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

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

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:

Reviewed-by: Imre Deak <imre.deak@intel.com>

>  	intel_dp_mst_suspend(display);
>  	intel_hpd_cancel_work(display);
>  
> @@ -471,6 +475,8 @@ void xe_display_pm_resume(struct xe_device *xe)
>  
>  	intel_hpd_init(display);
>  
> +	intel_encoder_unblock_all_hpds(display);
> +
>  	if (has_display(xe)) {
>  		intel_display_driver_resume(display);
>  		drm_kms_helper_poll_enable(&xe->drm);
> -- 
> 2.43.0
>