[cogl/fosdem-2012: 11/16] egl-kms: Use drmModePageFlip

[Robert Bragg <rbragg src gnome org>]

commit 9558cfdee56807f56c751994d1e8ad6effc8a422
Author: Neil Roberts <neil linux intel com>
Date:   Mon Dec 19 17:17:28 2011 +0000

    egl-kms: Use drmModePageFlip
    
    The KMS platform now uses drmModePageFlip to present the buffer. The
    main loop mechanism is used to poll for events on the DRM file
    descriptor so that we notice when the page flip is complete. The
    swap_buffers is throttled so that if there is a pending flip it will
    block until it is complete before starting another flip.

 cogl/winsys/cogl-winsys-egl-kms.c |  126 ++++++++++++++++++++++++++++++++-----
 1 files changed, 110 insertions(+), 16 deletions(-)
---
diff --git a/cogl/winsys/cogl-winsys-egl-kms.c b/cogl/winsys/cogl-winsys-egl-kms.c
index f92b2a1..5122484 100644
--- a/cogl/winsys/cogl-winsys-egl-kms.c
+++ b/cogl/winsys/cogl-winsys-egl-kms.c
@@ -35,11 +35,13 @@
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
 #include <drm.h>
+#include <xf86drm.h>
 #include <xf86drmMode.h>
 #include <gbm.h>
 #include <glib.h>
 #include <sys/fcntl.h>
 #include <unistd.h>
+#include <string.h>
 
 #include "cogl-winsys-egl-kms-private.h"
 #include "cogl-winsys-egl-private.h"
@@ -55,6 +57,7 @@ typedef struct _CoglRendererKMS
 {
   int fd;
   struct gbm_device *gbm;
+  CoglPollFD poll_fd;
 } CoglRendererKMS;
 
 typedef struct _CoglDisplayKMS
@@ -134,6 +137,9 @@ _cogl_winsys_renderer_connect (CoglRenderer *renderer,
   if (!_cogl_winsys_egl_renderer_connect_common (renderer, error))
     goto egl_terminate;
 
+  kms_renderer->poll_fd.fd = kms_renderer->fd;
+  kms_renderer->poll_fd.events = COGL_POLL_FD_EVENT_IN;
+
   return TRUE;
 
 egl_terminate:
@@ -301,6 +307,52 @@ _cogl_winsys_egl_cleanup_context (CoglDisplay *display)
 }
 
 static void
+page_flip_handler (int fd,
+                   unsigned int frame,
+                   unsigned int sec,
+                   unsigned int usec,
+                   void *data)
+{
+  CoglOnscreen *onscreen = data;
+  CoglOnscreenEGL *egl_onscreen = onscreen->winsys;
+  CoglOnscreenKMS *kms_onscreen = egl_onscreen->platform;
+  CoglContext *context = COGL_FRAMEBUFFER (onscreen)->context;
+  CoglRenderer *renderer = context->display->renderer;
+  CoglRendererEGL *egl_renderer = renderer->winsys;
+  CoglRendererKMS *kms_renderer = egl_renderer->platform;
+
+  if (kms_onscreen->current_fb_id)
+    {
+      drmModeRmFB (kms_renderer->fd,
+                   kms_onscreen->current_fb_id);
+      kms_onscreen->current_fb_id = 0;
+    }
+  if (kms_onscreen->current_bo)
+    {
+      gbm_surface_release_bo (kms_onscreen->surface,
+                              kms_onscreen->current_bo);
+      kms_onscreen->current_bo = NULL;
+    }
+
+  kms_onscreen->current_fb_id = kms_onscreen->next_fb_id;
+  kms_onscreen->next_fb_id = 0;
+
+  kms_onscreen->current_bo = kms_onscreen->next_bo;
+  kms_onscreen->next_bo = NULL;
+}
+
+static void
+handle_drm_event (CoglRendererKMS *kms_renderer)
+{
+  drmEventContext evctx;
+
+  memset (&evctx, 0, sizeof evctx);
+  evctx.version = DRM_EVENT_CONTEXT_VERSION;
+  evctx.page_flip_handler = page_flip_handler;
+  drmHandleEvent (kms_renderer->fd, &evctx);
+}
+
+static void
 _cogl_winsys_onscreen_swap_buffers (CoglOnscreen *onscreen)
 {
   CoglContext *context = COGL_FRAMEBUFFER (onscreen)->context;
@@ -311,18 +363,20 @@ _cogl_winsys_onscreen_swap_buffers (CoglOnscreen *onscreen)
   CoglRendererKMS *kms_renderer = egl_renderer->platform;
   CoglOnscreenEGL *egl_onscreen = onscreen->winsys;
   CoglOnscreenKMS *kms_onscreen = egl_onscreen->platform;
-  struct gbm_bo *next_bo;
   EGLint handle, pitch;
-  uint32_t next_fb_id;
+
+  /* If we already have a pending swap then block until it completes */
+  while (kms_onscreen->next_fb_id != 0)
+    handle_drm_event (kms_renderer);
 
