msm: kgsl: convert timestamp_cmp logic to use unsigned logic
msm: kgsl: convert timestamp_cmp logic to use unsigned logic
The meaning of timestamps becomes difficult to understand when
converting between unsigned and signed values. Values that
were seperated by 0x80000000 also returned inconsistent
results.
CRs-Fixed: 355752
Conflicts:
drivers/gpu/msm/kgsl.h
Change-Id: I5d5d1ad64ef120da8769d72ac69dde37f8f5c6ae
Signed-off-by: Jeff Boody <jboody@codeaurora.org>
diff --git a/drivers/gpu/msm/kgsl.h b/drivers/gpu/msm/kgsl.h
index fd592c7..c3635b8 100644
--- a/drivers/gpu/msm/kgsl.h
+++ b/drivers/gpu/msm/kgsl.h
@@ -25,7 +25,7 @@
#define KGSL_NAME "kgsl"
-/* Timestamp window used to detect rollovers */
+/* Timestamp window used to detect rollovers (half of integer range) */
#define KGSL_TIMESTAMP_WINDOW 0x80000000
/*cache coherency ops */
@@ -206,14 +206,24 @@
return memdesc->hostptr + (gpuaddr - memdesc->gpuaddr);
}
-static inline int timestamp_cmp(unsigned int new, unsigned int old)
+static inline int timestamp_cmp(unsigned int a, unsigned int b)
{
- int ts_diff = new - old;
-
- if (ts_diff == 0)
+ /* check for equal */
+ if (a == b)
return 0;
- return ((ts_diff > 0) || (ts_diff < -KGSL_TIMESTAMP_WINDOW)) ? 1 : -1;
+ /* check for greater-than for non-rollover case */
+ if ((a > b) && (a - b < KGSL_TIMESTAMP_WINDOW))
+ return 1;
+
+ /* check for greater-than for rollover case
+ * note that <= is required to ensure that consistent
+ * results are returned for values whose difference is
+ * equal to the window size
+ */
+ a += KGSL_TIMESTAMP_WINDOW;
+ b += KGSL_TIMESTAMP_WINDOW;
+ return ((a > b) && (a - b <= KGSL_TIMESTAMP_WINDOW)) ? 1 : -1;
}
static inline void