mtk8127 bt sco 路径

1 mtk8127做蓝牙耳机时的系统框图

下面是bt sco的音频通道、音频codec、ap、modem等模块的连接框图。

下图是当mtk8127做handfree client时，bt sco的音频数据流走向（红色的中空箭头表示down link的语音数据流，紫色的中空箭头表示up link的语音数据流，）

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bt sco音频设备在内核空间对应的设备节点为：/dev/ebc.通过misc_register系统函数来注册struct miscdevice设备。

代码路径：

2 数据结构

接收循环buffer对应的数据结构，其中蓝牙mcu子系统往这个循环buffer队列中写，对应的写下标为：iPacket_w；而驱动上层read接口，则是从这个循环buffer队列中读，对应的读下标为：iPacket_r，并且这个读写下标都不是反卷的，都是线性增长，当需要使用反卷的效果时，只需要执行如下操作即可：btsco.pRX->iPacket_w/iPacket_r & SCO_RX_PACKET_MASK

typedef struct
{
    kal_uint8     PacketBuf[SCO_RX_PACKER_BUF_NUM][SCO_RX_PLC_SIZE + BTSCO_CVSD_PACKET_VALID_SIZE];
    kal_bool        PacketValid[SCO_RX_PACKER_BUF_NUM];
    kal_int32    iPacket_w;
    kal_int32    iPacket_r;
    kal_uint8     TempPacketBuf[BT_SCO_PACKET_180];
    kal_bool      fOverflow;
    kal_uint32      u4BufferSize;   //RX packetbuf size
} BT_SCO_RX_T;

由于驱动read是在应用所在的线程，而蓝牙mcu子系统往这个循环buffer队列中写（对应函数：AudDrv_BTCVSD_ReadFromBT）则是在中断线程中，所以他们存在同步和竞争的关系。驱动通过如下成员来控制

• 自旋锁：auddrv_BTCVSDRX_lock
• 等待队列：BTCVSD_Read_Wait_Queue/BTCVSD_read_wait_queue_flag

由于是在中断中，所以必须使用spin_lock_irqsave、spin_unlock_irqrestore形式来锁住和释放该自旋锁。

类似的发送循环buffer对应的数据结构为：

typedef struct
{
    kal_uint8     PacketBuf[SCO_TX_PACKER_BUF_NUM][SCO_TX_ENCODE_SIZE];
    kal_int32    iPacket_w;
    kal_int32    iPacket_r;
    kal_uint8     TempPacketBuf[BT_SCO_PACKET_180];
    kal_bool      fUnderflow;
    kal_uint32      u4BufferSize; //TX packetbuf size
} BT_SCO_TX_T;

其中蓝牙的mcu子系统往这个循环buffer队列中读，对应的读下标为：iPacket_r；而驱动上层的write接口，则是从这个循环buffer队列中写，对应的写下表为：iPacket_w，同样这个读写下标都是线性增长的。当需要使用反卷的效果时，只需要执行如下操作即可：btsco.pTX->iPacket_w/iPacket_r & & SCO_TX_PACKET_MASK

由于驱动write是在应用所在的线程，而蓝牙mcu子系统从这个循环buffer队列中读（对应函数：AudDrv_BTCVSD_WriteToBT）则是在中断线程中，所以他们也存在同步和竞争的关系。驱动通过如下成员来控制

• 自旋锁：auddrv_BTCVSDTX_lock
• 等待队列：BTCVSD_Write_Wait_Queue/BTCVSD_write_wait_queue_flag

同样由于是在中断中，所以必须使用spin_lock_irqsave、spin_unlock_irqrestore形式来锁住和释放该自旋锁。

3 sco的接收流程

如下为read系统调用涉及的模块的数据流图，注意从receive package address register读出的地址只是一个偏移量，需要加上物理内存的开始地址对应的虚拟地址。

read的调用流程如下：

AudDrv_btcvsd_read
|------>read_size:(btsco.pRX->iPacket_w - btsco.pRX->iPacket_r) * (SCO_RX_PLC_SIZE + BTSCO_CVSD_PACKET_VALID_SIZE);
|------>BTSCORX_ReadIdx_tmp:(btsco.pRX->iPacket_r & SCO_RX_PACKET_MASK) * (SCO_RX_PLC_SIZE + BTSCO_CVSD_PACKET_VALID_SIZE);
|------>copy_to_user((void __user *)Read_Data_Ptr, (void *)((kal_uint8 *)btsco.pRX->PacketBuf + BTSCORX_ReadIdx_tmp), read_size)
|--->wait_event_interruptible_timeout(BTCVSD_Read_Wait_Queue, BTCVSD_read_wait_queue_flag...) // if have not enough data available to read，then sleep on wait queue

