drm/i915/debugfs: Add i915_hpd_storm_ctl

This adds a file in i915's debugfs directory that allows userspace to
manually control HPD storm detection. This is mainly for hotplugging
tests, where we might want to test HPD storm functionality or disable
storm detection to speed up hotplugging tests without breaking anything.

Changes since v1:
- Make HPD storm interval configurable
- Misc code cleanup

Signed-off-by: Lyude <lyude@redhat.com>
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Tomeu Vizoso <tomeu@tomeuvizoso.net>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index b62e3f8ad415..6a9c16508ab5 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -100,7 +100,6 @@ bool intel_hpd_pin_to_port(enum hpd_pin pin, enum port *port)
 }
 
 #define HPD_STORM_DETECT_PERIOD		1000
-#define HPD_STORM_THRESHOLD		5
 #define HPD_STORM_REENABLE_DELAY	(2 * 60 * 1000)
 
 /**
@@ -112,9 +111,13 @@ bool intel_hpd_pin_to_port(enum hpd_pin pin, enum port *port)
  * storms. Only the pin specific stats and state are changed, the caller is
  * responsible for further action.
  *
- * @HPD_STORM_THRESHOLD irqs are allowed within @HPD_STORM_DETECT_PERIOD ms,
- * otherwise it's considered an irq storm, and the irq state is set to
- * @HPD_MARK_DISABLED.
+ * The number of irqs that are allowed within @HPD_STORM_DETECT_PERIOD is
+ * stored in @dev_priv->hotplug.hpd_storm_threshold which defaults to
+ * @HPD_STORM_DEFAULT_THRESHOLD. If this threshold is exceeded, it's
+ * considered an irq storm and the irq state is set to @HPD_MARK_DISABLED.
+ *
+ * The HPD threshold can be controlled through i915_hpd_storm_ctl in debugfs,
+ * and should only be adjusted for automated hotplug testing.
  *
  * Return true if an irq storm was detected on @pin.
  */
@@ -123,13 +126,15 @@ static bool intel_hpd_irq_storm_detect(struct drm_i915_private *dev_priv,
 {
 	unsigned long start = dev_priv->hotplug.stats[pin].last_jiffies;
 	unsigned long end = start + msecs_to_jiffies(HPD_STORM_DETECT_PERIOD);
+	const int threshold = dev_priv->hotplug.hpd_storm_threshold;
 	bool storm = false;
 
 	if (!time_in_range(jiffies, start, end)) {
 		dev_priv->hotplug.stats[pin].last_jiffies = jiffies;
 		dev_priv->hotplug.stats[pin].count = 0;
 		DRM_DEBUG_KMS("Received HPD interrupt on PIN %d - cnt: 0\n", pin);
-	} else if (dev_priv->hotplug.stats[pin].count > HPD_STORM_THRESHOLD) {
+	} else if (dev_priv->hotplug.stats[pin].count > threshold &&
+		   threshold) {
 		dev_priv->hotplug.stats[pin].state = HPD_MARK_DISABLED;
 		DRM_DEBUG_KMS("HPD interrupt storm detected on PIN %d\n", pin);
 		storm = true;