DRC: math: Replace exponential function for performance

For DRC performance, replace "exp_small_fixed()" with "sofm_exp_int32()".
Included supporting change to include "sofm_exp_int32()" within exp_fixed()
and removed "exp_small_fixed()" from future use.

Signed-off-by: shastry <malladi.sastry@intel.com>

src/audio/Kconfig

@@ -278,8 +278,8 @@ config COMP_DRC
 	bool "Dynamic Range Compressor component"
 	select CORDIC_FIXED
 	select NUMBERS_NORM
-	select MATH_DECIBELS
 	select COMP_BLOB
+	select MATH_EXP
 	default n
 	help
 	  Select for Dynamic Range Compressor (DRC) component. A DRC can be used

src/audio/drc/drc_generic.c

@@ -10,6 +10,7 @@
 #include <sof/audio/drc/drc_math.h>
 #include <sof/audio/format.h>
 #include <sof/math/decibels.h>
+#include <sof/math/exp_fcn.h>
 #include <sof/math/numbers.h>
 #include <stdint.h>
 
@@ -35,7 +36,7 @@ static int32_t knee_curveK(const struct sof_drc_params *p, int32_t x)
 	 *	 beta = -expf(k * linear_threshold) / k
 	 *	 gamma = -k * x
 	 */
-	knee_exp_gamma = exp_fixed(Q_MULTSR_32X32((int64_t)x, -p->K, 31, 20, 27)); /* Q12.20 */
+	knee_exp_gamma = sofm_exp_fixed(Q_MULTSR_32X32((int64_t)x, -p->K, 31, 20, 27)); /* Q12.20 */
 	return p->knee_alpha + Q_MULTSR_32X32((int64_t)p->knee_beta, knee_exp_gamma, 24, 20, 24);
 }
 
@@ -65,8 +66,10 @@ static int32_t volume_gain(const struct sof_drc_params *p, int32_t x)
 		 * => y/x = ratio_base * x^(s - 1)
 		 * => y/x = ratio_base * e^(log(x) * (s - 1))
 		 */
-		exp_knee = exp_fixed(Q_MULTSR_32X32((int64_t)drc_log_fixed(Q_SHIFT_RND(x, 31, 26)),
-						    (p->slope - ONE_Q30), 26, 30, 27)); /* Q12.20 */
+		exp_knee = sofm_exp_fixed(
+					Q_MULTSR_32X32((int64_t)
+					drc_log_fixed(Q_SHIFT_RND(x, 31, 26)),
+					(p->slope - ONE_Q30), 26, 30, 27)); /* Q12.20 */
 		y = Q_MULTSR_32X32((int64_t)p->ratio_base, exp_knee, 30, 20, 30);
 	}
 

src/audio/drc/drc_hifi3.c

@@ -10,6 +10,7 @@
 #include <sof/audio/drc/drc_math.h>
 #include <sof/audio/format.h>
 #include <sof/math/decibels.h>
+#include <sof/math/exp_fcn.h>
 #include <sof/math/numbers.h>
 #include <stdint.h>
 
@@ -41,7 +42,7 @@ static int32_t knee_curveK(const struct sof_drc_params *p, int32_t x)
 	 *	 gamma = -k * x
 	 */
 	gamma = drc_mult_lshift(x, -p->K, drc_get_lshift(31, 20, 27));
-	knee_exp_gamma = exp_fixed(gamma);
+	knee_exp_gamma = sofm_exp_fixed(gamma);
 	knee_curve_k = drc_mult_lshift(p->knee_beta, knee_exp_gamma, drc_get_lshift(24, 20, 24));
 	knee_curve_k = AE_ADD32(knee_curve_k, p->knee_alpha);
 	return knee_curve_k;
@@ -77,7 +78,7 @@ static int32_t volume_gain(const struct sof_drc_params *p, int32_t x)
 		tmp = AE_SRAI32R(x, 5); /* Q1.31 -> Q5.26 */
 		tmp = drc_log_fixed(tmp); /* Q6.26 */
 		tmp2 = AE_SUB32(p->slope, ONE_Q30); /* Q2.30 */
-		exp_knee = exp_fixed(drc_mult_lshift(tmp, tmp2, drc_get_lshift(26, 30, 27)));
+		exp_knee = sofm_exp_fixed(drc_mult_lshift(tmp, tmp2, drc_get_lshift(26, 30, 27)));
 		y = drc_mult_lshift(p->ratio_base, exp_knee, drc_get_lshift(30, 20, 30));
 	}
 

