drm/i915: gen6_enable_rps() wants to be called after ring initialisation

Currently we call gen6_enable_rps() (which writes into the per-ring
register mmio space) from intel_modeset_init_hw() which is called before
we initialise the rings. If we defer intel_modeset_init_hw() until
afterwards (in the intel_modeset_gem_init() phase) all is well.

v2: Rectify ordering of gem vs display HW init upon resume. (Daniel)

v3: Fix up locking. (Paulo)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Smash Paulo's locking fix onto Chris' patch.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_suspend.c

@@ -876,12 +876,6 @@ int i915_restore_state(struct drm_device *dev)
 		I915_WRITE(IER, dev_priv->saveIER);
 		I915_WRITE(IMR, dev_priv->saveIMR);
 	}
-	mutex_unlock(&dev->struct_mutex);
-
-	if (drm_core_check_feature(dev, DRIVER_MODESET))
-		intel_modeset_init_hw(dev);
-
-	mutex_lock(&dev->struct_mutex);
 
 	/* Cache mode state */
 	I915_WRITE(CACHE_MODE_0, dev_priv->saveCACHE_MODE_0 | 0xffff0000);