Re: [PATCH v5 3/6] drm/i915/hpd: Add support for blocking the IRQ handling on an HPD pin

[Jani Nikula <jani.nikula@intel.com>]

On Tue, 04 Mar 2025, Imre Deak <imre.deak@intel.com> wrote:
> Add support for blocking the IRQ handling on the HPD pin of a given
> encoder, handling IRQs that arrived while in the blocked state after
> unblocking the IRQ handling. This will be used by a follow-up change,
> which blocks/unblocks the IRQ handling around DP link training.
>
> This is similar to the intel_hpd_disable/enable() functionality, by also
> handling encoders/ports with a pulse handler (i.e. also
> blocking/unblocking the short/long pulse handling) and handling the IRQs
> arrived in the blocked state after the handling is unblocked (vs. just
> dropping such IRQs).
>
> v2:
> - Handle encoders without a port assigned to them.
> - Fix clearing IRQs from intel_hotplug::short_port_mask.
> v3:
> - Rename intel_hpd_suspend/resume() to intel_hpd_block/unblock(). (Jani)
> - Refer to HPD pins as hpd_pin vs. hpd.
> - Flush dig_port_work in intel_hpd_block() if any encoder using the HPD
>   pin has a pulse handler.
> v4:
> - Fix hpd_pin_has_pulse(), checking the encoder's HPD pin.
> v5:
> - Rebase on port->hpd_pin tracking. (Ville)
>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  .../gpu/drm/i915/display/intel_display_core.h |   1 +
>  drivers/gpu/drm/i915/display/intel_hotplug.c  | 205 +++++++++++++++---
>  drivers/gpu/drm/i915/display/intel_hotplug.h  |   2 +
>  3 files changed, 183 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h b/drivers/gpu/drm/i915/display/intel_display_core.h
> index d9952007635e0..fbe890775c2ab 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_core.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_core.h
> @@ -159,6 +159,7 @@ struct intel_hotplug {
>  	struct {
>  		unsigned long last_jiffies;
>  		int count;
> +		int blocked_count;
>  		enum {
>  			HPD_ENABLED = 0,
>  			HPD_DISABLED = 1,
> diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
> index 3fb5feeefa144..cb4e320a1023d 100644
> --- a/drivers/gpu/drm/i915/display/intel_hotplug.c
> +++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
> @@ -349,19 +349,56 @@ static bool intel_encoder_has_hpd_pulse(struct intel_encoder *encoder)
>  		enc_to_dig_port(encoder)->hpd_pulse != NULL;
>  }
>  
> +static bool hpd_pin_has_pulse(struct intel_display *display, enum hpd_pin pin)
> +{
> +	struct intel_encoder *encoder;
> +
> +	for_each_intel_encoder(display->drm, encoder) {
> +		if (encoder->hpd_pin != pin)
> +			continue;
> +
> +		if (intel_encoder_has_hpd_pulse(encoder))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +static u32 get_blocked_hpd_pins(struct intel_display *display)

Nitpick, I kinda dislike this _pins and _bits
naming. get_blocked_hpd_pin_mask seems better since you'll do bit ops
with long_hpd_pin_mask and short_hpd_pin_mask.

> +{
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +	enum hpd_pin pin;
> +	u32 hpd_pins = 0;
> +
> +	lockdep_assert_held(&i915->irq_lock);
> +
> +	for_each_hpd_pin(pin) {
> +		if (display->hotplug.stats[pin].blocked_count)
> +			hpd_pins |= BIT(pin);
> +	}
> +
> +	return hpd_pins;
> +}
> +
>  static void i915_digport_work_func(struct work_struct *work)
>  {
> -	struct drm_i915_private *dev_priv =
> -		container_of(work, struct drm_i915_private, display.hotplug.dig_port_work);
> +	struct intel_display *display =
> +		container_of(work, struct intel_display, hotplug.dig_port_work);
> +	struct drm_i915_private *dev_priv = to_i915(display->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
>  	u32 long_hpd_pin_mask, short_hpd_pin_mask;
>  	struct intel_encoder *encoder;
> +	u32 blocked_hpd_pins;
>  	u32 old_bits = 0;
>  
>  	spin_lock_irq(&dev_priv->irq_lock);
> -	long_hpd_pin_mask = dev_priv->display.hotplug.long_hpd_pin_mask;
> -	dev_priv->display.hotplug.long_hpd_pin_mask = 0;
> -	short_hpd_pin_mask = dev_priv->display.hotplug.short_hpd_pin_mask;
> -	dev_priv->display.hotplug.short_hpd_pin_mask = 0;
> +
> +	blocked_hpd_pins = get_blocked_hpd_pins(display);

Ditto here, blocked_hpd_pin_mask seems more clear to me.

