Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 210a0b9e authored by Alex Deucher's avatar Alex Deucher
Browse files

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: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 9ed36f75

include/drm/drm_fixed.h

+94 −0
Original line number Diff line number Diff line
@@ -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