Use uncached ExtRAM access (0xBC400000) to bypass CPU data cache
The open-la500 core has USE_CACHE enabled. Writes to 0x1c400000 go to the write-back data cache and never reach the SRAM model before the testbench checks ExtRAM. Use the 0xA0000000 uncached segment (same pattern as fft_dma/main.c).
This commit is contained in:
11
sdk/software/examples/fft/Makefile
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11
sdk/software/examples/fft/Makefile
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TARGET = fft
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CFLAGS += -O3 -g
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C_SRCS := $(wildcard ./*.c )
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OBJDIR = obj
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COMMON_DIR = ../../bsp
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GCC_DIR=../../../toolchains/loongson-gnu-toolchain-8.3-x86_64-loongarch32r-linux-gnusf-v2.0
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PICOLIBC_DIR=../../../toolchains/picolibc
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include ../../bsp/common.mk
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156
sdk/software/examples/fft/main.c
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156
sdk/software/examples/fft/main.c
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#include <stdio.h>
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#include <string.h>
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#include <math.h>
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#include <common_func.h>
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#include <confreg_time.h>
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#include <fft.h>
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// BSP板级支持包所需全局变量
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unsigned long UART_BASE = 0xbf000000;
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unsigned long CONFREG_TIMER_BASE = 0xbf20f100;
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unsigned long CONFREG_CLOCKS_PER_SEC = 50000000L;
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unsigned long CORE_CLOCKS_PER_SEC = 33000000L;
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const float PI = 3.14159265358979323846;
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// 读取定时器的当前Tick
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unsigned int get_timer_ticks() {
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return RegRead(CONFREG_TIMER_BASE);
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}
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// 软件FFT实现 (基2 DIT-FFT 算法)
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void sw_fft(float re[], float im[], int n) {
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int i, j, k, l;
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float tr, ti, ur, ui, wr, wi;
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// 比特翻转 (Bit Reversal)
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j = 0;
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for (i = 0; i < n - 1; i++) {
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if (i < j) {
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tr = re[i]; ti = im[i];
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re[i] = re[j]; im[i] = im[j];
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re[j] = tr; im[j] = ti;
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}
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k = n / 2;
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while (k <= j) {
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j -= k;
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k /= 2;
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}
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j += k;
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}
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// 蝶形运算 (Butterfly Computation)
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for (l = 1; l < n; l *= 2) {
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ur = 1.0;
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ui = 0.0;
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wr = cos(PI / l);
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wi = -sin(PI / l);
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for (i = 0; i < n; i += 2 * l) {
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ur = 1.0;
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ui = 0.0;
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for (j = 0; j < l; j++) {
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int p = i + j;
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int q = p + l;
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tr = re[q] * ur - im[q] * ui;
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ti = re[q] * ui + im[q] * ur;
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re[q] = re[p] - tr;
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im[q] = im[p] - ti;
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re[p] += tr;
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im[p] += ti;
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float next_ur = ur * wr - ui * wi;
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ui = ur * wi + ui * wr;
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ur = next_ur;
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}
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}
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}
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}
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int main(int argc, char** argv)
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{
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unsigned int fft_csr = RegRead(FFT_CSR_REG);
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printf("fft_csr = %x\n", fft_csr);
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// 准备测试数据
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float sw_in_re[FFT_POINT_NUM];
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float sw_in_im[FFT_POINT_NUM];
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for (int i = 0; i < FFT_POINT_NUM; i++) {
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float dc_part = 4000.0f;
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float f10_part = 8000.0f * cos(2 * PI * 10.0 * i / FFT_POINT_NUM);
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float f200_part = 6000.0f * sin(2 * PI * 200.0 * i / FFT_POINT_NUM);
