1 /*
2  * Copyright 2009 Red Hat Inc.
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included in
12  * all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
17  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
20  * OTHER DEALINGS IN THE SOFTWARE.
21  *
22  * Authors: Dave Airlie
23  *          Christian König
24  */
25 #ifndef DRM_FIXED_H
26 #define DRM_FIXED_H
27 
28 #include <linux/math64.h>
29 
30 typedef union dfixed {
31 	u32 full;
32 } fixed20_12;
33 
34 
35 #define dfixed_const(A) (u32)(((A) << 12))/*  + ((B + 0.000122)*4096)) */
36 #define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
37 #define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
38 #define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
39 #define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
40 #define dfixed_init(A) { .full = dfixed_const((A)) }
41 #define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
42 #define dfixed_trunc(A) ((A).full >> 12)
43 #define dfixed_frac(A) ((A).full & ((1 << 12) - 1))
44 
dfixed_floor(fixed20_12 A)45 static inline u32 dfixed_floor(fixed20_12 A)
46 {
47 	u32 non_frac = dfixed_trunc(A);
48 
49 	return dfixed_const(non_frac);
50 }
51 
dfixed_ceil(fixed20_12 A)52 static inline u32 dfixed_ceil(fixed20_12 A)
53 {
54 	u32 non_frac = dfixed_trunc(A);
55 
56 	if (A.full > dfixed_const(non_frac))
57 		return dfixed_const(non_frac + 1);
58 	else
59 		return dfixed_const(non_frac);
60 }
61 
dfixed_div(fixed20_12 A,fixed20_12 B)62 static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
63 {
64 	u64 tmp = ((u64)A.full << 13);
65 
66 	do_div(tmp, B.full);
67 	tmp += 1;
68 	tmp /= 2;
69 	return lower_32_bits(tmp);
70 }
71 
72 #define DRM_FIXED_POINT		32
73 #define DRM_FIXED_ONE		(1ULL << DRM_FIXED_POINT)
74 #define DRM_FIXED_DECIMAL_MASK	(DRM_FIXED_ONE - 1)
75 #define DRM_FIXED_DIGITS_MASK	(~DRM_FIXED_DECIMAL_MASK)
76 #define DRM_FIXED_EPSILON	1LL
77 #define DRM_FIXED_ALMOST_ONE	(DRM_FIXED_ONE - DRM_FIXED_EPSILON)
78 
drm_int2fixp(int a)79 static inline s64 drm_int2fixp(int a)
80 {
81 	return ((s64)a) << DRM_FIXED_POINT;
82 }
83 
drm_fixp2int(s64 a)84 static inline int drm_fixp2int(s64 a)
85 {
86 	return ((s64)a) >> DRM_FIXED_POINT;
87 }
88 
drm_fixp2int_ceil(s64 a)89 static inline int drm_fixp2int_ceil(s64 a)
90 {
91 	if (a > 0)
92 		return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
93 	else
94 		return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
95 }
96 
drm_fixp_msbset(s64 a)97 static inline unsigned drm_fixp_msbset(s64 a)
98 {
99 	unsigned shift, sign = (a >> 63) & 1;
100 
101 	for (shift = 62; shift > 0; --shift)
102 		if (((a >> shift) & 1) != sign)
103 			return shift;
104 
105 	return 0;
106 }
107 
drm_fixp_mul(s64 a,s64 b)108 static inline s64 drm_fixp_mul(s64 a, s64 b)
109 {
110 	unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
111 	s64 result;
112 
113 	if (shift > 61) {
114 		shift = shift - 61;
115 		a >>= (shift >> 1) + (shift & 1);
116 		b >>= shift >> 1;
117 	} else
118 		shift = 0;
119 
120 	result = a * b;
121 
122 	if (shift > DRM_FIXED_POINT)
123 		return result << (shift - DRM_FIXED_POINT);
124 
125 	if (shift < DRM_FIXED_POINT)
126 		return result >> (DRM_FIXED_POINT - shift);
127 
128 	return result;
129 }
130 
drm_fixp_div(s64 a,s64 b)131 static inline s64 drm_fixp_div(s64 a, s64 b)
132 {
133 	unsigned shift = 62 - drm_fixp_msbset(a);
134 	s64 result;
135 
136 	a <<= shift;
137 
138 	if (shift < DRM_FIXED_POINT)
139 		b >>= (DRM_FIXED_POINT - shift);
140 
141 	result = div64_s64(a, b);
142 
143 	if (shift > DRM_FIXED_POINT)
144 		return result >> (shift - DRM_FIXED_POINT);
145 
146 	return result;
147 }
148 
drm_fixp_from_fraction(s64 a,s64 b)149 static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
150 {
151 	s64 res;
152 	bool a_neg = a < 0;
153 	bool b_neg = b < 0;
154 	u64 a_abs = a_neg ? -a : a;
155 	u64 b_abs = b_neg ? -b : b;
156 	u64 rem;
157 
158 	/* determine integer part */
159 	u64 res_abs  = div64_u64_rem(a_abs, b_abs, &rem);
160 
161 	/* determine fractional part */
162 	{
163 		u32 i = DRM_FIXED_POINT;
164 
165 		do {
166 			rem <<= 1;
167 			res_abs <<= 1;
168 			if (rem >= b_abs) {
169 				res_abs |= 1;
170 				rem -= b_abs;
171 			}
172 		} while (--i != 0);
173 	}
174 
175 	/* round up LSB */
176 	{
177 		u64 summand = (rem << 1) >= b_abs;
178 
179 		res_abs += summand;
180 	}
181 
182 	res = (s64) res_abs;
183 	if (a_neg ^ b_neg)
184 		res = -res;
185 	return res;
186 }
187 
drm_fixp_exp(s64 x)188 static inline s64 drm_fixp_exp(s64 x)
189 {
190 	s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
191 	s64 sum = DRM_FIXED_ONE, term, y = x;
192 	u64 count = 1;
193 
194 	if (x < 0)
195 		y = -1 * x;
196 
197 	term = y;
198 
199 	while (term >= tolerance) {
200 		sum = sum + term;
201 		count = count + 1;
202 		term = drm_fixp_mul(term, div64_s64(y, count));
203 	}
204 
205 	if (x < 0)
206 		sum = drm_fixp_div(DRM_FIXED_ONE, sum);
207 
208 	return sum;
209 }
210 
211 #endif
212