> +	long_hpd_pin_mask = hotplug->long_hpd_pin_mask & ~blocked_hpd_pins;
> +	hotplug->long_hpd_pin_mask &= ~long_hpd_pin_mask;
> +	short_hpd_pin_mask = hotplug->short_hpd_pin_mask & ~blocked_hpd_pins;
> +	hotplug->short_hpd_pin_mask &= ~short_hpd_pin_mask;
> +
>  	spin_unlock_irq(&dev_priv->irq_lock);
>  
>  	for_each_intel_encoder(&dev_priv->drm, encoder) {
> @@ -406,14 +443,18 @@ static void i915_digport_work_func(struct work_struct *work)
>   */
>  void intel_hpd_trigger_irq(struct intel_digital_port *dig_port)
>  {
> -	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
> +	struct intel_display *display = to_intel_display(dig_port);
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
>  	struct intel_encoder *encoder = &dig_port->base;
>  
>  	spin_lock_irq(&i915->irq_lock);
> -	i915->display.hotplug.short_hpd_pin_mask |= BIT(encoder->hpd_pin);
> -	spin_unlock_irq(&i915->irq_lock);
>  
> -	queue_work(i915->display.hotplug.dp_wq, &i915->display.hotplug.dig_port_work);
> +	hotplug->short_hpd_pin_mask |= BIT(encoder->hpd_pin);
> +	if (!(BIT(encoder->hpd_pin) & get_blocked_hpd_pins(display)))

Maybe add a helper hpd_pin_is_blocked()? It could access
hotplug->stats[pin].blocked_count directly without iterating all of
them.

> +		queue_work(hotplug->dp_wq, &hotplug->dig_port_work);
> +
> +	spin_unlock_irq(&i915->irq_lock);
>  }
>  
>  /*
> @@ -421,9 +462,10 @@ void intel_hpd_trigger_irq(struct intel_digital_port *dig_port)
>   */
>  static void i915_hotplug_work_func(struct work_struct *work)
>  {
> -	struct drm_i915_private *dev_priv =
> -		container_of(work, struct drm_i915_private,
> -			     display.hotplug.hotplug_work.work);
> +	struct intel_display *display =
> +		container_of(work, struct intel_display, hotplug.hotplug_work.work);
> +	struct drm_i915_private *dev_priv = to_i915(display->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
>  	struct drm_connector_list_iter conn_iter;
>  	struct intel_connector *connector;
>  	u32 changed = 0, retry = 0;
> @@ -431,16 +473,18 @@ static void i915_hotplug_work_func(struct work_struct *work)
>  	u32 hpd_retry_bits;
>  	struct drm_connector *first_changed_connector = NULL;
>  	int changed_connectors = 0;
> +	u32 blocked_hpd_pins;

Same nitpick about naming.

>  
>  	mutex_lock(&dev_priv->drm.mode_config.mutex);
>  	drm_dbg_kms(&dev_priv->drm, "running encoder hotplug functions\n");
>  
>  	spin_lock_irq(&dev_priv->irq_lock);
>  
> -	hpd_event_bits = dev_priv->display.hotplug.event_bits;
> -	dev_priv->display.hotplug.event_bits = 0;
> -	hpd_retry_bits = dev_priv->display.hotplug.retry_bits;
> -	dev_priv->display.hotplug.retry_bits = 0;
> +	blocked_hpd_pins = get_blocked_hpd_pins(display);
> +	hpd_event_bits = hotplug->event_bits & ~blocked_hpd_pins;
> +	hotplug->event_bits &= ~hpd_event_bits;
> +	hpd_retry_bits = hotplug->retry_bits & ~blocked_hpd_pins;
> +	hotplug->retry_bits &= ~hpd_retry_bits;
>  
>  	/* Enable polling for connectors which had HPD IRQ storms */
>  	intel_hpd_irq_storm_switch_to_polling(dev_priv);
> @@ -539,11 +583,13 @@ static void i915_hotplug_work_func(struct work_struct *work)
>  void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
>  			   u32 pin_mask, u32 long_mask)
>  {
> +	struct intel_display *display = to_intel_display(&dev_priv->drm);
>  	struct intel_encoder *encoder;
>  	bool storm_detected = false;
>  	bool queue_dig = false, queue_hp = false;
>  	u32 long_hpd_pulse_mask = 0;
>  	u32 short_hpd_pulse_mask = 0;
> +	u32 blocked_hpd_pins;

Ditto.

