drm/i915: Hold irq uncore.lock when initialising fw_domains

Acquiring the forcewake domain asserts that it is in an atomic section
(as we always expect to be under the uncore.lock). This is true except for
initialising the domains on Ivybridge, and so we generate a warning.
Wrap the manual usage of fw_domains inside the spin_lock.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467566973-13596-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drivers/gpu/drm/i915/intel_uncore.c

@@ -1299,9 +1299,11 @@ static void intel_uncore_fw_domains_init(struct drm_i915_private *dev_priv)
 		fw_domain_init(dev_priv, FW_DOMAIN_ID_RENDER,
 			       FORCEWAKE_MT, FORCEWAKE_MT_ACK);
 
+		spin_lock_irq(&dev_priv->uncore.lock);
 		fw_domains_get_with_thread_status(dev_priv, FORCEWAKE_ALL);
 		ecobus = __raw_i915_read32(dev_priv, ECOBUS);
 		fw_domains_put_with_fifo(dev_priv, FORCEWAKE_ALL);
+		spin_unlock_irq(&dev_priv->uncore.lock);
 
 		if (!(ecobus & FORCEWAKE_MT_ENABLE)) {
 			DRM_INFO("No MT forcewake available on Ivybridge, this can result in issues\n");