/* tonepcm.c — 直开 /dev/snd/pcmC0D0p 写 N 秒正弦并计时（不需要耳朵的 DAC 时钟验证）：
 * 若写 5s PCM 的墙钟 ≈5s（扣除缓冲），说明硬件时钟在走、DMA 在消费；
 * 若瞬间返回，说明硬件没在走（静音根因在时钟/电源域，不在数据）。
 * 用法: tonepcm [sec] [freq]   静态 mipsel。 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <sys/ioctl.h>
#include <sound/asound.h>

static void pmask(struct snd_mask *m, unsigned bit) { m->bits[bit / 32] |= 1u << (bit % 32); }
static void pivset(struct snd_interval *iv, unsigned val)
{
    iv->min = iv->max = val; iv->integer = 1;
    iv->openmin = iv->openmax = 0; iv->empty = 0;
}
static long long now_ms(void)
{
    struct timespec ts; clock_gettime(CLOCK_MONOTONIC, &ts);
    return (long long)ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
}

int main(int argc, char **argv)
{
    int sec = argc > 1 ? atoi(argv[1]) : 5;
    int freq = argc > 2 ? atoi(argv[2]) : 440;
    int rate = 44100, ch = 2;

    int fd = open("/dev/snd/pcmC0D0p", O_RDWR);
    if (fd < 0) { printf("open pcmC0D0p fail\n"); return 1; }

    struct snd_pcm_hw_params p;
    memset(&p, 0, sizeof p);
    pmask(&p.masks[SNDRV_PCM_HW_PARAM_ACCESS - SNDRV_PCM_HW_PARAM_FIRST_MASK],
          SNDRV_PCM_ACCESS_RW_INTERLEAVED);
    pmask(&p.masks[SNDRV_PCM_HW_PARAM_FORMAT - SNDRV_PCM_HW_PARAM_FIRST_MASK],
          SNDRV_PCM_FORMAT_S16_LE);
    pmask(&p.masks[SNDRV_PCM_HW_PARAM_SUBFORMAT - SNDRV_PCM_HW_PARAM_FIRST_MASK],
          SNDRV_PCM_SUBFORMAT_STD);
    pivset(&p.intervals[SNDRV_PCM_HW_PARAM_CHANNELS - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL], ch);
    pivset(&p.intervals[SNDRV_PCM_HW_PARAM_RATE - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL], rate);
    p.rmask = ~0u;
    if (ioctl(fd, SNDRV_PCM_IOCTL_HW_PARAMS, &p) != 0) { printf("HW_PARAMS fail\n"); close(fd); return 1; }
    printf("HW_PARAMS ok (rate interval now [%u,%u])\n",
           p.intervals[SNDRV_PCM_HW_PARAM_RATE - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL].min,
           p.intervals[SNDRV_PCM_HW_PARAM_RATE - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL].max);
    if (ioctl(fd, SNDRV_PCM_IOCTL_PREPARE, 0) != 0) { printf("PREPARE fail\n"); close(fd); return 1; }

    /* 生成 1 秒正弦（整数查表近似：简单累加相位，定点幅度 0.3 满幅） */
    int frames1s = rate;
    short *buf = malloc((size_t)frames1s * ch * 2);
    for (int i = 0; i < frames1s; i++) {
        /* 粗略正弦：三角波即可（验证用） */
        int period = rate / freq;
        int ph = i % period;
        int v = (ph < period / 2) ? (ph * 4 - period) : (3 * period - ph * 4);
        short s = (short)(v * 9830 / period);   /* ~0.3 * 32767 */
        buf[i * 2] = s; buf[i * 2 + 1] = s;
    }

    long long t0 = now_ms();
    long long written = 0;
    for (int s2 = 0; s2 < sec; s2++) {
        ssize_t w = write(fd, buf, (size_t)frames1s * ch * 2);
        if (w <= 0) { printf("write fail at sec %d (ret=%zd)\n", s2, w); break; }
        written += w;
    }
    long long el = now_ms() - t0;
    long long bytes = (long long)sec * frames1s * ch * 2;
    printf("wrote %lld/%lld bytes in %lld ms (expected ~%d ms if hw clocking; instant = clock dead)\n",
           written, bytes, el, sec * 1000);

    struct snd_pcm_status st;
    memset(&st, 0, sizeof st);
    if (ioctl(fd, SNDRV_PCM_IOCTL_STATUS, &st) == 0)
        printf("STATUS: state=%d avail=%lu\n", st.state, (unsigned long)st.avail);
    close(fd);
    return 0;
}