[Bug 82593] [BYT]udevadm unable to monitor HDMI plug/unplug event sporadically

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=82593

--- Comment #2 from Guo Jinxian <jinxianx.guo at intel.com> ---
Created attachment 106403
  --> https://bugs.freedesktop.org/attachment.cgi?id=106403&action=edit
dmesg

(In reply to comment #1)
> Please enable drm.debug=0xf to get drm core debugging, *or* apply this patch
> to debug the hotplug events:
> 
> diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> index ab1a5f6dde8a..6abf092d9eb4 100644
> --- a/drivers/gpu/drm/drm_sysfs.c
> +++ b/drivers/gpu/drm/drm_sysfs.c
> @@ -481,7 +481,7 @@ void drm_sysfs_hotplug_event(struct drm_device *dev)
>  	char *event_string = "HOTPLUG=1";
>  	char *envp[] = { event_string, NULL };
>  
> -	DRM_DEBUG("generating hotplug event\n");
> +	DRM_DEBUG_KMS("generating hotplug event\n");
>  
>  	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
>  }
> 
> Now, doing hotplug and looking at both udevadm monitor and dmesg, do you see
> cases where:
> 
> a) there's the "generating hotplug event" in dmesg, but you do *not* get it
> in udevadm monitor
> 
> *or*
> 
> b) you do hotplug but the message is not in dmesg and you don't get it in
> udevadm either.

Enable drm.debug=0xf, then doing hotplug, the result is case a):the hotplug
event is able to catch by dmesg, and not catch by udevadm monitor.

Dmesg info
[  216.014284] [drm:intel_hpd_irq_handler] hotplug event received, stat
0x00040000, dig 0x00000000
[  216.014307] [drm:intel_hpd_irq_handler] digital hpd port B - short
[  216.014389] [drm:intel_dp_hpd_pulse] got hpd irq on port B - short
[  233.419105] [drm:intel_hpd_irq_handler] hotplug event received, stat
0x00040000, dig 0x00000000
[  233.419130] [drm:intel_hpd_irq_handler] digital hpd port B - short
[  233.419172] [drm:intel_dp_hpd_pulse] got hpd irq on port B - short

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