One of the things preventing us from using polling is the fact that
calling valleyview_crt_detect_hotplug() when there's a VGA cable
connected results in sending another hotplug. With polling enabled when
HPD is disabled, this results in a scenario like this:
- We enable power wells and reset the ADPA
- output_poll_exec does force probe on VGA, triggering a hpd
- HPD handler waits for poll to unlock dev->mode_config.mutex
- output_poll_exec shuts off the ADPA, unlocks dev->mode_config.mutex
- HPD handler runs, resets ADPA and brings us back to the start
This results in an endless irq storm getting sent from the ADPA
whenever a VGA connector gets detected in the middle of polling.
Somewhat based off of the "drm/i915: Disable CRT HPD around force
trigger" patch Ville Syrjälä sent a while back
Cc: stable at vger.kernel.org
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Lyude <cpaul at redhat.com>
---
drivers/gpu/drm/i915/i915_drv.h | 2 ++
drivers/gpu/drm/i915/intel_crt.c | 18 ++++++++++++++++++
drivers/gpu/drm/i915/intel_hotplug.c | 27 +++++++++++++++++++++++++++
3 files changed, 47 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a988a95..239a3ec 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2933,6 +2933,8 @@ void intel_hpd_init(struct drm_i915_private *dev_priv);
void intel_hpd_init_work(struct drm_i915_private *dev_priv);
void intel_hpd_cancel_work(struct drm_i915_private *dev_priv);
bool intel_hpd_pin_to_port(enum hpd_pin pin, 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);
/* i915_irq.c */
void i915_queue_hangcheck(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 220be7a..a626793 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -327,10 +327,25 @@ static bool valleyview_crt_detect_hotplug(struct
drm_connector *connector)
struct drm_device *dev = connector->dev;
struct intel_crt *crt = intel_attached_crt(connector);
struct drm_i915_private *dev_priv = dev->dev_private;
+ bool reenable_hpd;
u32 adpa;
bool ret;
u32 save_adpa;
+ /*
+ * Doing a force trigger causes a hpd interrupt to get sent, which can
+ * get us stuck in a loop if we're polling:
+ * - We enable power wells and reset the ADPA
+ * - output_poll_exec does force probe on VGA, triggering a hpd
+ * - HPD handler waits for poll to unlock dev->mode_config.mutex
+ * - output_poll_exec shuts off the ADPA, unlocks
+ * dev->mode_config.mutex
+ * - HPD handler runs, resets ADPA and brings us back to the start
+ *
+ * Just disable HPD interrupts here to prevent this
+ */
+ reenable_hpd = intel_hpd_disable(dev_priv, crt->base.hpd_pin);
+
save_adpa = adpa = I915_READ(crt->adpa_reg);
DRM_DEBUG_KMS("trigger hotplug detect cycle: adpa=0x%x\n", adpa);
@@ -353,6 +368,9 @@ static bool valleyview_crt_detect_hotplug(struct
drm_connector *connector)
DRM_DEBUG_KMS("valleyview hotplug adpa=0x%x, result %d\n", adpa, ret);
+ if (reenable_hpd)
+ intel_hpd_enable(dev_priv, crt->base.hpd_pin);
+
return ret;
}
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c
b/drivers/gpu/drm/i915/intel_hotplug.c
index 38eeca7..ec3285f 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -510,3 +510,30 @@ void intel_hpd_cancel_work(struct drm_i915_private
*dev_priv)
cancel_work_sync(&dev_priv->hotplug.hotplug_work);
cancel_delayed_work_sync(&dev_priv->hotplug.reenable_work);
}
+
+bool intel_hpd_disable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
+{
+ bool ret = false;
+
+ if (pin == HPD_NONE)
+ return false;
+
+ spin_lock_irq(&dev_priv->irq_lock);
+ if (dev_priv->hotplug.stats[pin].state == HPD_ENABLED) {
+ dev_priv->hotplug.stats[pin].state = HPD_DISABLED;
+ ret = true;
+ }
+ spin_unlock_irq(&dev_priv->irq_lock);
+
+ return ret;
+}
+
+void intel_hpd_enable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
+{
+ if (pin == HPD_NONE)
+ return;
+
+ spin_lock_irq(&dev_priv->irq_lock);
+ dev_priv->hotplug.stats[pin].state = HPD_ENABLED;
+ spin_unlock_irq(&dev_priv->irq_lock);
+}
--
2.5.5