src/audio/drc/drc_math_generic.c

@@ -7,6 +7,7 @@
 #include <sof/audio/drc/drc_math.h>
 #include <sof/audio/format.h>
 #include <sof/math/decibels.h>
+#include <sof/math/exp_fcn.h>
 #include <sof/math/numbers.h>
 #include <sof/math/trig.h>
 
@@ -219,8 +220,6 @@ inline int32_t drc_inv_fixed(int32_t x, int32_t precision_x, int32_t precision_y
 #undef qc
 }
 
-#endif /* DRC_GENERIC */
-
 /*
  * Input x is Q6.26; valid range: (0.0, 32.0); x <= 0 is not supported
  *       y is Q2.30: (-2.0, 2.0)
@@ -233,8 +232,8 @@ inline int32_t drc_pow_fixed(int32_t x, int32_t y)
 		return 0;
 
 	/* x^y = expf(y * log(x)) */
-	return exp_fixed(q_mult(y, drc_log_fixed(x), 30, 26, 27));
+	return sofm_exp_fixed(q_mult(y, drc_log_fixed(x), 30, 26, 27));
 }
-
+#endif
 #undef q_multq
 #undef q_mult

src/include/sof/math/decibels.h

@@ -11,12 +11,6 @@
 
 #include <stdint.h>
 
-#define EXP_FIXED_INPUT_QY 27
-#define EXP_FIXED_OUTPUT_QY 20
-#define DB2LIN_FIXED_INPUT_QY 24
-#define DB2LIN_FIXED_OUTPUT_QY 20
-
-int32_t exp_fixed(int32_t x); /* Input is Q5.27, output is Q12.20 */
 int32_t db2lin_fixed(int32_t x); /* Input is Q8.24, output is Q12.20 */
 
 #endif /* __SOF_MATH_DECIBELS_H__ */

src/include/sof/math/exp_fcn.h

@@ -26,6 +26,6 @@
 
 #endif
 
-int32_t sofm_exp_int32(int32_t x);
-
+int32_t sofm_exp_int32(int32_t x); /* Input is Q4.28, Output is Q9.23 */
+int32_t sofm_exp_fixed(int32_t x); /* Input is Q5.27, output is Q12.20 */
 #endif

src/math/Kconfig

@@ -47,6 +47,15 @@ config MATH_EXP
 	  an input range of -5 to +5 gives positive numbers between 0.00673794699908547 and
 	  148.413159102577. The precision of this function is 1e-4.
 
+config MATH_EXP_SMALL_FXD
+	bool "Small Exponential functions"
+	default n
+	help
+	  By selecting this, the 32-bit exp_small_fixed() function can be used to calculate
+	  exponential values. With a mean thdn of -131.205(dBc), an exponential function with
+	  an input range of -2 to +2 gives positive numbers between 0.135335255 and
+	  7.38905609. The precision of this function is 1e-6.
+
 config NATURAL_LOGARITHM_FIXED
 	bool "Natural Logarithm function"
 	default n

src/math/auditory/auditory.c

@@ -8,6 +8,7 @@
 #include <rtos/alloc.h>
 #include <sof/math/auditory.h>
 #include <sof/math/decibels.h>
+#include <sof/math/exp_fcn.h>
 #include <sof/math/fft.h>
 #include <sof/math/log.h>
 #include <sof/math/numbers.h>
@@ -80,7 +81,7 @@ int16_t psy_mel_to_hz(int16_t mel)
 		return 0;
 
 	exp_arg = Q_MULTSR_32X32((int64_t)mel, ONE_OVER_MELDIV_Q31, 2, 31, 27);
-	exp = exp_fixed(exp_arg)  - ONE_Q20;
+	exp = sofm_exp_fixed(exp_arg)  - ONE_Q20;
 	hz = Q_MULTSR_32X32((int64_t)exp, 700, 20, 0, 0);
 	return hz;
 }

src/math/decibels.c

@@ -6,47 +6,11 @@
 
 #include <sof/audio/format.h>
 #include <sof/math/decibels.h>
+#include <sof/math/exp_fcn.h>
 #include <stdint.h>
 
