drm/i915: move gen6 rps handling to workqueue

The render P-state handling code requires reading from a GT register.
This means that FORCEWAKE must be written to, a resource which is shared
and should be protected by struct_mutex. Hence we can not manipulate
that register from within the interrupt handling and so must delegate
the task to a workqueue.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bafb387..e9d8243 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -682,6 +682,10 @@
 
 	bool mchbar_need_disable;
 
+	struct work_struct rps_work;
+	spinlock_t rps_lock;
+	u32 pm_iir;
+
 	u8 cur_delay;
 	u8 min_delay;
 	u8 max_delay;