drm/i915: Only grab correct forcewake for the engine with execlists

Rather than blindly waking up all forcewake domains on command
submission, we can teach each engine what is (or are) the correct
one to take.

On platforms with multiple forcewake domains like VLV, CHV, SKL
and BXT, this has the potential of lowering the GPU and CPU
power use and submission latency.

To implement it we add a function named
intel_uncore_forcewake_for_reg whose purpose is to query which
forcewake domains need to be taken to read or write a specific
register with raw mmio accessors.

These enables the execlists engine setup  to query which
forcewake domains are relevant per engine on the currently
running platform.

v2:
  * Kerneldoc.
  * Split from intel_uncore.c macro extraction, WARN_ON,
    no warns on old platforms. (Chris Wilson)

v3:
  * Single domain per engine, mention all registers,
    bi-directional function and a new name, fix handling
    of gen6 and gen7 writes. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460468251-14069-1-git-send-email-tvrtko.ursulin@linux.intel.com

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 78dc46864a10..2ade194bbea9 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -270,6 +270,7 @@ struct  intel_engine_cs {
 	spinlock_t execlist_lock; /* used inside tasklet, use spin_lock_bh */
 	struct list_head execlist_queue;
 	struct list_head execlist_retired_req_list;
+	unsigned int fw_domains;
 	unsigned int next_context_status_buffer;
 	unsigned int idle_lite_restore_wa;
 	bool disable_lite_restore_wa;