drm/i915/skl: fetch, enable/disable pfit as needed v2

This moved around on SKL, so we need to make sure we read/write the
correct regs.

v2: fixup WIN_POS offsets (Paulo)
    zero out WIN_POS reg at disable time (Paulo)

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuougseek.org>
Signed-off-by: Damien Lespiau <damien.lespiau@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 2bdfe08..afab1dc 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4916,6 +4916,18 @@
 #define PF_VSCALE(pipe)		_PIPE(pipe, _PFA_VSCALE, _PFB_VSCALE)
 #define PF_HSCALE(pipe)		_PIPE(pipe, _PFA_HSCALE, _PFB_HSCALE)
 
+#define _PSA_CTL		0x68180
+#define _PSB_CTL		0x68980
+#define PS_ENABLE		(1<<31)
+#define _PSA_WIN_SZ		0x68174
+#define _PSB_WIN_SZ		0x68974
+#define _PSA_WIN_POS		0x68170
+#define _PSB_WIN_POS		0x68970
+
+#define PS_CTL(pipe)		_PIPE(pipe, _PSA_CTL, _PSB_CTL)
+#define PS_WIN_SZ(pipe)		_PIPE(pipe, _PSA_WIN_SZ, _PSB_WIN_SZ)
+#define PS_WIN_POS(pipe)	_PIPE(pipe, _PSA_WIN_POS, _PSB_WIN_POS)
+
 /* legacy palette */
 #define _LGC_PALETTE_A           0x4a000
 #define _LGC_PALETTE_B           0x4a800