drm/i915/bdw: BDW Software Turbo

BDW supports GT C0 residency reporting in constant time unit. Driver
calculates GT utilization based on C0 residency and adjusts RP
frequency up/down accordingly. For offscreen workload specificly,
set frequency to RP0.

Offscreen task is not restricted by frame rate, it can be
executed as soon as possible. Transcoding and serilized workload
between CPU and GPU both need high GT performance, RP0 is a good
option in this case. RC6 will kick in to compensate power
consumption when GT is not active.

v2: Rebase on recent drm-intel-nightly
v3: Add flip timerout monitor, when no flip is deteced within
100ms, set frequency to RP0.

Signed-off-by: Daisy Sun <daisy.sun@intel.com>
[torourke: rebased on latest and resolved conflict]
Signed-off-by: Tom O'Rourke <Tom.O'Rourke@intel.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 0446114..20673cc 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5562,6 +5562,10 @@
 #define GEN8_UCGCTL6				0x9430
 #define   GEN8_SDEUNIT_CLOCK_GATE_DISABLE	(1<<14)
 
+#define TIMESTAMP_CTR		0x44070
+#define FREQ_1_28_US(us)	(((us) * 100) >> 7)
+#define MCHBAR_PCU_C0		(MCHBAR_MIRROR_BASE_SNB + 0x5960)
+
 #define GEN6_GFXPAUSE				0xA000
 #define GEN6_RPNSWREQ				0xA008
 #define   GEN6_TURBO_DISABLE			(1<<31)