Re: [PATCH v2] drm/xe/display: Block hpd during suspend

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Tue, Jul 29, 2025 at 12:44:47PM +0300, Jani Nikula wrote:
> On Thu, 24 Jul 2025, Maarten Lankhorst <maarten.lankhorst@linux.intel.com> wrote:
> > Hey,
> >
> > Den 2025-07-23 kl. 15:19, skrev Rodrigo Vivi:
> >> On Wed, Jul 23, 2025 at 12:38:08PM +0300, Imre Deak wrote:
> >>> On Wed, Jul 23, 2025 at 02:59:46PM +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_encoder_block_all_hpds' and
> >>>> 'intel_encoder_unblock_all_hpds' 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
> >>>>   and shutdown
> >>>> - 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/
> >>>>
> >>>> Changes in v2:
> >>>>  - Add 'intel_encoder_block_all_hpds' to 'xe_display_pm_shutdown'
> >>>>  - Add 'intel_hpd_cancel_work' to 'xe_display_fini_early' to cancel
> >>>>    any HPD pending work at late driver removal
> >>>>
> >>>> Signed-off-by: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>
> >>>> ---
> >>>>  drivers/gpu/drm/i915/display/intel_encoder.c | 23 ++++++++++++++++++++
> >>>>  drivers/gpu/drm/i915/display/intel_encoder.h |  3 +++
> >>>>  drivers/gpu/drm/i915/display/intel_hotplug.c |  2 --
> >>>>  drivers/gpu/drm/xe/display/xe_display.c      |  6 +++++
> >>>>  4 files changed, 32 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/i915/display/intel_encoder.c b/drivers/gpu/drm/i915/display/intel_encoder.c
> >>>> index 0b7bd26f4339..4e2b77b87678 100644
> >>>> --- a/drivers/gpu/drm/i915/display/intel_encoder.c
> >>>> +++ b/drivers/gpu/drm/i915/display/intel_encoder.c
> >>>> @@ -8,6 +8,7 @@
> >>>>  #include "intel_display_core.h"
> >>>>  #include "intel_display_types.h"
> >>>>  #include "intel_encoder.h"
> >>>> +#include "intel_hotplug.h"
> >>>>  
> >>>>  static void intel_encoder_link_check_work_fn(struct work_struct *work)
> >>>>  {
> >>>> @@ -37,6 +38,28 @@ void intel_encoder_link_check_queue_work(struct intel_encoder *encoder, int dela
> >>>>  			 &encoder->link_check_work, msecs_to_jiffies(delay_ms));
> >>>>  }
> >>>>  
> >>>> +void intel_encoder_unblock_all_hpds(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_encoder_block_all_hpds(struct intel_display *display)
> >>>> +{
> >>>> +	struct intel_encoder *encoder;
> >>>> +
> >>>> +	if (!HAS_DISPLAY(display))
> >>>> +		return;
> >>>> +
> >>>> +	for_each_intel_encoder(display->drm, encoder)
> >>>> +		intel_hpd_block(encoder);
> >>>> +}
> >>>> +
> >>>>  void intel_encoder_suspend_all(struct intel_display *display)
> >>>>  {
> >>>>  	struct intel_encoder *encoder;
> >>>> diff --git a/drivers/gpu/drm/i915/display/intel_encoder.h b/drivers/gpu/drm/i915/display/intel_encoder.h
> >>>> index 3fa5589f0b1c..e1d3aeab7c00 100644
> >>>> --- a/drivers/gpu/drm/i915/display/intel_encoder.h
> >>>> +++ b/drivers/gpu/drm/i915/display/intel_encoder.h
> >>>> @@ -17,4 +17,7 @@ void intel_encoder_link_check_flush_work(struct intel_encoder *encoder);
> >>>>  void intel_encoder_suspend_all(struct intel_display *display);
> >>>>  void intel_encoder_shutdown_all(struct intel_display *display);
> >>>>  
> >>>> +void intel_encoder_block_all_hpds(struct intel_display *display);
> >>>> +void intel_encoder_unblock_all_hpds(struct intel_display *display);
> >>>> +
> >>>>  #endif /* __INTEL_ENCODER_H__ */
> >>>> diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
> >>>> index 265aa97fcc75..c69b535497bf 100644
> >>>> --- a/drivers/gpu/drm/i915/display/intel_hotplug.c
> >>>> +++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
> >>>> @@ -971,8 +971,6 @@ 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/xe/display/xe_display.c b/drivers/gpu/drm/xe/display/xe_display.c
> >>>> index e2e0771cf274..9e984a045059 100644
> >>>> --- a/drivers/gpu/drm/xe/display/xe_display.c
> >>>> +++ b/drivers/gpu/drm/xe/display/xe_display.c
> >>>> @@ -96,6 +96,7 @@ static void xe_display_fini_early(void *arg)
> >>>>  	if (!xe->info.probe_display)
> >>>>  		return;
> >>>>  
> >>>> +	intel_hpd_cancel_work(display);
> >>>>  	intel_display_driver_remove_nogem(display);
> >>>>  	intel_display_driver_remove_noirq(display);
> >>>>  	intel_opregion_cleanup(display);
> >>>> @@ -340,6 +341,8 @@ void xe_display_pm_suspend(struct xe_device *xe)
> >>>>  
> >>>>  	xe_display_flush_cleanup_work(xe);
> >>>>  
> >>>> +	intel_encoder_block_all_hpds(display);
> >>>> +
> >>>>  	intel_hpd_cancel_work(display);
> >>>>  
> >>>>  	if (has_display(xe)) {
> >>>> @@ -369,6 +372,7 @@ void xe_display_pm_shutdown(struct xe_device *xe)
> >>>>  	}
> >>>>  
> >>>>  	xe_display_flush_cleanup_work(xe);
> >>>> +	intel_encoder_block_all_hpds(display);
> >>>
> >>> MST still needs HPD IRQs for side-band messaging, so the HPD IRQs must
> >>> be blocked only after intel_dp_mst_suspend().
> >>>
> >>> Otherwise the patch looks ok to me, so with the above fixed and provided
> >>> that Maarten is ok to disable all display IRQs only later:
> >> 
> >> Also probably good to identify the patch as both xe and i915 in the subject
> >> drm/{i915,xe}/display:
> >> 
> >> and Maarten or Imre, any preference on which branch to go? any chance of
> >> conflicting with any of work you might be doing in any side?
> >> 
> >> From my side I believe that any conflict might be easy to handle, so
> >> 
> >> Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> >> 
> >> from either side...
> >> 
> >>>
> >>> Reviewed-by: Imre Deak <imre.deak@intel.com>
> > We had a discussion on this approach, and it seems that completely disabling interrupts here like in i915 would fail too.
> >
> > Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >
> > I don't mind either branch. As long as it applies. :-)
> 
> Please do not merge through *any* tree.
> 
> How come you all think it's okay to add this xe specific thing, and make
> unification harder?

I lost any moral or rights to complain here since I couldn't move with my
tasks of unification of the pm flow :(

double sorry!

> 
> intel_encoder_block_all_hpds() is *way* too specific for a high level
> function. Neither xe nor i915 should never call something like that
> directly.

that's a valid point indeed. But I cannot see another way to fix the
current issue right now without trying to move with the full unification
faster. Do you?

> 
> 
> BR,
> Jani.
> 
> 
> -- 
> Jani Nikula, Intel