中断处理中对应的read 系统调用对应的循环buffer的处理

AudDrv_BTCVSD_IRQ_handler
|---->uControl = *bt_hw_REG_CONTROL;
|----> uPacketType = (uControl >> 18) & 0x7;
|----> uPacketLength = (kal_uint32)btsco_PacketInfo[uPacketType][0];
|---->uPacketNumber = (kal_uint32)btsco_PacketInfo[uPacketType][1];
|---->uBufferCount_TX = (kal_uint32)btsco_PacketInfo[uPacketType][2];
|---->uBufferCount_RX = (kal_uint32)btsco_PacketInfo[uPacketType][3];
|---->AudDrv_BTCVSD_ReadFromBT(uPacketType, uPacketLength, uPacketNumber, uBufferCount_RX, uControl);
       |------>connsys_addr_rx = *bt_hw_REG_PACKET_R;
       |------>ap_addr_rx = (kal_uint32)BTSYS_SRAM_BANK2_BASE_ADDRESS + (connsys_addr_rx & 0xFFFF);
       |------>AudDrv_BTCVSD_DataTransfer(BT_SCO_DIRECT_BT2ARM, pSrc, btsco.pRX->TempPacketBuf, uPacketLength, uPacketNumber, btsco.uRXState);
       |------>memcpy(btsco.pRX->PacketBuf[btsco.pRX->iPacket_w & SCO_RX_PACKET_MASK], btsco.pRX->TempPacketBuf + (SCO_RX_PLC_SIZE * i), SCO_RX_PLC_SIZE);
       |------>btsco.pRX->iPacket_w++;
|---->*bt_hw_REG_CONTROL &= ~BT_CVSD_CLEAR;
|---->BTCVSD_read_wait_queue_flag = 1;
|---->wake_up_interruptible(&BTCVSD_Read_Wait_Queue);//alread received data from BT chip, so wake up read system call function to fetch data

4 sco的发送流程

write的调用流程如下：

AudDrv_btcvsd_write
|------>copy_size = btsco.pTX->u4BufferSize - (btsco.pTX->iPacket_w - btsco.pTX->iPacket_r) * SCO_TX_ENCODE_SIZE; //  free space of TX packet buffer
|------>BTSCOTX_WriteIdx = (btsco.pTX->iPacket_w & SCO_TX_PACKET_MASK) * SCO_TX_ENCODE_SIZE;
|------>copy_from_user((void *)((kal_uint8 *)btsco.pTX->PacketBuf + BTSCOTX_WriteIdx), (const void __user *)data_w_ptr, copy_size)
|------>btsco.pTX->iPacket_w += copy_size / SCO_TX_ENCODE_SIZE;
|------>BTCVSD_write_wait_queue_flag = 0;
|------>wait_event_interruptible_timeout(BTCVSD_Write_Wait_Queue, BTCVSD_write_wait_queue_flag, ...)//if have not enough space available to write,then sleep on wait queue

中断处理中对应的write系统调用对应的循环buffer的处理

AudDrv_BTCVSD_IRQ_handler
|---->uControl = *bt_hw_REG_CONTROL;
|---->uPacketType = (uControl >> 18) & 0x7;
|---->uPacketLength = (kal_uint32)btsco_PacketInfo[uPacketType][0];
|---->uPacketNumber = (kal_uint32)btsco_PacketInfo[uPacketType][1];
|---->uBufferCount_TX = (kal_uint32)btsco_PacketInfo[uPacketType][2];
|---->uBufferCount_RX = (kal_uint32)btsco_PacketInfo[uPacketType][3];
|---->AudDrv_BTCVSD_WriteToBT
         |--->memcpy((void *)(btsco.pTX->TempPacketBuf + (SCO_TX_ENCODE_SIZE * i)), (void *)(btsco.pTX->PacketBuf[btsco.pTX->iPacket_r & SCO_TX_PACKET_MASK]), SCO_TX_ENCODE_SIZE);
         |--->btsco.pTX->iPacket_r++;
         |--->connsys_addr_tx = *bt_hw_REG_PACKET_W;
         |--->pDst= (kal_uint32)BTSYS_SRAM_BANK2_BASE_ADDRESS + (connsys_addr_tx & 0xFFFF);
         |--->AudDrv_BTCVSD_DataTransfer(BT_SCO_DIRECT_ARM2BT, btsco.pTX->TempPacketBuf, pDst, uPacketLength, uPacketNumber, btsco.uTXState);
|----> *bt_hw_REG_CONTROL &= ~BT_CVSD_CLEAR;
|---->BTCVSD_write_wait_queue_flag = 1;
|---->wake_up_interruptible(&BTCVSD_Write_Wait_Queue);//already have free space for write syscall, so wake up write system call to fill data