i965: Rely on hardware contexts for query objects on Gen6+.

Hardware contexts greatly simplify the query object code.  The pipeline
statistics counters get saved and restored with the context, which means
that we don't need to worry about other workloads polluting them.

This means that we can simply write a single pair of values (one at
BeginQuery and one at EndQuery) rather than a series of pairs.  This
also means we don't need to worry about the BO getting full.  We also
don't need to delay BO allocation and starting snapshot until the first
draw.

The generation split here is a little off: technically, Ironlake can also
support hardware contexts.  However, the kernel currently doesn't, and
even if it were to do so someday, we'd need to wait a while before
bumping the kernel requirement to take advantage of it.

v2: Incorporate Paul's feedback.
- Clarify which functions are Gen4/5-only via assertions and comments.
- Change how driver hook initialization happens.
- Update comments.
- Squash a bug fix from a later commit here where it belongs.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net> [v1]
Acked-by: Paul Berry <stereotype441@gmail.com>

1 files changed, 53 insertions, 71 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_queryobj.c b/src/mesa/drivers/dri/i965/brw_queryobj.c
index 40f926b..8579993 100644
--- a/src/mesa/drivers/dri/i965/brw_queryobj.c
+++ b/src/mesa/drivers/dri/i965/brw_queryobj.c
@@ -94,40 +94,23 @@ write_timestamp(struct intel_context *intel, drm_intel_bo *query_bo, int idx)
 static void
 write_depth_count(struct intel_context *intel, drm_intel_bo *query_bo, int idx)
 {
-   if (intel->gen >= 6) {
-      /* Emit Sandybridge workaround flush: */
-      if (intel->gen == 6)
-         intel_emit_post_sync_nonzero_flush(intel);
-
-      BEGIN_BATCH(5);
-      OUT_BATCH(_3DSTATE_PIPE_CONTROL | (5 - 2));
-      OUT_BATCH(PIPE_CONTROL_DEPTH_STALL |
-                PIPE_CONTROL_WRITE_DEPTH_COUNT);
-      OUT_RELOC(query_bo,
-                I915_GEM_DOMAIN_INSTRUCTION, I915_GEM_DOMAIN_INSTRUCTION,
-                PIPE_CONTROL_GLOBAL_GTT_WRITE |
-                (idx * sizeof(uint64_t)));
-      OUT_BATCH(0);
-      OUT_BATCH(0);
-      ADVANCE_BATCH();
-   } else {
-      BEGIN_BATCH(4);
-      OUT_BATCH(_3DSTATE_PIPE_CONTROL | (4 - 2) |
-                PIPE_CONTROL_DEPTH_STALL |
-                PIPE_CONTROL_WRITE_DEPTH_COUNT);
-      /* This object could be mapped cacheable, but we don't have an exposed
-       * mechanism to support that.  Since it's going uncached, tell GEM that
-       * we're writing to it.  The usual clflush should be all that's required
-       * to pick up the results.
-       */
-      OUT_RELOC(query_bo,
-                I915_GEM_DOMAIN_INSTRUCTION, I915_GEM_DOMAIN_INSTRUCTION,
-                PIPE_CONTROL_GLOBAL_GTT_WRITE |
-                (idx * sizeof(uint64_t)));
-      OUT_BATCH(0);
-      OUT_BATCH(0);
-      ADVANCE_BATCH();
-   }
+   assert(intel->gen < 6);
+
+   BEGIN_BATCH(4);
+   OUT_BATCH(_3DSTATE_PIPE_CONTROL | (4 - 2) |
+             PIPE_CONTROL_DEPTH_STALL | PIPE_CONTROL_WRITE_DEPTH_COUNT);
+   /* This object could be mapped cacheable, but we don't have an exposed
+    * mechanism to support that.  Since it's going uncached, tell GEM that
+    * we're writing to it.  The usual clflush should be all that's required
+    * to pick up the results.
+    */
+   OUT_RELOC(query_bo,
+             I915_GEM_DOMAIN_INSTRUCTION, I915_GEM_DOMAIN_INSTRUCTION,
+             PIPE_CONTROL_GLOBAL_GTT_WRITE |
+             (idx * sizeof(uint64_t)));
+   OUT_BATCH(0);
+   OUT_BATCH(0);
+   ADVANCE_BATCH();
 }
 
