drm/i915: create macros to handle masked bits

... and put them to so good use.

Note that there's functional change in vlv clock gating code, we now
no longer spuriously read back the current value of the bit. According
to Bspec the high bits should always read zero, so ORing this in
should have no effect.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
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 91f1d1c..f1f4d8f 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -29,6 +29,9 @@
 
 #define _PORT(port, a, b) ((a) + (port)*((b)-(a)))
 
+#define _MASKED_BIT_ENABLE(a) (((a) << 16) | (a))
+#define _MASKED_BIT_DISABLE(a) ((a) << 16)
+
 /*
  * The Bridge device's PCI config space has information about the
  * fb aperture size and the amount of pre-reserved memory.
@@ -425,8 +428,6 @@
 #define ARB_MODE		0x04030
 #define   ARB_MODE_SWIZZLE_SNB	(1<<4)
 #define   ARB_MODE_SWIZZLE_IVB	(1<<5)
-#define   ARB_MODE_ENABLE(x)	GFX_MODE_ENABLE(x)
-#define   ARB_MODE_DISABLE(x)	GFX_MODE_DISABLE(x)
 #define RENDER_HWS_PGA_GEN7	(0x04080)
 #define RING_FAULT_REG(ring)	(0x4094 + 0x100*(ring)->id)
 #define DONE_REG		0x40b0
@@ -514,9 +515,6 @@
 #define   GFX_PSMI_GRANULARITY		(1<<10)
 #define   GFX_PPGTT_ENABLE		(1<<9)
 
-#define GFX_MODE_ENABLE(bit) (((bit) << 16) | (bit))
-#define GFX_MODE_DISABLE(bit) (((bit) << 16) | (0))
-
 #define SCPD0		0x0209c /* 915+ only */
 #define IER		0x020a0
 #define IIR		0x020a4