Re: [PATCH] drm/xe/display: Block hpd during suspend

[Imre Deak <imre.deak@intel.com>]

On Thu, Jul 17, 2025 at 02:24:25PM +0530, Dibin Moolakadan Subrahmanian wrote:
> It has been observed that during `xe_display_pm_suspend()` execution,
> an HPD interrupt can still be triggered, resulting in `dig_port_work`
> being scheduled. The issue arises when this work executes after
> `xe_display_pm_suspend_late()`, by which time the display is fully
> suspended.
> 
> This can lead to errors such as "DC state mismatch", as the dig_port
> work accesses display resources that are no longer available or
> powered.
> 
> To address this, introduce  'intel_hpd_block_all_encoders()' and
> 'intel_hpd_unblock_all_encoders()' functions, which iterate over all
> encoders and block/unblock HPD respectively.
> 
> These are used to:
> - Block HPD IRQs before calling 'intel_hpd_cancel_work' in suspend
> - Unblock HPD IRQs after 'intel_hpd_init' in resume
> 
> This will prevent 'dig_port_work' being scheduled during display
> suspend.
> 
> Continuation of previous patch discussion:
> https://patchwork.freedesktop.org/patch/663964/
> 
> Signed-off-by: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hotplug.c | 24 ++++++++++++++++++--
>  drivers/gpu/drm/i915/display/intel_hotplug.h |  2 ++
>  drivers/gpu/drm/xe/display/xe_display.c      |  4 ++++
>  3 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
> index 265aa97fcc75..7ffd8ded1c26 100644
> --- a/drivers/gpu/drm/i915/display/intel_hotplug.c
> +++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
> @@ -223,6 +223,28 @@ queue_detection_work(struct intel_display *display, struct work_struct *work)
>  	return queue_work(display->wq.unordered, work);
>  }
>  
> +void intel_hpd_unblock_all_encoders(struct intel_display *display)
> +{
> +	struct intel_encoder *encoder;
> +
> +	if (!HAS_DISPLAY(display))
> +		return;
> +
> +	for_each_intel_encoder(display->drm, encoder)
> +		intel_hpd_unblock(encoder);
> +}
> +
> +void intel_hpd_block_all_encoders(struct intel_display *display)
> +{
> +	struct intel_encoder *encoder;
> +
> +	if (!HAS_DISPLAY(display))
> +		return;
> +
> +	for_each_intel_encoder(display->drm, encoder)
> +		intel_hpd_block(encoder);
> +}

intel_encoder.c has the intel_encoder_{suspend,shutdown}_all() helpers
called in the same suspend/shutdown paths, so I'd also add these to there
calling them stg like intel_encoder_{block,unblock}_all_hpds().

> +
>  static void
>  intel_hpd_irq_storm_switch_to_polling(struct intel_display *display)
>  {
> @@ -971,8 +993,6 @@ void intel_hpd_cancel_work(struct intel_display *display)
>  
>  	spin_lock_irq(&display->irq.lock);
>  
> -	drm_WARN_ON(display->drm, get_blocked_hpd_pin_mask(display));
> -
>  	display->hotplug.long_hpd_pin_mask = 0;
>  	display->hotplug.short_hpd_pin_mask = 0;
>  	display->hotplug.event_bits = 0;
> diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.h b/drivers/gpu/drm/i915/display/intel_hotplug.h
> index edc41c9d3d65..3938c93d2385 100644
> --- a/drivers/gpu/drm/i915/display/intel_hotplug.h
> +++ b/drivers/gpu/drm/i915/display/intel_hotplug.h
> @@ -34,5 +34,7 @@ void intel_hpd_debugfs_register(struct intel_display *display);
>  void intel_hpd_enable_detection_work(struct intel_display *display);
>  void intel_hpd_disable_detection_work(struct intel_display *display);
>  bool intel_hpd_schedule_detection(struct intel_display *display);
> +void intel_hpd_block_all_encoders(struct intel_display *display);
> +void intel_hpd_unblock_all_encoders(struct intel_display *display);
>  
>  #endif /* __INTEL_HOTPLUG_H__ */
> diff --git a/drivers/gpu/drm/xe/display/xe_display.c b/drivers/gpu/drm/xe/display/xe_display.c
> index e2e0771cf274..51584ea3ed09 100644
> --- a/drivers/gpu/drm/xe/display/xe_display.c
> +++ b/drivers/gpu/drm/xe/display/xe_display.c
> @@ -340,6 +340,8 @@ void xe_display_pm_suspend(struct xe_device *xe)
>  
>  	xe_display_flush_cleanup_work(xe);
>  
> +	intel_hpd_block_all_encoders(display);
> +

Yes, I still think blocking here only the HPD IRQs makes sense,
disabling all the display IRQs suggested by Maarten only later.

xe_display_pm_shutdown() also misses this.

Also xe_display_fini_early() - which is called after disabling all IRQs
- misses intel_hpd_cancel_work().

>  	intel_hpd_cancel_work(display);
>  
>  	if (has_display(xe)) {
> @@ -471,6 +473,8 @@ void xe_display_pm_resume(struct xe_device *xe)
>  
>  	intel_hpd_init(display);
>  
> +	intel_hpd_unblock_all_encoders(display);
> +
>  	if (has_display(xe)) {
>  		intel_display_driver_resume(display);
>  		drm_kms_helper_poll_enable(&xe->drm);
> -- 
> 2.43.0
>