2 * Copyright (c) 2010 Broadcom Corporation
4 * Permission to use, copy, modify, and/or distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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14 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 #include "phy_qmath.h"
20 Description: This function make 16 bit unsigned multiplication. To fit the output into
21 16 bits the 32 bit multiplication result is right shifted by 16 bits.
23 u16 qm_mulu16(u16 op1, u16 op2)
25 return (u16) (((u32) op1 * (u32) op2) >> 16);
29 Description: This function make 16 bit multiplication and return the result in 16 bits.
30 To fit the multiplication result into 16 bits the multiplication result is right shifted by
31 15 bits. Right shifting 15 bits instead of 16 bits is done to remove the extra sign bit formed
32 due to the multiplication.
33 When both the 16bit inputs are 0x8000 then the output is saturated to 0x7fffffff.
35 s16 qm_muls16(s16 op1, s16 op2)
38 if (op1 == (s16) 0x8000 && op2 == (s16) 0x8000) {
41 result = ((s32) (op1) * (s32) (op2));
43 return (s16) (result >> 15);
47 Description: This function add two 32 bit numbers and return the 32bit result.
48 If the result overflow 32 bits, the output will be saturated to 32bits.
50 s32 qm_add32(s32 op1, s32 op2)
54 if (op1 < 0 && op2 < 0 && result > 0) {
56 } else if (op1 > 0 && op2 > 0 && result < 0) {
63 Description: This function add two 16 bit numbers and return the 16bit result.
64 If the result overflow 16 bits, the output will be saturated to 16bits.
66 s16 qm_add16(s16 op1, s16 op2)
69 s32 temp = (s32) op1 + (s32) op2;
70 if (temp > (s32) 0x7fff) {
71 result = (s16) 0x7fff;
72 } else if (temp < (s32) 0xffff8000) {
73 result = (s16) 0xffff8000;
81 Description: This function make 16 bit subtraction and return the 16bit result.
82 If the result overflow 16 bits, the output will be saturated to 16bits.
84 s16 qm_sub16(s16 op1, s16 op2)
87 s32 temp = (s32) op1 - (s32) op2;
88 if (temp > (s32) 0x7fff) {
89 result = (s16) 0x7fff;
90 } else if (temp < (s32) 0xffff8000) {
91 result = (s16) 0xffff8000;
99 Description: This function make a 32 bit saturated left shift when the specified shift
100 is +ve. This function will make a 32 bit right shift when the specified shift is -ve.
101 This function return the result after shifting operation.
103 s32 qm_shl32(s32 op, int shift)
110 else if (shift < -31)
113 for (i = 0; i < shift; i++) {
114 result = qm_add32(result, result);
117 result = result >> (-shift);
123 Description: This function make a 16 bit saturated left shift when the specified shift
124 is +ve. This function will make a 16 bit right shift when the specified shift is -ve.
125 This function return the result after shifting operation.
127 s16 qm_shl16(s16 op, int shift)
134 else if (shift < -15)
137 for (i = 0; i < shift; i++) {
138 result = qm_add16(result, result);
141 result = result >> (-shift);
147 Description: This function make a 16 bit right shift when shift is +ve.
148 This function make a 16 bit saturated left shift when shift is -ve. This function
149 return the result of the shift operation.
151 s16 qm_shr16(s16 op, int shift)
153 return qm_shl16(op, -shift);
157 Description: This function return the number of redundant sign bits in a 32 bit number.
158 Example: qm_norm32(0x00000080) = 23
160 s16 qm_norm32(s32 op)
162 u16 u16extraSignBits;
166 u16extraSignBits = 0;
167 while ((op >> 31) == (op >> 30)) {
172 return u16extraSignBits;
175 /* This table is log2(1+(i/32)) where i=[0:1:31], in q.15 format */
176 static const s16 log_table[] = {
211 #define LOG_TABLE_SIZE 32 /* log_table size */
212 #define LOG2_LOG_TABLE_SIZE 5 /* log2(log_table size) */
213 #define Q_LOG_TABLE 15 /* qformat of log_table */
214 #define LOG10_2 19728 /* log10(2) in q.16 */
218 This routine takes the input number N and its q format qN and compute
219 the log10(N). This routine first normalizes the input no N. Then N is in mag*(2^x) format.
220 mag is any number in the range 2^30-(2^31 - 1). Then log2(mag * 2^x) = log2(mag) + x is computed.
221 From that log10(mag * 2^x) = log2(mag * 2^x) * log10(2) is computed.
222 This routine looks the log2 value in the table considering LOG2_LOG_TABLE_SIZE+1 MSBs.
223 As the MSB is always 1, only next LOG2_OF_LOG_TABLE_SIZE MSBs are used for table lookup.
224 Next 16 MSBs are used for interpolation.
226 N - number to which log10 has to be found.
228 log10N - address where log10(N) will be written.
229 qLog10N - address where log10N qformat will be written.
231 For accurate results input should be in normalized or near normalized form.
233 void qm_log10(s32 N, s16 qN, s16 *log10N, s16 *qLog10N)
235 s16 s16norm, s16tableIndex, s16errorApproximation;
239 /* normalize the N. */
240 s16norm = qm_norm32(N);
243 /* The qformat of N after normalization.
244 * -30 is added to treat the no as between 1.0 to 2.0
245 * i.e. after adding the -30 to the qformat the decimal point will be
246 * just rigtht of the MSB. (i.e. after sign bit and 1st MSB). i.e.
247 * at the right side of 30th bit.
249 qN = qN + s16norm - 30;
251 /* take the table index as the LOG2_OF_LOG_TABLE_SIZE bits right of the MSB */
252 s16tableIndex = (s16) (N >> (32 - (2 + LOG2_LOG_TABLE_SIZE)));
254 /* remove the MSB. the MSB is always 1 after normalization. */
256 s16tableIndex & (s16) ((1 << LOG2_LOG_TABLE_SIZE) - 1);
258 /* remove the (1+LOG2_OF_LOG_TABLE_SIZE) MSBs in the N. */
259 N = N & ((1 << (32 - (2 + LOG2_LOG_TABLE_SIZE))) - 1);
261 /* take the offset as the 16 MSBS after table index.
263 u16offset = (u16) (N >> (32 - (2 + LOG2_LOG_TABLE_SIZE + 16)));
265 /* look the log value in the table. */
266 s32log = log_table[s16tableIndex]; /* q.15 format */
268 /* interpolate using the offset. */
269 s16errorApproximation = (s16) qm_mulu16(u16offset, (u16) (log_table[s16tableIndex + 1] - log_table[s16tableIndex])); /* q.15 */
271 s32log = qm_add16((s16) s32log, s16errorApproximation); /* q.15 format */
273 /* adjust for the qformat of the N as
274 * log2(mag * 2^x) = log2(mag) + x
276 s32log = qm_add32(s32log, ((s32) -qN) << 15); /* q.15 format */
278 /* normalize the result. */
279 s16norm = qm_norm32(s32log);
281 /* bring all the important bits into lower 16 bits */
282 s32log = qm_shl32(s32log, s16norm - 16); /* q.15+s16norm-16 format */
284 /* compute the log10(N) by multiplying log2(N) with log10(2).
285 * as log10(mag * 2^x) = log2(mag * 2^x) * log10(2)
286 * log10N in q.15+s16norm-16+1 (LOG10_2 is in q.16)
288 *log10N = qm_muls16((s16) s32log, (s16) LOG10_2);
290 /* write the q format of the result. */
291 *qLog10N = 15 + s16norm - 16 + 1;