[2/3] i915: Add support for out-of-bound hotplug events

[Hans de Goede <hdegoede@redhat.com>]

On some Cherry Trail devices, DisplayPort over Type-C is supported through
a USB-PD microcontroller (e.g. a fusb302) + a mux to switch the superspeed
datalines between USB-3 and DP (e.g. a pi3usb30532). The kernel in this
case does the PD/alt-mode negotiation itself, rather then everything being
handled in firmware.

So the kernel itself picks an alt-mode, tells the Type-C "dongle" to switch
to DP mode and sets the mux accordingly. In this setup the HPD pin is not
connected, so the i915 driver needs to respond to a software event and scan
the DP port for changes manually.

This commit adds support for this. Together with the recent addition of
DP alt-mode support to the Type-C subsystem this makes DP over Type-C
work on these devices.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/gpu/drm/i915/i915_drv.h      |  2 ++
 drivers/gpu/drm/i915/i915_irq.c      |  2 ++
 drivers/gpu/drm/i915/intel_hotplug.c | 38 ++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b1c31967194b..5d8c585ddbf7 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -153,6 +153,7 @@ enum hpd_pin {
 
 struct i915_hotplug {
 	struct work_struct hotplug_work;
+	struct notifier_block oob_notifier;
 
 	struct {
 		unsigned long last_jiffies;
@@ -2632,6 +2633,7 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
 			   u32 pin_mask, u32 long_mask);
 void intel_hpd_init(struct drm_i915_private *dev_priv);
 void intel_hpd_init_work(struct drm_i915_private *dev_priv);
+void intel_hpd_fini_work(struct drm_i915_private *dev_priv);
 void intel_hpd_cancel_work(struct drm_i915_private *dev_priv);
 enum hpd_pin intel_hpd_pin_default(struct drm_i915_private *dev_priv,
 				   enum port port);
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 8211045a981b..14f3323b721b 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -4965,6 +4965,8 @@ void intel_irq_fini(struct drm_i915_private *i915)
 
 	for (i = 0; i < MAX_L3_SLICES; ++i)
 		kfree(i915->l3_parity.remap_info[i]);
+
+	intel_hpd_fini_work(i915);
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index e24174d08fed..221878fa26af 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -518,6 +518,36 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
 		schedule_work(&dev_priv->hotplug.hotplug_work);
 }
 
+static int intel_hpd_oob_notifier(struct notifier_block *nb,
+				  unsigned long event, void *data)
+{
+	struct drm_i915_private *dev_priv =
+		container_of(nb, struct drm_i915_private, hotplug.oob_notifier);
+	struct intel_encoder *encoder;
+	u32 bits = 0;
+
+	/* We only support DP over Type-C notifications */
+	if (event != DRM_OOB_HOTPLUG_TYPE_C_DP)
+		return NOTIFY_DONE;
+
+	/* Schedule a hotplug check for each DP encoder, except for EDP ones */
+	for_each_intel_dp(&dev_priv->drm, encoder) {
+		if (encoder->type == INTEL_OUTPUT_EDP)
+			continue;
+
+		bits |= BIT(encoder->hpd_pin);
+	}
+
+	if (bits) {
+		spin_lock_irq(&dev_priv->irq_lock);
+		dev_priv->hotplug.event_bits |= bits;
+		spin_unlock_irq(&dev_priv->irq_lock);
+		schedule_work(&dev_priv->hotplug.hotplug_work);
+	}
+
+	return NOTIFY_DONE;
+}
+
 /**
  * intel_hpd_init - initializes and enables hpd support
  * @dev_priv: i915 device instance
@@ -640,6 +670,14 @@ void intel_hpd_init_work(struct drm_i915_private *dev_priv)
 	INIT_WORK(&dev_priv->hotplug.poll_init_work, i915_hpd_poll_init_work);
 	INIT_DELAYED_WORK(&dev_priv->hotplug.reenable_work,
 			  intel_hpd_irq_storm_reenable_work);
+	dev_priv->hotplug.oob_notifier.notifier_call = intel_hpd_oob_notifier;
+	drm_kms_register_oob_hotplug_notifier(&dev_priv->hotplug.oob_notifier);
+}
+
+void intel_hpd_fini_work(struct drm_i915_private *dev_priv)
+{
+	drm_kms_unregister_oob_hotplug_notifier(
+					&dev_priv->hotplug.oob_notifier);
 }
 
 void intel_hpd_cancel_work(struct drm_i915_private *dev_priv)