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>

1 files changed, 7 insertions, 7 deletions

diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
index f5e1168c7647..d639049a613d 100644
--- a/include/drm/drm_fixed.h
+++ b/include/drm/drm_fixed.h
@@ -84,12 +84,12 @@ static inline int drm_fixp2int(int64_t a)
         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 @@ static inline s64 drm_fixp_mul(s64 a, s64 b)
         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_mul(s64 a, s64 b)
 
 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 @@ static inline s64 drm_fixp_exp(s64 x)
         }
 
         if (x < 0)
-                sum = drm_fixp_div(1, sum);
+                sum = drm_fixp_div(DRM_FIXED_ONE, sum);
 
         return sum;
 }