queue-6.6/drm-fix-drm_fixp2int_round-making-it-add-0.5.patch

   1 From e3a1169aed4af60c2871cd9cd7ca65719002a597 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Sat, 16 Mar 2024 13:25:20 -0300
   4 Subject: drm: Fix drm_fixp2int_round() making it add 0.5
   5
   6 From: Arthur Grillo <arthurgrillo@riseup.net>
   7
   8 [ Upstream commit 807f96abdf14c80f534c78f2d854c2590963345c ]
   9
  10 As well noted by Pekka[1], the rounding of drm_fixp2int_round is wrong.
  11 To round a number, you need to add 0.5 to the number and floor that,
  12 drm_fixp2int_round() is adding 0.0000076. Make it add 0.5.
  13
  14 [1]: https://lore.kernel.org/all/20240301135327.22efe0dd.pekka.paalanen@collabora.com/
  15
  16 Fixes: 8b25320887d7 ("drm: Add fixed-point helper to get rounded integer values")
  17 Suggested-by: Pekka Paalanen <pekka.paalanen@collabora.com>
  18 Reviewed-by: Harry Wentland <harry.wentland@amd.com>
  19 Reviewed-by: Melissa Wen <mwen@igalia.com>
  20 Signed-off-by: Arthur Grillo <arthurgrillo@riseup.net>
  21 Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
  22 Link: https://patchwork.freedesktop.org/patch/msgid/20240316-drm_fixed-v2-1-c1bc2665b5ed@riseup.net
  23 Signed-off-by: Sasha Levin <sashal@kernel.org>
  24 ---
  25  include/drm/drm_fixed.h | 3 +--
  26  1 file changed, 1 insertion(+), 2 deletions(-)
  27
  28 diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
  29 index 0c9f917a4d4be..81572d32db0c2 100644
  30 --- a/include/drm/drm_fixed.h
  31 +++ b/include/drm/drm_fixed.h
  32 @@ -71,7 +71,6 @@ static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
  33  }
  34
  35  #define DRM_FIXED_POINT                32
  36 -#define DRM_FIXED_POINT_HALF   16
  37  #define DRM_FIXED_ONE          (1ULL << DRM_FIXED_POINT)
  38  #define DRM_FIXED_DECIMAL_MASK (DRM_FIXED_ONE - 1)
  39  #define DRM_FIXED_DIGITS_MASK  (~DRM_FIXED_DECIMAL_MASK)
  40 @@ -90,7 +89,7 @@ static inline int drm_fixp2int(s64 a)
  41
  42  static inline int drm_fixp2int_round(s64 a)
  43  {
  44 -       return drm_fixp2int(a + (1 << (DRM_FIXED_POINT_HALF - 1)));
  45 +       return drm_fixp2int(a + DRM_FIXED_ONE / 2);
  46  }
  47
  48  static inline int drm_fixp2int_ceil(s64 a)
  49 --
  50 2.43.0
  51