drm/i915: Reset the interrupt mask on disabling interrupts

As we disable the interrupt during suspend, also reset the irq_mask to
short-circuit subsystems that later try to turn off their interrupt
source.

<4>[  101.816730] i915 0000:00:02.0: drm_WARN_ON(!intel_irqs_enabled(dev_priv))
<4>[  101.816853] WARNING: CPU: 3 PID: 4241 at drivers/gpu/drm/i915/i915_irq.c:343 ilk_update_display_irq+0xb3/0x130 [i915]

v2: Reset irq_mask for i8xx_irq_reset as well, and split patch to focus
on only i915->irq_mask
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201022114246.28566-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_irq.c

@@ -337,17 +337,14 @@ void ilk_update_display_irq(struct drm_i915_private *dev_priv,
 	u32 new_val;
 
 	lockdep_assert_held(&dev_priv->irq_lock);
-
 	drm_WARN_ON(&dev_priv->drm, enabled_irq_mask & ~interrupt_mask);
 
-	if (drm_WARN_ON(&dev_priv->drm, !intel_irqs_enabled(dev_priv)))
-		return;
-
 	new_val = dev_priv->irq_mask;
 	new_val &= ~interrupt_mask;
 	new_val |= (~enabled_irq_mask & interrupt_mask);
 
-	if (new_val != dev_priv->irq_mask) {
+	if (new_val != dev_priv->irq_mask &&
+	    !drm_WARN_ON(&dev_priv->drm, !intel_irqs_enabled(dev_priv))) {
 		dev_priv->irq_mask = new_val;
 		I915_WRITE(DEIMR, dev_priv->irq_mask);
 		POSTING_READ(DEIMR);
@@ -2951,6 +2948,8 @@ static void ilk_irq_reset(struct drm_i915_private *dev_priv)
 	struct intel_uncore *uncore = &dev_priv->uncore;
 
 	GEN3_IRQ_RESET(uncore, DE);
+	dev_priv->irq_mask = ~0u;
+
 	if (IS_GEN(dev_priv, 7))
 		intel_uncore_write(uncore, GEN7_ERR_INT, 0xffffffff);
 
@@ -3695,6 +3694,7 @@ static void i8xx_irq_reset(struct drm_i915_private *dev_priv)
 	i9xx_pipestat_irq_reset(dev_priv);
 
 	GEN2_IRQ_RESET(uncore);
+	dev_priv->irq_mask = ~0u;
 }
 
 static void i8xx_irq_postinstall(struct drm_i915_private *dev_priv)
@@ -3864,6 +3864,7 @@ static void i915_irq_reset(struct drm_i915_private *dev_priv)
 	i9xx_pipestat_irq_reset(dev_priv);
 
 	GEN3_IRQ_RESET(uncore, GEN2_);
+	dev_priv->irq_mask = ~0u;
 }
 
 static void i915_irq_postinstall(struct drm_i915_private *dev_priv)
@@ -3970,6 +3971,7 @@ static void i965_irq_reset(struct drm_i915_private *dev_priv)
 	i9xx_pipestat_irq_reset(dev_priv);
 
 	GEN3_IRQ_RESET(uncore, GEN2_);
+	dev_priv->irq_mask = ~0u;
 }
 
 static void i965_irq_postinstall(struct drm_i915_private *dev_priv)