drm/i915: Support variable cursor height on ivb+

IVB introduced the CUR_FBC_CTL register which allows reducing the cursor
height down to 8 lines from the otherwise square cursor dimensions.
Implement support for it. CUR_FBC_CTL can't be used when the cursor
is rotated.

Commandeer the otherwise unused cursor->cursor.size to track the
current value of CUR_FBC_CTL to optimize away redundant CUR_FBC_CTL
writes, and to notice when we need to arm the update via CURBASE if
just CUR_FBC_CTL changes.

v2: Reverse the gen check to make it sane
v3: Only enable CUR_FBC_CTL when cursor is enabled, adapt to
    earlier code changes which means we now actually turn off
    the cursor when we're supposed to unlike v2
v4: Add a comment about rotation vs. CUR_FBC_CTL,
    rebase due to 'dirty' (Chris)
v5: Rebase to the atomic world
    Handle 180 degree rotation
    Add HAS_CUR_FBC()
v6: Rebase
v7: Rebase due to I915_WRITE_FW/uncore.lock
    s/size/fbc_ctl/

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170327185546.2977-12-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 2b151dc..ee144ec 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5449,7 +5449,9 @@ enum {
 #define   CURSOR_POS_SIGN       0x8000
 #define   CURSOR_X_SHIFT        0
 #define   CURSOR_Y_SHIFT        16
-#define CURSIZE			_MMIO(0x700a0)
+#define CURSIZE			_MMIO(0x700a0) /* 845/865 */
+#define _CUR_FBC_CTL_A		0x700a0 /* ivb+ */
+#define   CUR_FBC_CTL_EN	(1 << 31)
 #define _CURBCNTR		0x700c0
 #define _CURBBASE		0x700c4
 #define _CURBPOS		0x700c8
@@ -5465,6 +5467,7 @@ enum {
 #define CURCNTR(pipe) _CURSOR2(pipe, _CURACNTR)
 #define CURBASE(pipe) _CURSOR2(pipe, _CURABASE)
 #define CURPOS(pipe) _CURSOR2(pipe, _CURAPOS)
+#define CUR_FBC_CTL(pipe) _CURSOR2(pipe, _CUR_FBC_CTL_A)
 
 #define CURSOR_A_OFFSET 0x70080
 #define CURSOR_B_OFFSET 0x700c0