Add support for keeping vblank counters sane across mode setting

The DRM supports disabling of vblank interrupts when not in use, but in order
to function properly it must also be aware of mode setting, which will reset
the frame counter to 0.  Add code to call into the DRM before and after mode
setting, so that it can account for any lost vblank events.

1 files changed, 36 insertions, 0 deletions

diff --git a/src/i830_display.c b/src/i830_display.c
index 7857ee36..43a761ce 100644
--- a/src/i830_display.c
+++ b/src/i830_display.c
@@ -35,6 +35,7 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <math.h>
+#include <sys/ioctl.h>
 
 #include "xf86.h"
 #include "i830.h"
@@ -730,6 +731,39 @@ i830_use_fb_compression(xf86CrtcPtr crtc)
     return TRUE;
 }
 
+#if defined(DRM_IOCTL_MODESET_CTL) && defined(XF86DRI)
+static void i830_modeset_ctl(xf86CrtcPtr crtc, int pre)
+{
+    ScrnInfoPtr pScrn = crtc->scrn;
+    I830Ptr pI830 = I830PTR(pScrn);
+    I830CrtcPrivatePtr intel_crtc = crtc->driver_private;
+    struct drm_modeset_ctl modeset;
+
+    modeset.crtc = intel_crtc->plane;
+
+    /*
+     * DPMS will be called many times (especially off), but we only
+     * want to catch the transition from on->off and off->on.
+     */
+    if (pre && intel_crtc->dpms_mode != DPMSModeOff) {
+	/* On -> off is a pre modeset */
+	modeset.cmd = _DRM_PRE_MODESET;
+	ioctl(pI830->drmSubFD, DRM_IOCTL_MODESET_CTL, &modeset);
+	ErrorF("modeset: on -> off on plane %d\n", modeset.crtc);
+    } else if (!pre && intel_crtc->dpms_mode == DPMSModeOff) {
+	/* Off -> on means post modeset */
+	modeset.cmd = _DRM_POST_MODESET;
+	ioctl(pI830->drmSubFD, DRM_IOCTL_MODESET_CTL, &modeset);
+	ErrorF("modeset: off -> on on plane %d\n", modeset.crtc);
+    }
+}
+#else
+static void i830_modeset_ctl(xf86CrtcPtr crtc, int dpms_state)
+{
+    return;
+}
+#endif /* DRM_IOCTL_MODESET_CTL && XF86DRI */
+
 /**
  * Sets the power management mode of the pipe and plane.
  *
@@ -797,8 +831,10 @@ i830_crtc_dpms(xf86CrtcPtr crtc, int mode)
 	/* Reenable compression if needed */
 	if (i830_use_fb_compression(crtc))
 	    i830_enable_fb_compression(crtc);
+	i830_modeset_ctl(crtc, 0);
 	break;
     case DPMSModeOff:
+	i830_modeset_ctl(crtc, 1);
 	/* Shut off compression if in use */
 	if (i830_use_fb_compression(crtc))
 	    i830_disable_fb_compression(crtc);