drm/i915: Disable MI_STORE_DATA_IMM for i915g/i915gm

The early gen3 machines (i915g/Grantsdale and i915gm/Alviso) share a lot
of characteristics in their MI/GTT blocks with gen2, and in particular
can only use physical addresses in MI_STORE_DATA_IMM. This makes it
incompatible with our usage, so include those two machines in the
blacklist to prevent usage.

v2: Make it easy for gcc and rewrite it as a switch to save some space.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20170906152859.5304-1-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 53718a2..7687483 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1168,6 +1168,9 @@ static u32 *reloc_gpu(struct i915_execbuffer *eb,
 		if (eb_use_cmdparser(eb))
 			return ERR_PTR(-EWOULDBLOCK);
 
+		if (!intel_engine_can_store_dword(eb->engine))
+			return ERR_PTR(-ENODEV);
+
 		err = __reloc_gpu_alloc(eb, vma, len);
 		if (unlikely(err))
 			return ERR_PTR(err);
@@ -1192,9 +1195,7 @@ relocate_entry(struct i915_vma *vma,
 
 	if (!eb->reloc_cache.vaddr &&
 	    (DBG_FORCE_RELOC == FORCE_GPU_RELOC ||
-	     !reservation_object_test_signaled_rcu(vma->resv, true)) &&
-	    __intel_engine_can_store_dword(eb->reloc_cache.gen,
-					   eb->engine->class)) {
+	     !reservation_object_test_signaled_rcu(vma->resv, true))) {
 		const unsigned int gen = eb->reloc_cache.gen;
 		unsigned int len;
 		u32 *batch;