drm/i915: CXT_SIZE register offsets added

The GPUs can have different default context layouts, and the sizes could
vary based on platform or BIOS. In order to back the context object with
a properly sized BO, we must read this register in order to find out a
sufficient size.

Thankfully (sarcarm!), the register moves and changes meanings
throughout generations.

CTX and CXT differences are intentional as that is how it is in the
documentation (prior to GEN6 it was CXT).

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

drivers/gpu/drm/i915/i915_reg.h

@@ -1454,6 +1454,27 @@
  */
 #define CCID			0x2180
 #define   CCID_EN		(1<<0)
+#define CXT_SIZE		0x21a0
+#define GEN6_CXT_POWER_SIZE(cxt_reg)	((cxt_reg >> 24) & 0x3f)
+#define GEN6_CXT_RING_SIZE(cxt_reg)	((cxt_reg >> 18) & 0x3f)
+#define GEN6_CXT_RENDER_SIZE(cxt_reg)	((cxt_reg >> 12) & 0x3f)
+#define GEN6_CXT_EXTENDED_SIZE(cxt_reg)	((cxt_reg >> 6) & 0x3f)
+#define GEN6_CXT_PIPELINE_SIZE(cxt_reg)	((cxt_reg >> 0) & 0x3f)
+#define GEN6_CXT_TOTAL_SIZE(cxt_reg)	(GEN6_CXT_POWER_SIZE(cxt_reg) + \
+					GEN6_CXT_RING_SIZE(cxt_reg) + \
+					GEN6_CXT_RENDER_SIZE(cxt_reg) + \
+					GEN6_CXT_EXTENDED_SIZE(cxt_reg) + \
+					GEN6_CXT_PIPELINE_SIZE(cxt_reg))
+#define GEN7_CTX_SIZE		0x21a8
+#define GEN7_CTX_RENDER_SIZE(ctx_reg)	((ctx_reg >> 16) & 0x3f)
+#define GEN7_CTX_EXTENDED_SIZE(ctx_reg)	((ctx_reg >> 9) & 0x7f)
+#define GEN7_CTX_GT1_SIZE(ctx_reg)	((ctx_reg >> 6) & 0x7)
+#define GEN7_CTX_VFSTATE_SIZE(ctx_reg)	((ctx_reg >> 0) & 0x3f)
+#define GEN7_CTX_TOTAL_SIZE(ctx_reg)	(GEN7_CTX_RENDER_SIZE(ctx_reg) + \
+					 GEN7_CTX_EXTENDED_SIZE(ctx_reg) + \
+					 GEN7_CTX_GT1_SIZE(ctx_reg) + \
+					 GEN7_CTX_VFSTATE_SIZE(ctx_reg))
+
 /*
  * Overlay regs
  */