drm: fix 64 bit drm fixed point helpers
Sign bit wasn't handled properly and a small typo.
Thanks to Christian for helping me sort this out.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
index f5e1168..d639049 100644
--- a/include/drm/drm_fixed.h
+++ b/include/drm/drm_fixed.h
@@ -84,12 +84,12 @@
return ((s64)a) >> DRM_FIXED_POINT;
}
-static inline s64 drm_fixp_msbset(int64_t a)
+static inline unsigned drm_fixp_msbset(int64_t a)
{
unsigned shift, sign = (a >> 63) & 1;
for (shift = 62; shift > 0; --shift)
- if ((a >> shift) != sign)
+ if (((a >> shift) & 1) != sign)
return shift;
return 0;
@@ -100,9 +100,9 @@
unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
s64 result;
- if (shift > 63) {
- shift = shift - 63;
- a >>= shift >> 1;
+ if (shift > 61) {
+ shift = shift - 61;
+ a >>= (shift >> 1) + (shift & 1);
b >>= shift >> 1;
} else
shift = 0;
@@ -120,7 +120,7 @@
static inline s64 drm_fixp_div(s64 a, s64 b)
{
- unsigned shift = 63 - drm_fixp_msbset(a);
+ unsigned shift = 62 - drm_fixp_msbset(a);
s64 result;
a <<= shift;
@@ -154,7 +154,7 @@
}
if (x < 0)
- sum = drm_fixp_div(1, sum);
+ sum = drm_fixp_div(DRM_FIXED_ONE, sum);
return sum;
}