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drm: add some additional fixed point helpers (v3) 

Required for certain driver calculations.  Code
was written by Christian König and ported to the
drm by me.

v2: fix 64 bit divides
v3: fix 64 bit for real (math64.h)

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Alex Deucher 2013-03-22 10:35:50 -04:00
parent 9ed36f7505
commit 210a0b9e21
1 changed files with 94 additions and 0 deletions
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94
include/drm/drm_fixed.h
View File

@ -20,10 +20,13 @@
* OTHER DEALINGS IN THE SOFTWARE.
*
* Authors: Dave Airlie
* Christian König
*/
#ifndef DRM_FIXED_H
#define DRM_FIXED_H
#include <linux/math64.h>
typedef union dfixed {
u32 full;
} fixed20_12;
@ -65,4 +68,95 @@ static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
tmp /= 2;
return lower_32_bits(tmp);
}
#define DRM_FIXED_POINT 32
#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)
static inline s64 drm_int2fixp(int a)
{
return ((s64)a) << DRM_FIXED_POINT;
}
static inline int drm_fixp2int(int64_t a)
{
return ((s64)a) >> DRM_FIXED_POINT;
}
static inline s64 drm_fixp_msbset(int64_t a)
{
unsigned shift, sign = (a >> 63) & 1;
for (shift = 62; shift > 0; --shift)
if ((a >> shift) != sign)
return shift;
return 0;
}
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;
b >>= shift >> 1;
} else
shift = 0;
result = a * b;
if (shift > DRM_FIXED_POINT)
return result << (shift - DRM_FIXED_POINT);
if (shift < DRM_FIXED_POINT)
return result >> (DRM_FIXED_POINT - shift);
return result;
}
static inline s64 drm_fixp_div(s64 a, s64 b)
{
unsigned shift = 63 - drm_fixp_msbset(a);
s64 result;
a <<= shift;
if (shift < DRM_FIXED_POINT)
b >>= (DRM_FIXED_POINT - shift);
result = div64_s64(a, b);
if (shift > DRM_FIXED_POINT)
return result >> (shift - DRM_FIXED_POINT);
return result;
}
static inline s64 drm_fixp_exp(s64 x)
{
s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
s64 sum = DRM_FIXED_ONE, term, y = x;
u64 count = 1;
if (x < 0)
y = -1 * x;
term = y;
while (term >= tolerance) {
sum = sum + term;
count = count + 1;
term = drm_fixp_mul(term, div64_s64(y, count));
}
if (x < 0)
sum = drm_fixp_div(1, sum);
return sum;
}
#endif