[Intel-gfx] [PATCH 2/4] drm/i915: Fix hotplug irq ack on i965/g4x

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Just like with PIPESTAT, the edge triggered IIR on i965/g4x
also causes problems for hotplug interrupts. To make sure
we don't get the IIR port interrupt bit stuck low with the
ISR bit high we must force an edge in ISR. We do that by
clearing PORT_HOTPLUG_EN temporaryly when we ack
PORT_HOTPLUG_STAT.

Cc: stable at vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 364e1c85315e..59250ecbd0d9 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1998,10 +1998,35 @@ static void valleyview_pipestat_irq_handler(struct drm_i915_private *dev_priv,
 
 static u32 i9xx_hpd_irq_ack(struct drm_i915_private *dev_priv)
 {
-	u32 hotplug_status = I915_READ(PORT_HOTPLUG_STAT);
+	u32 hotplug_status, hotplug_en;
 
-	if (hotplug_status)
-		I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status);
+	hotplug_status = I915_READ(PORT_HOTPLUG_STAT);
+
+	if (IS_G4X(dev_priv) ||
+	    IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
+		hotplug_status &= HOTPLUG_INT_STATUS_G4X |
+			DP_AUX_CHANNEL_MASK_INT_STATUS_G4X;
+	else
+		hotplug_status &= HOTPLUG_INT_STATUS_I915;
+
+	if (hotplug_status == 0)
+		return 0;
+
+	spin_lock(&dev_priv->irq_lock);
+
+	/*
+	 * Toggle all PORT_HOTPLUG_EN bits to make sure we
+	 * get an edge in the ISR port interrupt bit if we
+	 * don't clear all the enabled status bits. Otherwise
+	 * the edge triggered IIR on i965/g4x wouldn't notice
+	 * that an interrupt is still pending.
+	 */
+	hotplug_en = I915_READ(PORT_HOTPLUG_EN);
+	I915_WRITE(PORT_HOTPLUG_EN, 0);
+	I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status);
+	I915_WRITE(PORT_HOTPLUG_EN, hotplug_en);
+
+	spin_unlock(&dev_priv->irq_lock);
 
 	return hotplug_status;
 }
-- 
2.16.4