>  	enum hpd_pin pin;
>  
>  	if (!pin_mask)
> @@ -551,6 +597,8 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
>  
>  	spin_lock(&dev_priv->irq_lock);
>  
> +	blocked_hpd_pins = get_blocked_hpd_pins(display);
> +
>  	/*
>  	 * Determine whether ->hpd_pulse() exists for each pin, and
>  	 * whether we have a short or a long pulse. This is needed
> @@ -573,7 +621,9 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
>  			"digital hpd on [ENCODER:%d:%s] - %s\n",
>  			encoder->base.base.id, encoder->base.name,
>  			long_hpd ? "long" : "short");
> -		queue_dig = true;
> +
> +		if (!(BIT(pin) & blocked_hpd_pins))

This could also use the hpd_pin_is_blocked() helper.

> +			queue_dig = true;
>  
>  		if (long_hpd) {
>  			long_hpd_pulse_mask |= BIT(pin);
> @@ -617,7 +667,9 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
>  		} else {
>  			dev_priv->display.hotplug.event_bits |= BIT(pin);
>  			long_hpd = true;
> -			queue_hp = true;
> +
> +			if (!(BIT(pin) & blocked_hpd_pins))

Ditto.

> +				queue_hp = true;
>  		}
>  
>  		if (intel_hpd_irq_storm_detect(dev_priv, pin, long_hpd)) {
> @@ -915,11 +967,15 @@ static bool cancel_all_detection_work(struct drm_i915_private *i915)
>  
>  void intel_hpd_cancel_work(struct drm_i915_private *dev_priv)
>  {
> +	struct intel_display *display = to_intel_display(&dev_priv->drm);
> +
>  	if (!HAS_DISPLAY(dev_priv))
>  		return;
>  
>  	spin_lock_irq(&dev_priv->irq_lock);
>  
> +	drm_WARN_ON(display->drm, get_blocked_hpd_pins(display));
> +
>  	dev_priv->display.hotplug.long_hpd_pin_mask = 0;
>  	dev_priv->display.hotplug.short_hpd_pin_mask = 0;
>  	dev_priv->display.hotplug.event_bits = 0;
> @@ -966,19 +1022,22 @@ void intel_hpd_enable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
>  
>  static void queue_work_for_missed_irqs(struct drm_i915_private *i915)
>  {
> -	bool queue_work = false;
> +	struct intel_display *display = to_intel_display(&i915->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
> +	bool queue_hp_work = false;
> +	u32 blocked_hpd_pins;
>  	enum hpd_pin pin;
>  
>  	lockdep_assert_held(&i915->irq_lock);
>  
> -	if (i915->display.hotplug.event_bits ||
> -	    i915->display.hotplug.retry_bits)
> -		queue_work = true;
> +	blocked_hpd_pins = get_blocked_hpd_pins(display);
> +	if ((hotplug->event_bits | hotplug->retry_bits) & ~blocked_hpd_pins)
> +		queue_hp_work = true;
>  
>  	for_each_hpd_pin(pin) {
>  		switch (i915->display.hotplug.stats[pin].state) {
>  		case HPD_MARK_DISABLED:
> -			queue_work = true;
> +			queue_hp_work = true;
>  			break;
>  		case HPD_DISABLED:
>  		case HPD_ENABLED:
> @@ -988,10 +1047,106 @@ static void queue_work_for_missed_irqs(struct drm_i915_private *i915)
>  		}
>  	}
>  
> -	if (queue_work)
> +	if ((hotplug->long_hpd_pin_mask | hotplug->short_hpd_pin_mask) & ~blocked_hpd_pins)
> +		queue_work(hotplug->dp_wq, &hotplug->dig_port_work);
> +
> +	if (queue_hp_work)
>  		queue_delayed_detection_work(i915, &i915->display.hotplug.hotplug_work, 0);
>  }
>  
> +static bool block_hpd_pin(struct intel_display *display, enum hpd_pin pin)
> +{
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
> +
> +	lockdep_assert_held(&i915->irq_lock);
> +
> +	hotplug->stats[pin].blocked_count++;
> +
> +	return hotplug->stats[pin].blocked_count == 1;
> +}
> +
> +static bool unblock_hpd_pin(struct intel_display *display, enum hpd_pin pin)
> +{
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
> +
> +	lockdep_assert_held(&i915->irq_lock);
> +
> +	drm_WARN_ON(display->drm, hotplug->stats[pin].blocked_count == 0);
> +	hotplug->stats[pin].blocked_count--;

Maybe don't change it if it's already 0? I know, shouldn't happen.