-#define ONE_Q20         Q_CONVERT_FLOAT(1.0, 20)	  /* Use Q12.20 */
-#define ONE_Q23         Q_CONVERT_FLOAT(1.0, 23)	  /* Use Q9.23 */
-#define TWO_Q27         Q_CONVERT_FLOAT(2.0, 27)	  /* Use Q5.27 */
-#define MINUS_TWO_Q27   Q_CONVERT_FLOAT(-2.0, 27)	  /* Use Q5.27 */
 #define LOG10_DIV20_Q27 Q_CONVERT_FLOAT(0.1151292546, 27) /* Use Q5.27 */
 
-/* Exponent function for small values of x. This function calculates
- * fairly accurately exponent for x in range -2.0 .. +2.0. The iteration
- * uses first 11 terms of Taylor series approximation for exponent
- * function. With the current scaling the numerator just remains under
- * 64 bits with the 11 terms.
- *
- * See https://en.wikipedia.org/wiki/Exponential_function#Computation
- *
- * The input is Q3.29
- * The output is Q9.23
- */
-
-static int32_t exp_small_fixed(int32_t x)
-{
-	int64_t p;
-	int64_t num = Q_SHIFT_RND(x, 29, 23);
-	int32_t y0 = (int32_t)num;
-	int32_t den = 1;
-	int32_t inc;
-	int k;
-
-	/* Numerator is x^k, denominator is k! */
-	for (k = 2; k < 12; k++) {
-		p = num * x; /* Q9.23 x Q3.29 -> Q12.52 */
-		num = Q_SHIFT_RND(p, 52, 23);
-		den = den * k;
-		inc = (int32_t)(num / den);
-		y0 += inc;
-	}
-
-	return y0 + ONE_Q23;
-}
-
 /* Decibels to linear conversion: The function uses exp() to calculate
  * the linear value. The argument is multiplied by log(10)/20 to
  * calculate equivalent of 10^(db/20).
@@ -68,50 +32,5 @@ int32_t db2lin_fixed(int32_t db)
 
 	/* Q8.24 x Q5.27, result needs to be Q5.27 */
 	arg = (int32_t)Q_MULTSR_32X32((int64_t)db, LOG10_DIV20_Q27, 24, 27, 27);
-	return exp_fixed(arg);
-}
-
-/* Fixed point exponent function for approximate range -11.5 .. 7.6
- * that corresponds to decibels range -100 .. +66 dB.
- *
- * The functions uses rule exp(x) = exp(x/2) * exp(x/2) to reduce
- * the input argument for private small value exp() function that is
- * accurate with input range -2.0 .. +2.0. The number of possible
- * divisions by 2 is computed into variable n. The returned value is
- * exp()^(2^n).
- *
- * Input  is Q5.27, -16.0 .. +16.0, but note the input range limitation
- * Output is Q12.20, 0.0 .. +2048.0
- */
-
-int32_t exp_fixed(int32_t x)
-{
-	int32_t xs;
-	int32_t y;
-	int32_t y0;
-	int i;
-	int n = 0;
-
-	if (x < Q_CONVERT_FLOAT(-11.5, 27))
-		return 0;
-
-	if (x > Q_CONVERT_FLOAT(7.6245, 27))
-		return INT32_MAX;
-
-	/* x is Q5.27 */
-	xs = x;
-	while (xs >= TWO_Q27 || xs <= MINUS_TWO_Q27) {
-		xs >>= 1;
-		n++;
-	}
-
-	/* exp_small_fixed() input is Q3.29, while x1 is Q5.27
-	 * exp_small_fixed() output is Q9.23, while y0 is Q12.20
-	 */
-	y0 = Q_SHIFT_RND(exp_small_fixed(Q_SHIFT_LEFT(xs, 27, 29)), 23, 20);
-	y = ONE_Q20;
-	for (i = 0; i < (1 << n); i++)
-		y = (int32_t)Q_MULTSR_32X32((int64_t)y, y0, 20, 20, 20);
-
-	return y;
+	return sofm_exp_fixed(arg);
 }

