st/egl: Implement swapbuffer throttling

When doing copy swapbuffers using drm, throttle on outstanding copy operations.
Introduces a new environment variable, EGL_THROTTLE_FENCES that the
user can use to indicate the desired number of outstanding swapbuffers, or
disable throttling using EGL_THROTTLE_FENCES=0.

This can and perhaps should be extended to the pageflip case as well, since
with some hardware pageflips can be pipelined. In case the pageflip syncs, the
throttle operation will be a no-op anyway.

Update copyright notices.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>

1 files changed, 102 insertions, 1 deletions

diff --git a/src/gallium/state_trackers/egl/common/native_helper.c b/src/gallium/state_trackers/egl/common/native_helper.c
index 0f00c4d13e..be6713d03a 100644
--- a/src/gallium/state_trackers/egl/common/native_helper.c
+++ b/src/gallium/state_trackers/egl/common/native_helper.c
@@ -3,6 +3,7 @@
  * Version:  7.9
  *
  * Copyright (C) 2010 LunarG Inc.
+ * Copyright (C) 2011 VMware Inc. All rights reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -24,6 +25,7 @@
  *
  * Authors:
  *    Chia-I Wu <olv@lunarg.com>
+ *    Thomas Hellstrom <thellstrom@vmware.com>
  */
 
 #include "util/u_inlines.h"
@@ -34,6 +36,14 @@
 
 #include "native_helper.h"
 
+/**
+ * Number of swap fences and mask
+ */
+
+#define EGL_SWAP_FENCES_MAX 4
+#define EGL_SWAP_FENCES_MASK 3
+#define EGL_SWAP_FENCES_DEFAULT 1
+
 struct resource_surface {
    struct pipe_screen *screen;
    enum pipe_format format;
@@ -42,6 +52,15 @@ struct resource_surface {
    struct pipe_resource *resources[NUM_NATIVE_ATTACHMENTS];
    uint resource_mask;
    uint width, height;
+
+   /**
+    * Swap fences.
+    */
+   struct pipe_fence_handle *swap_fences[EGL_SWAP_FENCES_MAX];
+   unsigned int cur_fences;
+   unsigned int head;
+   unsigned int tail;
+   unsigned int desired_fences;
 };
 
 struct resource_surface *
@@ -49,11 +68,16 @@ resource_surface_create(struct pipe_screen *screen,
                         enum pipe_format format, uint bind)
 {
    struct resource_surface *rsurf = CALLOC_STRUCT(resource_surface);
+   char *swap_fences = getenv("EGL_THROTTLE_FENCES");
 
    if (rsurf) {
       rsurf->screen = screen;
       rsurf->format = format;
       rsurf->bind = bind;
+      rsurf->desired_fences = (swap_fences) ? atoi(swap_fences) :
+	 EGL_SWAP_FENCES_DEFAULT;
+      if (rsurf->desired_fences > EGL_SWAP_FENCES_MAX)
+	 rsurf->desired_fences = EGL_SWAP_FENCES_MAX;
    }
 
    return rsurf;
@@ -256,7 +280,6 @@ resource_surface_copy_swap(struct resource_surface *rsurf,
    u_box_origin_2d(ftex->width0, ftex->height0, &src_box);
    pipe->resource_copy_region(pipe, ftex, 0, 0, 0, 0,
 			      btex, 0, &src_box);
-   pipe->flush(pipe, PIPE_FLUSH_RENDER_CACHE, NULL);
    ret = TRUE;
 
  out_no_ftex:
@@ -266,3 +289,81 @@ resource_surface_copy_swap(struct resource_surface *rsurf,
 
    return ret;
 }
+
+static struct pipe_fence_handle *
+swap_fences_pop_front(struct resource_surface *rsurf)
+{
+   struct pipe_screen *screen = rsurf->screen;
+   struct pipe_fence_handle *fence = NULL;
+
+   if (rsurf->desired_fences == 0)
+      return NULL;
+
+   if (rsurf->cur_fences >= rsurf->desired_fences) {
+      screen->fence_reference(screen, &fence, rsurf->swap_fences[rsurf->tail]);
+      screen->fence_reference(screen, &rsurf->swap_fences[rsurf->tail++], NULL);
+      rsurf->tail &= EGL_SWAP_FENCES_MASK;
+      --rsurf->cur_fences;
+   }
+   return fence;
+}
+
+static void
+swap_fences_push_back(struct resource_surface *rsurf,
+		      struct pipe_fence_handle *fence)
+{
+   struct pipe_screen *screen = rsurf->screen;
+
+   if (!fence || rsurf->desired_fences == 0)
+      return;
+
+   while(rsurf->cur_fences == rsurf->desired_fences)
+      swap_fences_pop_front(rsurf);
+
+   rsurf->cur_fences++;
+   screen->fence_reference(screen, &rsurf->swap_fences[rsurf->head++],
+			   fence);
+   rsurf->head &= EGL_SWAP_FENCES_MASK;
+}
+
+boolean
+resource_surface_throttle(struct resource_surface *rsurf)
+{
+   struct pipe_screen *screen = rsurf->screen;
+   struct pipe_fence_handle *fence = swap_fences_pop_front(rsurf);
+
+   if (fence) {
+      (void) screen->fence_finish(screen, fence, 0);
+      screen->fence_reference(screen, &fence, NULL);
+      return TRUE;
+   }
+
+   return FALSE;
+}
+
+boolean
+resource_surface_flush(struct resource_surface *rsurf,
+		       struct native_display *ndpy)
+{
+   struct pipe_fence_handle *fence = NULL;
+   struct pipe_screen *screen = rsurf->screen;
+   struct pipe_context *pipe= ndpy_get_copy_context(ndpy);
+
+   if (!pipe)
+      return FALSE;
+
+   pipe->flush(pipe, PIPE_FLUSH_RENDER_CACHE, &fence);
+   if (fence == NULL)
+      return FALSE;
+
+   swap_fences_push_back(rsurf, fence);
+   screen->fence_reference(screen, &fence, NULL);
+
+   return TRUE;
+}
+
+void
+resource_surface_wait(struct resource_surface *rsurf)
+{
+   while (resource_surface_throttle(rsurf));
+}