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drm: Add drm_fixp_from_fraction and drm_fixp2int_ceil

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drm_fixp_from_fraction allows us to create a fixed point directly
from a fraction, rather than creating fixed point values and dividing
later. This avoids overflow of our 64 bit value for large numbers.

drm_fixp2int_ceil allows us to return the ceiling of our fixed point
value.

[airlied: squash Jordan's fix]
32-bit-build-fix: Jordan Lazare <Jordan.Lazare@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Harry Wentland 2016-01-22 17:07:25 -05:00 committed by Dave Airlie
parent 4d6a10da79
commit 64566b5e76
1 changed files with 51 additions and 2 deletions
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53
include/drm/drm_fixed.h
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@ -73,18 +73,28 @@ static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
#define DRM_FIXED_ONE (1ULL << DRM_FIXED_POINT)
#define DRM_FIXED_DECIMAL_MASK (DRM_FIXED_ONE - 1)
#define DRM_FIXED_DIGITS_MASK (~DRM_FIXED_DECIMAL_MASK)
#define DRM_FIXED_EPSILON 1LL
#define DRM_FIXED_ALMOST_ONE (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
static inline s64 drm_int2fixp(int a)
{
return ((s64)a) << DRM_FIXED_POINT;
}
static inline int drm_fixp2int(int64_t a)
static inline int drm_fixp2int(s64 a)
{
return ((s64)a) >> DRM_FIXED_POINT;
}
static inline unsigned drm_fixp_msbset(int64_t a)
static inline int drm_fixp2int_ceil(s64 a)
{
if (a > 0)
return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
else
return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
}
static inline unsigned drm_fixp_msbset(s64 a)
{
unsigned shift, sign = (a >> 63) & 1;
@ -136,6 +146,45 @@ static inline s64 drm_fixp_div(s64 a, s64 b)
return result;
}
static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
{
s64 res;
bool a_neg = a < 0;
bool b_neg = b < 0;
u64 a_abs = a_neg ? -a : a;
u64 b_abs = b_neg ? -b : b;
u64 rem;
/* determine integer part */
u64 res_abs = div64_u64_rem(a_abs, b_abs, &rem);
/* determine fractional part */
{
u32 i = DRM_FIXED_POINT;
do {
rem <<= 1;
res_abs <<= 1;
if (rem >= b_abs) {
res_abs |= 1;
rem -= b_abs;
}
} while (--i != 0);
}
/* round up LSB */
{
u64 summand = (rem << 1) >= b_abs;
res_abs += summand;
}
res = (s64) res_abs;
if (a_neg ^ b_neg)
res = -res;
return res;
}
static inline s64 drm_fixp_exp(s64 x)
{
s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);