   /* First chain-up. This will call eglSwapBuffers */
   parent_vtable->onscreen_swap_buffers (onscreen);
 
   /* Now we need to set the CRTC to whatever is the front buffer */
-  next_bo = gbm_surface_get_bo (kms_onscreen->surface);
+  kms_onscreen->next_bo = gbm_surface_get_bo (kms_onscreen->surface);
 
-  pitch = gbm_bo_get_pitch (next_bo);
-  handle = gbm_bo_get_handle (next_bo).u32;
+  pitch = gbm_bo_get_pitch (kms_onscreen->next_bo);
+  handle = gbm_bo_get_handle (kms_onscreen->next_bo).u32;
 
   if (drmModeAddFB (kms_renderer->fd,
                     kms_display->width,
@@ -331,19 +385,21 @@ _cogl_winsys_onscreen_swap_buffers (CoglOnscreen *onscreen)
                     32, /* bpp */
                     pitch,
                     handle,
-                    &next_fb_id) == 0)
+                    &kms_onscreen->next_fb_id) == 0)
     {
-      if (drmModeSetCrtc (kms_renderer->fd,
-                          kms_display->encoder->crtc_id,
-                          next_fb_id,
-                          0, 0, /* x, y */
-                          &kms_display->connector->connector_id,
-                          1, /* count */
-                          &kms_display->mode) != 0)
-        g_error (G_STRLOC ": Setting CRTC failed");
+      drmModePageFlip (kms_renderer->fd,
+                       kms_display->encoder->crtc_id,
+                       kms_onscreen->next_fb_id,
+                       DRM_MODE_PAGE_FLIP_EVENT,
+                       onscreen);
+    }
+  else
+    {
+      gbm_surface_release_bo (kms_onscreen->surface,
+                              kms_onscreen->next_bo);
+      kms_onscreen->next_bo = NULL;
+      kms_onscreen->next_fb_id = 0;
     }
-
-  gbm_surface_release_bo (kms_onscreen->surface, next_bo);
 }
 
 static gboolean
@@ -435,6 +491,41 @@ _cogl_winsys_onscreen_deinit (CoglOnscreen *onscreen)
   onscreen->winsys = NULL;
 }
 
+static void
+_cogl_winsys_context_begin_idle (CoglContext *context,
+                                 CoglPollFD **poll_fds,
+                                 int *n_poll_fds,
+                                 gint64 *timeout)
+{
+  CoglRenderer *renderer = context->display->renderer;
+  CoglRendererEGL *egl_renderer = renderer->winsys;
+  CoglRendererKMS *kms_renderer = egl_renderer->platform;
+
+  *poll_fds = &kms_renderer->poll_fd;
+  *n_poll_fds = 1;
+  *timeout = -1;
+}
+
+static void
+_cogl_winsys_context_dispatch (CoglContext *context,
+                               const CoglPollFD *poll_fds,
+                               int n_poll_fds)
+{
+  CoglRenderer *renderer = context->display->renderer;
+  CoglRendererEGL *egl_renderer = renderer->winsys;
+  CoglRendererKMS *kms_renderer = egl_renderer->platform;
+  int i;
+
+  for (i = 0; i < n_poll_fds; i++)
+    if (poll_fds[i].fd == kms_renderer->fd)
+      {
+        if (poll_fds[i].revents)
+          handle_drm_event (kms_renderer);
+
+        break;
+      }
+}
+
 static const CoglWinsysEGLVtable
 _cogl_winsys_egl_vtable =
   {
@@ -471,6 +562,9 @@ _cogl_winsys_egl_kms_get_vtable (void)
       vtable.onscreen_swap_region = NULL;
       vtable.onscreen_swap_buffers = _cogl_winsys_onscreen_swap_buffers;
 
+      vtable.context_begin_idle = _cogl_winsys_context_begin_idle;
+      vtable.context_dispatch = _cogl_winsys_context_dispatch;
+
       vtable_inited = TRUE;
     }