This patch disables hotplug interrupts if an 'interrupt storm'
has been detected.
Noise on the interrupt line renders the hotplug interrupt useless:
each hotplug event causes the devices to be rescanned which will
will only increase the system load.
Thus disable the hotplug interrupts and fall back to periodic
device polling.

v2: Fixed cleanup typo.

Signed-off-by: Egbert Eich <e...@suse.de>
---
 drivers/gpu/drm/i915/i915_irq.c |   69 ++++++++++++++++++++++++++++++---------
 1 files changed, 53 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index d9c99d7..0abef6a 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -87,7 +87,8 @@ static const u32 hpd_status_i915[] = { /* i915 and valleyview 
are the same */
        [HPD_PORT_D] = PORTD_HOTPLUG_INT_STATUS
 };
 
-
+static void ibx_hpd_irq_setup(struct drm_device *dev);
+static void i915_hpd_irq_setup(struct drm_device *dev);
 
 /* For display hotplug interrupt */
 static void
@@ -338,7 +339,11 @@ static void i915_hotplug_work_func(struct work_struct 
*work)
                                                    hotplug_work);
        struct drm_device *dev = dev_priv->dev;
        struct drm_mode_config *mode_config = &dev->mode_config;
-       struct intel_encoder *encoder;
+       struct intel_connector *intel_connector;
+       struct intel_encoder *intel_encoder;
+       struct drm_connector *connector;
+       unsigned long irqflags;
+       bool connector_disabled = false;
 
        /* HPD irq before everything is fully set up. */
        if (!dev_priv->enable_hotplug_processing)
@@ -347,9 +352,29 @@ static void i915_hotplug_work_func(struct work_struct 
*work)
        mutex_lock(&mode_config->mutex);
        DRM_DEBUG_KMS("running encoder hotplug functions\n");
 
-       list_for_each_entry(encoder, &mode_config->encoder_list, base.head)
-               if (encoder->hot_plug)
-                       encoder->hot_plug(encoder);
+       spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+       list_for_each_entry(connector, &mode_config->connector_list, head) {
+               intel_connector = to_intel_connector(connector);
+               intel_encoder = intel_connector->encoder;
+               if (intel_encoder->hpd_pin > HPD_NONE &&
+                   dev_priv->hpd_stats[intel_encoder->hpd_pin].hpd_mark == 
HPD_MARK_DISABLED &&
+                   connector->polled == DRM_CONNECTOR_POLL_HPD) {
+                       pr_warn("HPD interrupt storm detected on connector %s 
disabling\n",
+                               drm_get_connector_name(connector));
+                       dev_priv->hpd_stats[intel_encoder->hpd_pin].hpd_mark = 
HPD_DISABLED;
+                       connector->polled = DRM_CONNECTOR_POLL_CONNECT
+                               | DRM_CONNECTOR_POLL_DISCONNECT;
+                       connector_disabled = true;
+               }
+       }
+       if (connector_disabled)
+               drm_kms_helper_poll_enable(dev); /* if there were no outputs to 
poll, poll is disabled */
+
+       spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
+
+       list_for_each_entry(intel_encoder, &mode_config->encoder_list, 
base.head)
+               if (intel_encoder->hot_plug)
+                       intel_encoder->hot_plug(intel_encoder);
 
        mutex_unlock(&mode_config->mutex);
 
@@ -578,13 +603,14 @@ static void gen6_queue_rps_work(struct drm_i915_private 
*dev_priv,
        queue_work(dev_priv->wq, &dev_priv->rps.work);
 }
 
-static inline void hotplug_irq_storm_detect(struct drm_device *dev,
+static inline bool hotplug_irq_storm_detect(struct drm_device *dev,
                                            u32 hotplug_trigger,
                                            const u32 *hpd)
 {
        drm_i915_private_t *dev_priv = dev->dev_private;
        unsigned long irqflags;
        int i;
+       bool ret = false;
 
        spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
 
@@ -598,12 +624,15 @@ static inline void hotplug_irq_storm_detect(struct 
drm_device *dev,
                        } else if (dev_priv->hpd_stats[i].hpd_cnt > 5) {
                                dev_priv->hpd_stats[i].hpd_mark = 
HPD_MARK_DISABLED;
                                DRM_DEBUG_KMS("HPD interrupt storm detected on  
PIN %d\n", i);
+                               ret = true;
                        } else
                                dev_priv->hpd_stats[i].hpd_cnt++;
                }
        }
 
        spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
+
+       return ret;
 }
 
 static void gmbus_irq_handler(struct drm_device *dev)
@@ -679,7 +708,8 @@ static irqreturn_t valleyview_irq_handler(int irq, void 
*arg)
                        DRM_DEBUG_DRIVER("hotplug event received, stat 
0x%08x\n",
                                         hotplug_status);
                        if (hotplug_trigger) {
-                               hotplug_irq_storm_detect(dev, hotplug_trigger, 
hpd_status_i915);
+                               if( hotplug_irq_storm_detect(dev, 
hotplug_trigger, hpd_status_i915))
+                                       i915_hpd_irq_setup(dev);
                                queue_work(dev_priv->wq,
                                           &dev_priv->hotplug_work);
                        }
@@ -709,7 +739,8 @@ static void ibx_irq_handler(struct drm_device *dev, u32 
pch_iir)
        u32 hotplug_trigger = pch_iir & SDE_HOTPLUG_MASK;
 
