[PATCH 1/2] dri2: Let client call swap before previous swap target has been passed

[Pauli Nieminen]

From: Pauli Nieminen <pauli.nieminen at linux.intel.com>

Client has to be allowed to call swap buffers before last_swap_target
has been passed if driver implements triple buffering with
swap_interval.

Time that swap may come before reaching last_swap_target is swap_limit *
swap_interval if application renders very fast until throttled.

Signed-off-by: Pauli Nieminen <pauli.nieminen at linux.intel.com>
---
 hw/xfree86/dri2/dri2.c |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/hw/xfree86/dri2/dri2.c b/hw/xfree86/dri2/dri2.c
index af3bcae..44a8348 100644
--- a/hw/xfree86/dri2/dri2.c
+++ b/hw/xfree86/dri2/dri2.c
@@ -791,6 +791,14 @@ DRI2WaitSwap(ClientPtr client, DrawablePtr pDrawable)
     return FALSE;
 }
 
+#ifndef WORD64
+# ifdef LONG64
+typedef long INT64;
+# else
+typedef long long INT64;
+#endif
+#endif
+
 int
 DRI2SwapBuffers(ClientPtr client, DrawablePtr pDraw, CARD64 target_msc,
 		CARD64 divisor, CARD64 remainder, CARD64 *swap_target,
@@ -854,12 +862,21 @@ DRI2SwapBuffers(ClientPtr client, DrawablePtr pDraw, CARD64 target_msc,
 	 * got enabled.
 	 */
 	if (ds->GetMSC) {
+	    INT64 msc_diff;
+	    INT64 future_frames_allowed = pPriv->swap_limit * pPriv->swap_interval;
 	    if (!(*ds->GetMSC)(pDraw, &ust, &current_msc))
 		pPriv->last_swap_target = 0;
 
-	    if (current_msc < pPriv->last_swap_target)
-		pPriv->last_swap_target = current_msc;
+	    msc_diff = (INT64)pPriv->last_swap_target - (INT64)current_msc;
 
+	    /*
+	     * If current_msc is more than swap_limit * swap_interval in future
+	     * assume there was CRTC switch. That requires fixing swap_target for
+	     * driver.
+	     */
+	    if (msc_diff < future_frames_allowed)
+		pPriv->last_swap_target = current_msc
+			+ pPriv->swapsPending * pPriv->swap_interval;
 	}
 
 	/*
-- 
1.7.4.1