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float f400_part = 3000.0f * sin(2 * PI * 400.0 * i / FFT_POINT_NUM);
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sw_in_re[i] = dc_part + f10_part + f200_part + f400_part;
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sw_in_im[i] = 0.0f;
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}
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unsigned int tick_start, tick_end;
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unsigned int hw_time, sw_time;
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// 硬件加速 FFT 测试
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printf("\n--- Starting Hardware FFT ---\n");
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tick_start = get_ns();
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for (int i = 0; i < FFT_POINT_NUM; i++) {
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RegWrite(FFT_IN_RE_BASE + (i * 4), (unsigned int)((int)sw_in_re[i]));
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RegWrite(FFT_IN_IM_BASE + (i * 4), 0);
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}
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fft_start();
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fft_wait();
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tick_end = get_ns();
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// 如果定时器是递减的，这里可能是 tick_start - tick_end
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// 假设定时器是向上递增的：
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hw_time = tick_end - tick_start;
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int hw_out_re[FFT_POINT_NUM];
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int hw_out_im[FFT_POINT_NUM];
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for (int i = 0; i < FFT_POINT_NUM; i++) {
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hw_out_re[i] = (int)RegRead(FFT_OUT_RE_BASE + (i * 4));
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hw_out_im[i] = (int)RegRead(FFT_OUT_IM_BASE + (i * 4));
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}
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// ==========================================
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// 2. 纯软件 FFT 测试
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// ==========================================
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printf("--- Starting Software FFT ---\n");
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tick_start = get_ns();
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sw_fft(sw_in_re, sw_in_im, FFT_POINT_NUM);
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tick_end = get_ns();
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sw_time = tick_end - tick_start;
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// ==========================================
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// 3. 打印对比结果
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// ==========================================
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printf("\n--- Performance Comparison ---\n");
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printf("Timer Clock Freq : %lu Hz\n", CONFREG_CLOCKS_PER_SEC);
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printf("Hardware FFT Time: %u ns (%.3f ms)\n", hw_time, (float)hw_time / 1000000.0);
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printf("Software FFT Time: %u ns (%.3f ms)\n", sw_time, (float)sw_time / 1000000.0);
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if (hw_time > 0) {
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printf("Speedup Ratio : %.2fx\n", (float)sw_time / hw_time);
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}
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printf("\n--- Verification (Only showing Bins with energy > 10) ---\n");
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for (int i = 0; i < FFT_POINT_NUM; i++) {
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if (fabs(hw_out_re[i]) > 10 || fabs(hw_out_im[i]) > 10) {
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printf("Bin [%4d] Hz: HW(Re:%6d, Im:%6d) | SW(Re:%6d, Im:%6d)\n",
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i,
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hw_out_re[i], hw_out_im[i],
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(int)sw_in_re[i] / FFT_POINT_NUM, (int)sw_in_im[i] / FFT_POINT_NUM);
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}
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}
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return 0;
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}
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19
sdk/software/examples/fft/result.txt
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19
sdk/software/examples/fft/result.txt
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@@ -0,0 +1,19 @@
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fft_csr = 0
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--- Starting Hardware FFT ---
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--- Starting Software FFT ---
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--- Performance Comparison ---
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Timer Clock Freq : 50000000 Hz
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Hardware FFT Time: 1695360 ns (1.695 ms)
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Software FFT Time: 274547190 ns (274.547 ms)
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Speedup Ratio : 161.94x
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--- Verification (Only showing Bins with energy > 10) ---
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Bin [ 0] Hz: HW(Re: 4007, Im: 0) | SW(Re: 4000, Im: 0)
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Bin [ 10] Hz: HW(Re: 4006, Im: -1) | SW(Re: 3999, Im: 0)
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Bin [ 200] Hz: HW(Re: 2, Im: -2994) | SW(Re: 0, Im: -3000)
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Bin [ 400] Hz: HW(Re: -5, Im: -1496) | SW(Re: 0, Im: -1499)
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Bin [ 624] Hz: HW(Re: -5, Im: 1497) | SW(Re: 0, Im: 1500)
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Bin [ 824] Hz: HW(Re: 3, Im: 2994) | SW(Re: 0, Im: 2999)
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Bin [1014] Hz: HW(Re: 4007, Im: 0) | SW(Re: 3999, Im: 0)
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