Mesa (intel-2008-q4): dri: Fix driWaitForMSC32 when divisor >= 2 and msc < 0.

[Haihao Xiang]

Module: Mesa
Branch: intel-2008-q4
Commit: 37f489edd217f7a92998b7ca9207d43e2860b357
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=37f489edd217f7a92998b7ca9207d43e2860b357

Author: Eric Anholt <eric at anholt.net>
Date:   Tue Dec 23 16:08:40 2008 -0800

dri: Fix driWaitForMSC32 when divisor >= 2 and msc < 0.

We'd come up with a negative remainder, while we were looking for the positive
version of it in the loop conditional.  And, since the "did we hit our target"
break was disabled for the target_msc == 0 ("Just make the divisor/remainder
work") path, we'd never exit.

Simplify the code by just using int64_t all over instead of trying to do it
in a u32 space.
(cherry picked from commit 6c01500228014a6cfa133b5dbba8c6d024833e84)

---

 src/mesa/drivers/dri/common/vblank.c |   18 +++++++++---------
 1 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/mesa/drivers/dri/common/vblank.c b/src/mesa/drivers/dri/common/vblank.c
index d610253..12aeaa1 100644
--- a/src/mesa/drivers/dri/common/vblank.c
+++ b/src/mesa/drivers/dri/common/vblank.c
@@ -130,9 +130,8 @@ int driWaitForMSC32( __DRIdrawablePrivate *priv,
 
 
    if ( divisor != 0 ) {
-      unsigned int target = (unsigned int)target_msc;
-      unsigned int next = target;
-      unsigned int r;
+      int64_t next = target_msc;
+      int64_t r;
       int dont_wait = (target_msc == 0);
 
       do {
@@ -154,9 +153,9 @@ int driWaitForMSC32( __DRIdrawablePrivate *priv,
 
 	 *msc = vblank_to_msc(priv, vbl.reply.sequence);
 
-         dont_wait = 0;
-         if (target_msc != 0 && *msc == target)
+         if (!dont_wait && *msc == next)
             break;
+         dont_wait = 0;
 
          /* Assuming the wait-done test fails, the next refresh to wait for
           * will be one that satisfies (MSC % divisor) == remainder.  The
@@ -165,11 +164,12 @@ int driWaitForMSC32( __DRIdrawablePrivate *priv,
           * If this refresh has already happened, we add divisor to obtain 
           * the next refresh after the current one that will satisfy it.
           */
-         r = (*msc % (unsigned int)divisor);
-         next = (*msc - r + (unsigned int)remainder);
-         if (next <= *msc) next += (unsigned int)divisor;
+         r = ((uint64_t)*msc % divisor);
+         next = (*msc - r + remainder);
+         if (next <= *msc)
+	    next += divisor;
 
-      } while ( r != (unsigned int)remainder );
+      } while (r != remainder);
    }
    else {
       /* If the \c divisor is zero, just wait until the MSC is greater