 /**
@@ -142,6 +125,8 @@ brw_queryobj_get_results(struct gl_context *ctx,
    int i;
    uint64_t *results;
 
+   assert(intel->gen < 6);
+
    if (query->bo == NULL)
       return;
 
@@ -165,36 +150,12 @@ brw_queryobj_get_results(struct gl_context *ctx,
       /* The query BO contains the starting and ending timestamps.
        * Subtract the two and convert to nanoseconds.
        */
-      if (intel->gen >= 6)
-	 query->Base.Result += 80 * (results[1] - results[0]);
-      else
-	 query->Base.Result += 1000 * ((results[1] >> 32) - (results[0] >> 32));
+      query->Base.Result += 1000 * ((results[1] >> 32) - (results[0] >> 32));
       break;
 
    case GL_TIMESTAMP:
       /* The query BO contains a single timestamp value in results[0]. */
-      if (intel->gen >= 6) {
-         /* Our timer is a clock that increments every 80ns (regardless of
-          * other clock scaling in the system).  The timestamp register we can
-          * read for glGetTimestamp() masks out the top 32 bits, so we do that
-          * here too to let the two counters be compared against each other.
-          *
-          * If we just multiplied that 32 bits of data by 80, it would roll
-          * over at a non-power-of-two, so an application couldn't use
-          * GL_QUERY_COUNTER_BITS to handle rollover correctly.  Instead, we
-          * report 36 bits and truncate at that (rolling over 5 times as often
-          * as the HW counter), and when the 32-bit counter rolls over, it
-          * happens to also be at a rollover in the reported value from near
-          * (1<<36) to 0.
-          *
-          * The low 32 bits rolls over in ~343 seconds.  Our 36-bit result
-          * rolls over every ~69 seconds.
-          */
-	 query->Base.Result = 80 * (results[0] & 0xffffffff);
-         query->Base.Result &= (1ull << 36) - 1;
-      } else {
-	 query->Base.Result = 1000 * (results[0] >> 32);
-      }
+      query->Base.Result = 1000 * (results[0] >> 32);
       break;
 
    case GL_SAMPLES_PASSED_ARB:
@@ -280,7 +241,7 @@ brw_delete_query(struct gl_context *ctx, struct gl_query_object *q)
 }
 
 /**
- * Driver hook for glBeginQuery().
+ * Gen4-5 driver hook for glBeginQuery().
  *
  * Initializes driver structures and emits any GPU commands required to begin
  * recording data for the query.
@@ -292,6 +253,8 @@ brw_begin_query(struct gl_context *ctx, struct gl_query_object *q)
    struct intel_context *intel = intel_context(ctx);
    struct brw_query_object *query = (struct brw_query_object *)q;
 
+   assert(intel->gen < 6);
+
    switch (query->Base.Target) {
    case GL_TIME_ELAPSED_EXT:
       /* For timestamp queries, we record the starting time right away so that
@@ -365,7 +328,7 @@ brw_begin_query(struct gl_context *ctx, struct gl_query_object *q)
 }
 
 /**
- * Driver hook for glEndQuery().
+ * Gen4-5 driver hook for glEndQuery().
  *
  * Emits GPU commands to record a final query value, ending any data capturing.
  * However, the final result isn't necessarily available until the GPU processes
@@ -379,6 +342,8 @@ brw_end_query(struct gl_context *ctx, struct gl_query_object *q)
    struct intel_context *intel = intel_context(ctx);
    struct brw_query_object *query = (struct brw_query_object *)q;
 
+   assert(intel->gen < 6);
+
    switch (query->Base.Target) {
    case GL_TIME_ELAPSED_EXT:
       /* Write the final timestamp. */
@@ -450,7 +415,7 @@ brw_end_query(struct gl_context *ctx, struct gl_query_object *q)
 }
 
