058] [drm:msm_dp_bridge_atomic_enable [msm]] *ERROR* Failed 
link training (rc=-16)
<trace cut>
[ 1418.423228] Failed to enable clk 'ctrl_link': -16
[ 1418.423234] [drm:msm_dp_ctrl_enable_mainlink_clocks [msm]] *ERROR* 
Unable to start link clocks. ret=-16
[ 1418.423325] [drm:msm_dp_ctrl_on_stream [msm]] *ERROR* Failed to start 
link clocks. ret=-16
[ 1418.476234] [drm:dpu_encoder_phys_vid_wait_for_commit_done:543] [dpu 
error]vblank timeout: 808208c0
[ 1418.476272] [drm:dpu_kms_wait_for_commit_done:527] [dpu error]wait 
for commit done returned -110
[ 1418.509204] [drm:dpu_encoder_frame_done_timeout:2731] [dpu 
error]enc37 frame done timeout
[ 1419.163337] [drm:dpu_encoder_phys_vid_wait_for_commit_done:543] [dpu 
error]vblank timeout: 808208c0
[ 1419.163365] [drm:dpu_kms_wait_for_commit_done:527] [dpu error]wait 
for commit done returned -110

But after reboot, link training was failing on both ports..


Thanks,
~val