drm/{i915,xe}/display: Block hpd during suspend

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'.(Imre
Deak)
- Add 'intel_hpd_cancel_work' to 'xe_display_fini_early' to cancel
any HPD pending work at late driver removal. (Imre Deak)

Changes in v3:
- Move 'intel_encoder_block_all_hpds' after intel_dp_mst_suspend
in 'xe_display_pm_shutdown'.(Imre Deak)

Signed-off-by: Dibin Moolakadan Subrahmanian <[e-mail]>
Reviewed-by: Imre Deak <[e-mail]>
Reviewed-by: Maarten Lankhorst <[e-mail]>
Acked-by: Jani Nikula <[e-mail]>
Acked-by: Rodrigo Vivi <[e-mail]>
Signed-off-by: Imre Deak <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/i915/display/intel_encoder.c

···
 #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)
 {
···
 
 	mod_delayed_work(display->wq.unordered,
 			 &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)

drivers/gpu/drm/i915/display/intel_encoder.h

···
 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__ */

drivers/gpu/drm/i915/display/intel_hotplug.c

···
 
 	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;

drivers/gpu/drm/xe/display/xe_display.c

···
 	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);
···
 
 	xe_display_flush_cleanup_work(xe);
 
+	intel_encoder_block_all_hpds(display);
+
 	intel_hpd_cancel_work(display);
 
 	if (has_display(xe)) {
···
 
 	xe_display_flush_cleanup_work(xe);
 	intel_dp_mst_suspend(display);
+	intel_encoder_block_all_hpds(display);
 	intel_hpd_cancel_work(display);
 
 	if (has_display(xe))
···
 		intel_display_driver_resume_access(display);
 
 	intel_hpd_init(display);
+
+	intel_encoder_unblock_all_hpds(display);
 
 	if (has_display(xe)) {
 		intel_display_driver_resume(display);