src/math/exp_fcn.c

@@ -6,6 +6,9 @@
  *
  */
 
+#include <sof/audio/drc/drc_plat_conf.h>
+#include <sof/math/decibels.h>
+#include <sof/audio/format.h>
 #include <sof/math/exp_fcn.h>
 #include <sof/math/numbers.h>
 #include <sof/common.h>
@@ -20,7 +23,7 @@
 #define SOFM_BIT_MASK_Q62P2 0x4000000000000000LL
 #define SOFM_CONVERG_ERROR 28823037607936LL	// error smaller than 1e-4,1/2 ^ -44.7122876200884
 #define SOFM_BIT_MASK_LOW_Q27P5 0x8000000
-#define SOFM_QUOTIENT_SCALE BIT(30)
+#define SOFM_QUOTIENT_SCALE 0x400000000
 #define SOFM_TERMS_Q23P9 8388608
 #define SOFM_LSHIFT_BITS 8192
 
@@ -176,6 +179,7 @@ static inline int64_t lomul_s64_sr_sat_near(int64_t a, int64_t b)
  *| 32 | 28  |  1    | 32 | 23 |   0   | 4.28   | 9.23   |
  *+------------------+-----------------+--------+--------+
  */
+//static inline int32_t sofm_exp_int32(int32_t x)
 int32_t sofm_exp_int32(int32_t x)
 {
 	uint64_t ou0Hi;
@@ -217,4 +221,52 @@ int32_t sofm_exp_int32(int32_t x)
 	}
 	return ts;
 }
+
+#define ONE_Q20         Q_CONVERT_FLOAT(1.0, 20)	  /* Use Q12.20 */
+#define TWO_Q27         Q_CONVERT_FLOAT(2.0, 27)	  /* Use Q5.27 */
+#define MINUS_TWO_Q27   Q_CONVERT_FLOAT(-2.0, 27)	  /* Use Q5.27 */
+
+/* Fixed point exponent function for approximate range -11.5 .. 7.6
+ * that corresponds to decibels range -100 .. +66 dB.
+ *
+ * The functions uses rule exp(x) = exp(x/2) * exp(x/2) to reduce
+ * the input argument for private small value exp() function that is
+ * accurate with input range -2.0 .. +2.0. The number of possible
+ * divisions by 2 is computed into variable n. The returned value is
+ * exp()^(2^n).
+ *
+ * Input  is Q5.27, -16.0 .. +16.0, but note the input range limitation
+ * Output is Q12.20, 0.0 .. +2048.0
+ */
+int32_t sofm_exp_fixed(int32_t x)
+{
+	int32_t xs;
+	int32_t y;
+	int32_t y0;
+	int i;
+	int n = 0;
+
+	if (x < Q_CONVERT_FLOAT(-11.5, 27))
+		return 0;
+
+	if (x > Q_CONVERT_FLOAT(7.6245, 27))
+		return INT32_MAX;
+
+	/* x is Q5.27 */
+	xs = x;
+	while (xs >= TWO_Q27 || xs <= MINUS_TWO_Q27) {
+		xs >>= 1;
+		n++;
+	}
+
+	/* sofm_exp_int32() input is Q4.28, while x1 is Q5.27
+	 * sofm_exp_int32() output is Q9.23, while y0 is Q12.20
+	 */
+	y0 = Q_SHIFT_RND(sofm_exp_int32(Q_SHIFT_LEFT(xs, 27, 28)), 23, 20);
+	y = ONE_Q20;
+	for (i = 0; i < (1 << n); i++)
+		y = (int32_t)Q_MULTSR_32X32((int64_t)y, y0, 20, 20, 20);
+
+	return y;
+}
 #endif