        if (hotplug_trigger) {
-               hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_ibx);
+               if (hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_ibx))
+                       ibx_hpd_irq_setup(dev);
                queue_work(dev_priv->wq, &dev_priv->hotplug_work);
        }
        if (pch_iir & SDE_AUDIO_POWER_MASK)
@@ -757,7 +788,8 @@ static void cpt_irq_handler(struct drm_device *dev, u32 
pch_iir)
        u32 hotplug_trigger = pch_iir & SDE_HOTPLUG_MASK_CPT;
 
        if (hotplug_trigger) {
-               hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_cpt);
+               if (hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_cpt))
+                       ibx_hpd_irq_setup(dev);
                queue_work(dev_priv->wq, &dev_priv->hotplug_work);
        }
        if (pch_iir & SDE_AUDIO_POWER_MASK_CPT)
@@ -2034,12 +2066,14 @@ static void ibx_hpd_irq_setup(struct drm_device *dev)
        if (HAS_PCH_IBX(dev)) {
                mask &= ~SDE_HOTPLUG_MASK;
                list_for_each_entry(intel_encoder, &mode_config->encoder_list, 
base.head)
-                       mask |= hpd_ibx[intel_encoder->hpd_pin];
+                       if 
(dev_priv->hpd_stats[intel_encoder->hpd_pin].hpd_mark == HPD_ENABLED)
+                               mask |= hpd_ibx[intel_encoder->hpd_pin];
                mask |= SDE_GMBUS | SDE_AUX_MASK;
        } else {
                mask &= ~SDE_HOTPLUG_MASK_CPT;
                list_for_each_entry(intel_encoder, &mode_config->encoder_list, 
base.head)
-                       mask |= hpd_cpt[intel_encoder->hpd_pin];
+                       if 
(dev_priv->hpd_stats[intel_encoder->hpd_pin].hpd_mark == HPD_ENABLED)
+                               mask |= hpd_cpt[intel_encoder->hpd_pin];
                mask |= SDE_GMBUS_CPT | SDE_AUX_MASK_CPT;
        }
        I915_WRITE(SDEIIR, I915_READ(SDEIIR));
@@ -2505,7 +2539,8 @@ static irqreturn_t i915_irq_handler(int irq, void *arg)
                        DRM_DEBUG_DRIVER("hotplug event received, stat 
0x%08x\n",
                                  hotplug_status);
                        if (hotplug_trigger) {
-                               hotplug_irq_storm_detect(dev, hotplug_trigger, 
hpd_status_i915);
+                               if (hotplug_irq_storm_detect(dev, 
hotplug_trigger, hpd_status_i915))
+                                       i915_hpd_irq_setup(dev);
                                queue_work(dev_priv->wq,
                                           &dev_priv->hotplug_work);
                        }
@@ -2659,7 +2694,7 @@ static void i915_hpd_irq_setup(struct drm_device *dev)
 {
        drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
        struct drm_mode_config *mode_config = &dev->mode_config;
-       struct intel_encoder *encoder;
+       struct intel_encoder *intel_encoder;
        u32 hotplug_en;
 
        if (I915_HAS_HOTPLUG(dev)) {
@@ -2668,7 +2703,8 @@ static void i915_hpd_irq_setup(struct drm_device *dev)
                /* Note HDMI and DP share hotplug bits */
                /* enable bits are the same for all generations */
                list_for_each_entry(intel_encoder, &mode_config->encoder_list, 
base.head)
-                       hotplug_en |= hpd_mask_i915[intel_encoder->hpd_pin];
+                       if 
(dev_priv->hpd_stats[intel_encoder->hpd_pin].hpd_mark == HPD_ENABLED)
+                               hotplug_en |= 
hpd_mask_i915[intel_encoder->hpd_pin];
                /* Programming the CRT detection parameters tends
                   to generate a spurious hotplug event about three
                   seconds later.  So just do it once.
@@ -2742,8 +2778,9 @@ static irqreturn_t i965_irq_handler(int irq, void *arg)
                        DRM_DEBUG_DRIVER("hotplug event received, stat 
0x%08x\n",
                                  hotplug_status);
                        if (hotplug_trigger) {
-                               hotplug_irq_storm_detect(dev, hotplug_trigger,
-                                                        IS_G4X(dev) ? 
hpd_status_gen4 : hpd_status_i965);
+                               if (hotplug_irq_storm_detect(dev, 
hotplug_trigger,
+                                                           IS_G4X(dev) ? 
hpd_status_gen4 : hpd_status_i965))
+                                       i915_hpd_irq_setup(dev);
                                queue_work(dev_priv->wq,
                                           &dev_priv->hotplug_work);
                        }
-- 
1.7.7

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