drm/i915/psr: Always wait for idle state when disabling PSR

It should always wait for idle state when disabling PSR because PSR
could be inactive due a call to intel_psr_exit() and while PSR is
still being disabled asynchronously userspace could change the
modeset causing a call to psr_disable() that will not wait for PSR
idle and then PSR will be enabled again while PSR is still not idle.

v2: rebased on top of the patch reusing psr_exit()

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181106190843.18009-2-jose.souza@intel.com

drivers/gpu/drm/i915/intel_psr.c

@@ -661,8 +661,12 @@ static void intel_psr_exit(struct drm_i915_private *dev_priv)
 {
 	u32 val;
 
-	if (!dev_priv->psr.active)
+	if (!dev_priv->psr.active) {
+		if (INTEL_GEN(dev_priv) >= 9)
+			WARN_ON(I915_READ(EDP_PSR2_CTL) & EDP_PSR2_ENABLE);
+		WARN_ON(I915_READ(EDP_PSR_CTL) & EDP_PSR_ENABLE);
 		return;
+	}
 
 	if (dev_priv->psr.psr2_enabled) {
 		val = I915_READ(EDP_PSR2_CTL);
@@ -680,8 +684,6 @@ static void
 intel_psr_disable_source(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
-
-	if (dev_priv->psr.active) {
 	i915_reg_t psr_status;
 	u32 psr_status_mask;
 
@@ -696,16 +698,9 @@ intel_psr_disable_source(struct intel_dp *intel_dp)
 	}
 
 	/* Wait till PSR is idle */
-		if (intel_wait_for_register(dev_priv,
-					    psr_status, psr_status_mask, 0,
+	if (intel_wait_for_register(dev_priv, psr_status, psr_status_mask, 0,
 				    2000))
-			DRM_ERROR("Timed out waiting for PSR Idle State\n");
-	} else {
-		if (dev_priv->psr.psr2_enabled)
-			WARN_ON(I915_READ(EDP_PSR2_CTL) & EDP_PSR2_ENABLE);
-		else
-			WARN_ON(I915_READ(EDP_PSR_CTL) & EDP_PSR_ENABLE);
-	}
+		DRM_ERROR("Timed out waiting PSR idle state\n");
 }
 
 static void intel_psr_disable_locked(struct intel_dp *intel_dp)