> +
> +	return hotplug->stats[pin].blocked_count == 0;
> +}
> +
> +/**
> + * intel_hpd_block - Block handling of HPD IRQs on an HPD pin
> + * @encoder: Encoder to block the HPD handling for
> + *
> + * Blocks the handling of HPD IRQs on the HPD pin of @encoder.
> + *
> + * On return:
> + * - It's guaranteed that the blocked encoders' HPD pulse handler
> + *   (via intel_digital_port::hpd_pulse()) is not running.
> + * - The hotplug event handling (via intel_encoder::hotplug()) of an
> + *   HPD IRQ pending at the time this function is called may be still
> + *   running.
> + * - Detection on the encoder's connector (via
> + *   drm_connector_helper_funcs::detect_ctx(),
> + *   drm_connector_funcs::detect()) remains allowed, for instance as part of
> + *   userspace connector probing, or DRM core's connector polling.
> + *
> + * The call must be followed by calling intel_hpd_unblock().
> + *
> + * Note that the handling of HPD IRQs for another encoder using the same HPD
> + * pin as that of @encoder will be also blocked.
> + */
> +void intel_hpd_block(struct intel_encoder *encoder)
> +{
> +	struct intel_display *display = to_intel_display(encoder);
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +	struct intel_hotplug *hotplug = &display->hotplug;
> +	bool do_flush = false;
> +
> +	if (encoder->hpd_pin == HPD_NONE)
> +		return;
> +
> +	spin_lock_irq(&i915->irq_lock);
> +
> +	if (block_hpd_pin(display, encoder->hpd_pin))
> +		do_flush = true;
> +
> +	spin_unlock_irq(&i915->irq_lock);
> +
> +	if (do_flush && hpd_pin_has_pulse(display, encoder->hpd_pin))
> +		flush_work(&hotplug->dig_port_work);
> +}
> +
> +/**
> + * intel_hpd_unblock - Unblock handling of HPD IRQs on an HPD pin
> + * @encoder: Encoder to unblock the HPD handling for
> + *
> + * Unblock the handling of HPD IRQs on the HPD pin of @encoder, which was
> + * previously blocked by intel_hpd_block(). Any HPD IRQ raised on the
> + * HPD pin while it was blocked will be handled for @encoder and for any
> + * other encoder sharing the same HPD pin.
> + */
> +void intel_hpd_unblock(struct intel_encoder *encoder)
> +{
> +	struct intel_display *display = to_intel_display(encoder);
> +	struct drm_i915_private *i915 = to_i915(display->drm);
> +
> +	if (encoder->hpd_pin == HPD_NONE)
> +		return;
> +
> +	spin_lock_irq(&i915->irq_lock);
> +
> +	if (unblock_hpd_pin(display, encoder->hpd_pin))
> +		queue_work_for_missed_irqs(i915);
> +
> +	spin_unlock_irq(&i915->irq_lock);
> +}
> +
>  void intel_hpd_enable_detection_work(struct drm_i915_private *i915)
>  {
>  	spin_lock_irq(&i915->irq_lock);
> diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.h b/drivers/gpu/drm/i915/display/intel_hotplug.h
> index d6986902b0545..5f9857136f5e3 100644
> --- a/drivers/gpu/drm/i915/display/intel_hotplug.h
> +++ b/drivers/gpu/drm/i915/display/intel_hotplug.h
> @@ -28,6 +28,8 @@ void intel_hpd_cancel_work(struct drm_i915_private *dev_priv);
>  enum hpd_pin intel_hpd_pin_default(enum port port);
>  bool intel_hpd_disable(struct drm_i915_private *dev_priv, enum hpd_pin pin);
>  void intel_hpd_enable(struct drm_i915_private *dev_priv, enum hpd_pin pin);
> +void intel_hpd_block(struct intel_encoder *encoder);
> +void intel_hpd_unblock(struct intel_encoder *encoder);
>  void intel_hpd_debugfs_register(struct drm_i915_private *i915);
>  
>  void intel_hpd_enable_detection_work(struct drm_i915_private *i915);

-- 
Jani Nikula, Intel