龙讯桥接芯片lt9611 hdmi out audio调试

前言：
在nxp-imx8mm相关项目中用，使用龙讯的桥接芯片lt9611。在调试过程中，发现，audio挑显示器，在一些显示器上没有声音，主控的i2s clk，data信号都是输出到lt9611上的。于是在排查了一些必要条件后，把audio部分的问题归结到了lt9611 mcu的i2s接口上，即、lt9611 i2s 相关寄存器上。
1.原理图：

i2s：mclk，sclk，ws , data用示波器量都是有信号的。
2.官方提供的单片机mcu参考代码
audio部分：可以看到整个代码中，只有在函数入口初始化了lt9611的i2s相关寄存器。由于lt9611的datasheet没有找到，不知具体的寄存器代表什么意思，有点可惜，但是很确定的是，对i2s寄存器配置，打开了i2s通道。所以重点就是下面的i2s寄存器配置。

void LT9611_Audio_Init(void) //sujin
{
   
	#if 1
	if(lt9611.audio_out==audio_i2s)
	{
   
		printf("\r\nAudio inut = I2S 2ch");
	
		HDMI_WriteI2C_Byte(0xff,0x84);
		HDMI_WriteI2C_Byte(0x06,0x08);
		HDMI_WriteI2C_Byte(0x07,0x10);

        //48K sampling frequency	
		HDMI_WriteI2C_Byte(0x0f,0x2b); //0x2b: 48K, 0xab:96K
		HDMI_WriteI2C_Byte(0x34,0xd4); //CTS_N 20180823 0xd5: sclk = 32fs, 0xd4: sclk = 64fs
      
		HDMI_WriteI2C_Byte(0x35,0x00); // N value = 6144
		HDMI_WriteI2C_Byte(0x36,0x18); 
		HDMI_WriteI2C_Byte(0x37,0x00); 
		
        //96K sampling frequency	
		//HDMI_WriteI2C_Byte(0x0f,0xab); //0x2b: 48K, 0xab:96K
		//HDMI_WriteI2C_Byte(0x34,0xd4); //CTS_N 20180823 0xd5: sclk = 32fs, 0xd4: sclk = 64fs
      
		//HDMI_WriteI2C_Byte(0x35,0x00); // N value = 12288
		//HDMI_WriteI2C_Byte(0x36,0x30);
		//HDMI_WriteI2C_Byte(0x37,0x00); 


        //44.1K sampling frequency
/*
		HDMI_WriteI2C_Byte(0x0f,0x0b); //0x2b: 48K, 0xab:96K
		HDMI_WriteI2C_Byte(0x34,0xd4); //CTS_N 20180823 0xd5: sclk = 32fs, 0xd4: sclk = 64fs
      
		HDMI_WriteI2C_Byte(0x35,0x00); // N value = 6272
		HDMI_WriteI2C_Byte(0x36,0x18); 
		HDMI_WriteI2C_Byte(0x37,0x80); 
*/
	}
	
	if(lt9611.audio_out==audio_spdif)
	{
   
		printf("\r\nAudio inut = SPDIF");

		HDMI_WriteI2C_Byte(0xff,0x84);
		HDMI_WriteI2C_Byte(0x06,0x0c);
		HDMI_WriteI2C_Byte(0x07,0x10);	

		HDMI_WriteI2C_Byte(0x34,0xd4); //CTS_N
	}
	#endif
}

void LT9611_Init(void)
{
   
  u32 cnt = 0;
	//RESET_LT9611();
	LT9611_Chip_ID();
	LT9611_System_Init(); 
	
	//LT9611_RST_PD_Init(); 
	LT9611_MIPI_Input_Analog(); 
	LT9611_MIPI_Input_Digtal();

	Timer0_Delay1ms(1000);
	LT9611_Video_Check();
	
	LT9611_PLL(video);
	LT9611_MIPI_Pcr(video); //pcr setup

	LT9611_Audio_Init();
	LT9611_CSC();
	LT9611_HDCP_Init();
	LT9611_HDMI_TX_Digital(video);
	LT9611_HDMI_TX_Phy();

	LT9611_IRQ_Init();;
	//LT9611_Read_EDID();

//	LT9611_HDMI_CEC_ON(1);
//	lt9611_cec_msg_set_logical_address();
  lt9611_cec_msg_init(&lt9611_cec_msg);
	
	LT9611_Enable_Interrupts(HPD_INTERRUPT_ENABLE, 1);
  LT9611_Enable_Interrupts(VID_CHG_INTERRUPT_ENABLE, 0);
	LT9611_Enable_Interrupts(CEC_INTERRUPT_ENABLE, 1);
	
	LT9611_Frequency_Meter_Byte_Clk();
	LT9611_Dphy_debug();
	LT9611_Htotal_Sysclk();
	LT9611_Pcr_MK_Print();

	printf("\r\n==========================LT9611 Initial End===============================");
	Timer0_Delay1ms(200); //HPD have debounce, wait HPD irq.
	//while(1);
	LT9611_HDP_Interrupt_Handle();
  //lt9611_cec_msg_write_demo();
  
	while(1)
	{
   
	  if(irq_task_flag)
	  {
   
		  //print("\r\nirq task...");
		  LT9611_IRQ_Task();
		  irq_task_flag = 0;
		  set_EPI;
	  }

//    lt9611_cec_msg_mainloop(&lt9611_cec_msg);
    }
}

3.linux lt9611 驱动代码
驱动在probe后，上层调用的时候，先init部分寄存器，在hw有设置了相关的寄存器，并且对比官方参考代码，audio部分设置的寄存器还是有很大差别的。

static int rk_lt9611_audio_init(struct lt9611 *lt)
{
   
    int ret = 0;
        printk(KERN_ERR"\r\nAudio input = I2S 2ch");
        ret = lt9611_write_byte(lt, BANK_SELECT_ADDR, SYSTEM_CTRL0_BLOCK);
        if (ret) {
   
                DRM_ERROR("Failed to select SYSTEM_CTRL0_BLOCK, ret=%d\n", ret);
                return ret;
        }
//      HDMI_WriteI2C_Byte(0xff,0x82);
        ret = lt9611_write_byte(lt, RGO_HDMITX_CTRL0_OFFSET, 0x8e); //0x8e: HDMI, 0x0e:DVI
        if (ret) {
   
                DRM_ERROR("Failed to set RGO_HDMITX_CTRL0_OFFSET, ret=%d\n", ret);
                return ret;
        }
//      HDMI_WriteI2C_Byte(0xd6,0x8c);
        ret = lt9611_write_byte(lt, RGO_HDMITX_CTRL1_OFFSET, 0x04);
        if (ret) {
   
                DRM_ERROR("Failed to set RGO_HDMITX_CTRL1_OFFSET, ret=%d\n", ret);
                return ret;
        }
//      HDMI_WriteI2C_Byte(0xd7,0x04); //sync polarity
        ret = lt9611_write_byte(lt,</