[PATCH] drm/i915/debugfs: Add i915_hpd_storm_ctl

[Lyude]

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.

Signed-off-by: Lyude <lyude@xxxxxxxxxx>
Cc: Tomeu Vizoso <tomeu@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_debugfs.c  | 102 ++++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/i915_drv.h      |   2 +
 drivers/gpu/drm/i915/i915_irq.c      |   2 +
 drivers/gpu/drm/i915/intel_hotplug.c |   3 +-
 4 files changed, 107 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 3ae0656..b985c7b 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -4624,6 +4624,105 @@ static int i915_forcewake_create(struct dentry *root, struct drm_minor *minor)
 	return drm_add_fake_info_node(minor, ent, &i915_forcewake_fops);
 }
 
+static int i915_hpd_storm_ctl_show(struct seq_file *m, void *data)
+{
+	struct drm_i915_private *dev_priv = m->private;
+
+	if (delayed_work_pending(&dev_priv->hotplug.reenable_work))
+		seq_printf(m, "detected\n");
+	else if (dev_priv->hotplug.hpd_storm_detect_enabled)
+		seq_printf(m, "on\n");
+	else
+		seq_printf(m, "off\n");
+
+	return 0;
+}
+
+static void i915_hpd_storm_reset(struct drm_i915_private *dev_priv)
+{
+	int i;
+
+	spin_lock_irq(&dev_priv->irq_lock);
+	for (i = 0; i < ARRAY_SIZE(dev_priv->hotplug.stats); i++) {
+		dev_priv->hotplug.stats[i].count = 0;
+		dev_priv->hotplug.stats[i].last_jiffies = jiffies;
+	}
+	spin_unlock_irq(&dev_priv->irq_lock);
+
+	if (delayed_work_pending(&dev_priv->hotplug.reenable_work))
+		flush_delayed_work(&dev_priv->hotplug.reenable_work);
+	else
+		schedule_delayed_work(&dev_priv->hotplug.reenable_work, 0);
+}
+
+static ssize_t i915_hpd_storm_ctl_write(struct file *file,
+					const char __user *ubuf, size_t len,
+					loff_t *offp)
+{
+	struct seq_file *m = file->private_data;
+	struct drm_i915_private *dev_priv = m->private;
+	struct i915_hotplug *hotplug = &dev_priv->hotplug;
+	char tmp[16];
+	enum {
+		HPD_STORM_DISABLE = 0,
+		HPD_STORM_ENABLE,
+		HPD_STORM_RESET
+	} action;
+
+	if (len >= sizeof(tmp))
+		return -EINVAL;
+
+	if (copy_from_user(tmp, ubuf, len))
+		return -EFAULT;
+
+	tmp[len] = '\0';
+
+	if (strcmp(tmp, "off") == 0 || strcmp(tmp, "off\n") == 0)
+		action = HPD_STORM_DISABLE;
+	else if (strcmp(tmp, "on") == 0 || strcmp(tmp, "on\n") == 0)
+		action = HPD_STORM_ENABLE;
+	else if (strcmp(tmp, "reset") == 0 || strcmp(tmp, "reset\n") == 0)
+		action = HPD_STORM_RESET;
+	else
+		return -EINVAL;
+
+	switch (action) {
+		case HPD_STORM_DISABLE:
+			DRM_DEBUG_KMS("Disabling HPD storm detection\n");
+
+			WRITE_ONCE(hotplug->hpd_storm_detect_enabled, false);
+			i915_hpd_storm_reset(dev_priv);
+			break;
+		case HPD_STORM_ENABLE:
+			DRM_DEBUG_KMS("Enabling HPD storm detection\n");
+
+			i915_hpd_storm_reset(dev_priv);
+			hotplug->hpd_storm_detect_enabled = true;
+			break;
+		case HPD_STORM_RESET:
+			DRM_DEBUG_KMS("Resetting HPD storm stats\n");
+
+			i915_hpd_storm_reset(dev_priv);
+			break;
+	}
+
+	return len;
+}
+
+static int i915_hpd_storm_ctl_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, i915_hpd_storm_ctl_show, inode->i_private);
+}
+
+static const struct file_operations i915_hpd_storm_ctl_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_hpd_storm_ctl_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+	.write = i915_hpd_storm_ctl_write
+};
+
 static int i915_debugfs_create(struct dentry *root,
 			       struct drm_minor *minor,
 			       const char *name,
@@ -4717,7 +4816,8 @@ static const struct i915_debugfs_files {
 	{"i915_dp_test_data", &i915_displayport_test_data_fops},
 	{"i915_dp_test_type", &i915_displayport_test_type_fops},
 	{"i915_dp_test_active", &i915_displayport_test_active_fops},
-	{"i915_guc_log_control", &i915_guc_log_control_fops}
+	{"i915_guc_log_control", &i915_guc_log_control_fops},
+	{"i915_hpd_storm_ctl", &i915_hpd_storm_ctl_fops}
 };
 
 int i915_debugfs_register(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bd5a38b..b11596f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -407,6 +407,8 @@ struct i915_hotplug {
 	struct work_struct poll_init_work;
 	bool poll_enabled;
 
+	bool hpd_storm_detect_enabled;
+
 	/*
 	 * if we get a HPD irq from DP and a HPD irq from non-DP
 	 * the non-DP HPD could block the workqueue on a mode config
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 059d66b..ed3292d 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -4225,6 +4225,8 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 	if (!IS_GEN2(dev_priv))
 		dev->vblank_disable_immediate = true;
 
+	dev_priv->hotplug.hpd_storm_detect_enabled = true;
+
 	dev->driver->get_vblank_timestamp = i915_get_vblank_timestamp;
 	dev->driver->get_scanout_position = i915_get_crtc_scanoutpos;
 
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index b62e3f8..c1e37dd 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -129,7 +129,8 @@ static bool intel_hpd_irq_storm_detect(struct drm_i915_private *dev_priv,
 		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 > HPD_STORM_THRESHOLD &&
+		   dev_priv->hotplug.hpd_storm_detect_enabled) {
 		dev_priv->hotplug.stats[pin].state = HPD_MARK_DISABLED;
 		DRM_DEBUG_KMS("HPD interrupt storm detected on PIN %d\n", pin);
 		storm = true;
-- 
2.9.3