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armstrong

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注册时间： 2019-04-10

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F1C100s启动应用加速：SPI启用DOUT模式（无需启用DMA）

在spl代码中，用下面的代码替代sys_spi_flash_read函数，就可以最大速度加载app到ram执行。
我的AHB频率是200MHZ，SPI配置为50Mhz（100Mhz不太稳定），下面的代码启用DOUT模式传输，所以理论读取速度是12.5MB/秒。
BROM加载SPL大约150ms，而这段代码加载3MB的app代码仅需250ms，总共400毫秒就能启动3MB的应用程序。

void sys_spi_flash_read_dualout(int addr, void* buf, int count)
{
  uint32_t reg_base = 0x01c05000;
  uint8_t* rxbuf = buf;
  uint8_t tx[5];
  int n, i, c;

  n = 0;
  tx[n++] = 0x3b;   // fast read dual-output
  tx[n++] = (uint8_t)(addr >> 16);
  tx[n++] = (uint8_t)(addr >> 8);
  tx[n++] = (uint8_t)(addr >> 0);
  tx[n++] = 0;
  sys_spi_select();
  write32(reg_base + SPI_MBC, n);
  write32(reg_base + SPI_MTC, n);
  write32(reg_base + SPI_BCC, n);
  for (i = 0; i < n; i++) {
    write8(reg_base + SPI_TXD, tx[i]);
  }
  write32(reg_base + SPI_TCR, read32(reg_base + SPI_TCR) | (1u << 31));
  while (read32(reg_base + SPI_TCR) & (1u << 31));
  write32(reg_base + SPI_FCR, read32(reg_base + SPI_FCR) | 0x80008000u);
  while (count > 0) {
    n = ((count <= 4096) ? count : 4096);
    write32(reg_base + SPI_MBC, n);
    write32(reg_base + SPI_MTC, 0);
    write32(reg_base + SPI_BCC, (1 << 28)); // dual-mode
    write32(reg_base + SPI_TCR, read32(reg_base + SPI_TCR) | (1u << 31));
    for (i = n; i > 0;) {
      // 这里代码看起来很累赘，但是这样却能快速读空RXFIFO！
      if ((c = (read32(reg_base + SPI_FSR) & 0xff)) > 0) {
        i -= c;
        while (c-- > 0) {
          *rxbuf++ = read8(reg_base + SPI_RXD);
        }
      }
    }
    count -= n;
  }
  sys_spi_deselect();
}