[Mesa-dev] [PATCH 1/2] i965: Always try to create a logical context

[Chris Wilson]

Always enable use of HW logical contexts to preserve GPU state between
batches when the kernel supports such constructs, continuing to enforce
the required support for gen6+.

At runtime, this effectively removes the BRW_NEW_CONTEXT flag (and the
upload of invariant state) from the start of every batch for any kernel
supporting contexts. So long as the older atoms are correctly listening
to the right flag (NEW_CONTEXT rather than NEW_BATCH) this should
eliminate a few redundant state uploads for the older platforms.

No piglits were harmed on ctg and ilk, both with and without logical
contexts.

Cc: Jason Ekstrand <jason.ekstrand at intel.com>
Cc: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_context.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 126c187f62..9e0f875b27 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -979,22 +979,21 @@ brwCreateContext(gl_api api,
 
    intel_batchbuffer_init(brw);
 
-   if (devinfo->gen >= 6) {
-      /* Create a new hardware context.  Using a hardware context means that
-       * our GPU state will be saved/restored on context switch, allowing us
-       * to assume that the GPU is in the same state we left it in.
-       *
-       * This is required for transform feedback buffer offsets, query objects,
-       * and also allows us to reduce how much state we have to emit.
-       */
-      brw->hw_ctx = brw_create_hw_context(brw->bufmgr);
-
-      if (!brw->hw_ctx) {
-         fprintf(stderr, "Failed to create hardware context.\n");
-         intelDestroyContext(driContextPriv);
-         return false;
-      }
+   /* Create a new hardware context.  Using a hardware context means that
+    * our GPU state will be saved/restored on context switch, allowing us
+    * to assume that the GPU is in the same state we left it in.
+    *
+    * This is required for transform feedback buffer offsets, query objects,
+    * and also allows us to reduce how much state we have to emit.
+    */
+   brw->hw_ctx = brw_create_hw_context(brw->bufmgr);
+   if (!brw->hw_ctx && devinfo->gen >= 6) {
+      fprintf(stderr, "Failed to create hardware context.\n");
+      intelDestroyContext(driContextPriv);
+      return false;
+   }
 
+   if (brw->hw_ctx) {
       int hw_priority = BRW_CONTEXT_MEDIUM_PRIORITY;
       if (ctx_config->attribute_mask & __DRIVER_CONTEXT_ATTRIB_PRIORITY) {
          switch (ctx_config->priority) {
-- 
2.15.1