 /**
- * The WaitQuery() driver hook.
+ * The Gen4-5 WaitQuery() driver hook.
  *
  * Wait for a query result to become available and return it.  This is the
  * backing for glGetQueryObjectiv() with the GL_QUERY_RESULT pname.
@@ -459,12 +424,14 @@ static void brw_wait_query(struct gl_context *ctx, struct gl_query_object *q)
 {
    struct brw_query_object *query = (struct brw_query_object *)q;
 
+   assert(intel_context(ctx)->gen < 6);
+
    brw_queryobj_get_results(ctx, query);
    query->Base.Ready = true;
 }
 
 /**
- * The CheckQuery() driver hook.
+ * The Gen4-5 CheckQuery() driver hook.
  *
  * Checks whether a query result is ready yet.  If not, flushes.
  * This is the backing for glGetQueryObjectiv()'s QUERY_RESULT_AVAILABLE pname.
@@ -474,6 +441,8 @@ static void brw_check_query(struct gl_context *ctx, struct gl_query_object *q)
    struct intel_context *intel = intel_context(ctx);
    struct brw_query_object *query = (struct brw_query_object *)q;
 
+   assert(intel->gen < 6);
+
    /* From the GL_ARB_occlusion_query spec:
     *
     *     "Instead of allowing for an infinite loop, performing a
@@ -501,6 +470,8 @@ ensure_bo_has_space(struct gl_context *ctx, struct brw_query_object *query)
 {
    struct intel_context *intel = intel_context(ctx);
 
+   assert(intel->gen < 6);
+
    if (!query->bo || query->last_index * 2 + 1 >= 4096 / sizeof(uint64_t)) {
 
       if (query->bo != NULL) {
@@ -534,9 +505,7 @@ ensure_bo_has_space(struct gl_context *ctx, struct brw_query_object *query)
  * produces the final expected value.
  *
  * In a world with hardware contexts, PS_DEPTH_COUNT is saved and restored
- * as part of the context state, so this is unnecessary.  We could simply
- * read two values and subtract them.  However, it's safe to continue using
- * the old approach.
+ * as part of the context state, so this is unnecessary, and skipped.
  */
 void
 brw_emit_query_begin(struct brw_context *brw)
@@ -545,6 +514,9 @@ brw_emit_query_begin(struct brw_context *brw)
    struct gl_context *ctx = &intel->ctx;
    struct brw_query_object *query = brw->query.obj;
 
+   if (intel->hw_ctx)
+      return;
+
    /* Skip if we're not doing any queries, or we've already recorded the
     * initial query value for this batchbuffer.
     */
@@ -559,7 +531,8 @@ brw_emit_query_begin(struct brw_context *brw)
 }
 
 /**
- * Called at batchbuffer flush to get an ending PS_DEPTH_COUNT.
+ * Called at batchbuffer flush to get an ending PS_DEPTH_COUNT
+ * (for non-hardware context platforms).
  *
  * See the explanation in brw_emit_query_begin().
  */
@@ -569,6 +542,9 @@ brw_emit_query_end(struct brw_context *brw)
    struct intel_context *intel = &brw->intel;
    struct brw_query_object *query = brw->query.obj;
 
+   if (intel->hw_ctx)
+      return;
+
    if (!brw->query.begin_emitted)
       return;
 
@@ -619,14 +595,20 @@ brw_get_timestamp(struct gl_context *ctx)
    return result;
 }
 
-void brw_init_queryobj_functions(struct dd_function_table *functions)
+/* Initialize query object functions used on all generations. */
+void brw_init_common_queryobj_functions(struct dd_function_table *functions)
 {
    functions->NewQueryObject = brw_new_query_object;
    functions->DeleteQuery = brw_delete_query;
+   functions->QueryCounter = brw_query_counter;
+   functions->GetTimestamp = brw_get_timestamp;
+}
+
+/* Initialize Gen4/5-specific query object functions. */
+void gen4_init_queryobj_functions(struct dd_function_table *functions)
+{
    functions->BeginQuery = brw_begin_query;
    functions->EndQuery = brw_end_query;
-   functions->QueryCounter = brw_query_counter;
    functions->CheckQuery = brw_check_query;
    functions->WaitQuery = brw_wait_query;
-   functions->GetTimestamp = brw_get_timestamp;
 }