drm/i915: Return a default RCS context size

Instead of returning whatever size the latest GEN used. This is because
context sizes for new GENs can go up or down, but the only safe thing to
do for missing cases is to use the largest known one, whatever that is.

Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1515711307-28979-1-git-send-email-oscar.mateo@intel.com
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index b221610..3639af5 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -38,6 +38,7 @@
  */
 #define HSW_CXT_TOTAL_SIZE		(17 * PAGE_SIZE)
 
+#define DEFAULT_LR_CONTEXT_RENDER_SIZE	(22 * PAGE_SIZE)
 #define GEN8_LR_CONTEXT_RENDER_SIZE	(20 * PAGE_SIZE)
 #define GEN9_LR_CONTEXT_RENDER_SIZE	(22 * PAGE_SIZE)
 #define GEN10_LR_CONTEXT_RENDER_SIZE	(18 * PAGE_SIZE)
@@ -157,6 +158,7 @@
 		switch (INTEL_GEN(dev_priv)) {
 		default:
 			MISSING_CASE(INTEL_GEN(dev_priv));
+			return DEFAULT_LR_CONTEXT_RENDER_SIZE;
 		case 10:
 			return GEN10_LR_CONTEXT_RENDER_SIZE;
 		case 9: