VxWorks BSP学习笔记_串口驱动

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VxWorks BSP学习笔记（基于SBC8349E）

1. 串口驱动

1.1 串行驱动程序的重要结构

以下结构指出了驱动程序函数的入口点 ../target/h/sioLib.h

Typedef struct sio_drv_funcs /* driver functions */

{

int (*ioctl)

(

SIO_CHAN * pSioChan,

int cmd,

void * arg

);

int (*txStartup)

(

SIO_CHAN * pSioChan

);

int (*callbackInstall)

(

SIO_CHAN * pSioChan,

int callbackType,

STATUS (*callback)(void *, ...),

void * callbackArg

);

int (*pollInput)

(

SIO_CHAN * pSioChan,

char * inChar

);

int (*pollOutput)

(

SIO_CHAN * pSioChan,

char outChar

);

}SIO_DRV_FUNCS;

typedef struct sio_chan /* a serial channel */

{

SIO_DRV_FUNCS * pDrvFuncs;

/* device data */

} SIO_CHAN;

在串行设备的驱动程序中，必须有一个包含指向SIO_DRV_FUNCS指针的结构（XX_CHAN）,这个结构可以包含设备的其他信息以及提供给高层协议的回调函数。以16550为例：

../target/h/drv/sio/ns16552Sio.h

typedef struct /* NS16550_CHAN * */

{

/* always goes first */

SIO_DRV_FUNCS * pDrvFuncs; /* driver functions */

/* callbacks */

STATUS (*getTxChar) (); /* pointer to xmitr function */

STATUS (*putRcvChar) (); /* pointer to rcvr function */

void * getTxArg;

void * putRcvArg;

UINT8 *regs; /* NS16552 registers */

UINT8 level; /* 8259a interrupt level for this device */

UINT8 ier; /* copy of ier */

UINT8 lcr; /* copy of lcr, not used by ns16552 driver */

UINT8 mcr; /* copy of modem control register */

UINT16 channelMode; /* such as INT, POLL modes */

UINT16 regDelta; /* register address spacing */

int baudRate;

UINT32 xtal; /* UART clock frequency */

UINT32 options; /* hardware setup options */

} NS16550_CHAN;

1.2 串行驱动程序的初始化函数

串行设备驱动程序的初始化函数应该包含下面的内容：

1）包含一个指向xx_DRV结构的指针；

2）初始化xx_CHAN；

3）初始化驱动程序必要的内容；

4）重新设置芯片

../target/src/drv/sio/ns16550Sio.c

/* driver functions */

#ifdef INCLUDE_TTY_DEV

static SIO_DRV_FUNCS ns16550SioDrvFuncs =

{

(int (*)()) ns16550Ioctl,

(int (*)()) ns16550TxStartup,

(int (*)()) ns16550CallbackInstall,

(int (*)()) ns16550PollInput,

(int (*)(SIO_CHAN *,char))ns16550PollOutput

};

#else /* INCLUDE_TTY_DEV */

static SIO_DRV_FUNCS ns16550SioDrvFuncs =

{

(int (*)()) NULL,

(int (*)()) ns16550PollInput,

(int (*)(SIO_CHAN *,char))ns16550PollOutput

};

#endif /* INCLUDE_TTY_DEV */

void ns16550DevInit

(

NS16550_CHAN * pChan /* pointer to channel */

)

{

int oldlevel = intLock ();

/* initialize the driver function pointers in the SIO_CHAN's */

pChan->pDrvFuncs = &ns16550SioDrvFuncs;

/* set the non BSP-specific constants */

pChan->getTxChar = ns16550DummyCallback;

pChan->putRcvChar = ns16550DummyCallback;

pChan->channelMode = 0; /* undefined */

pChan->options = (CLOCAL | CREAD | CS8);

pChan->mcr = MCR_OUT2;

/* reset the chip */

ns16550InitChannel (pChan);

intUnlock (oldlevel);

}

1.3 回调安装函数以及驱动各函数的实现

SIO_DRV_FUNCS结构中的各函数的实现

1.4 串行设备的安装

1.4.1 串行设备的初始化

sysDuartHwInit()，由usrInit()函数调用，初始化了驱动程序相关的xx_CHAN结构。调用了xxDevInit()函数初始化硬件，设置中断未连接标志。该函数在内核初始化之前完成。使用16550芯片的例子：

void sysDuartHwInit (void)

{

int i;

eumbbar_base = (char *)CCSBAR;

for (i = 0; i < N_DUART_CHANNELS; i++)

{

ns16550Chan[i].regs = (UINT8 *)devDuartParas[i].baseAdrs;

ns16550Chan[i].level = devDuartParas[i].intLevel;

ns16550Chan[i].channelMode = SIO_MODE_INT;

ns16550Chan[i].regDelta = devDuartParas[i].regSpace;

ns16550Chan[i].baudRate = DUART_BAUD;

ns16550Chan[i].xtal = sysClkFreqGet();

ns16550DevInit (&ns16550Chan[i]);

}

/* 以下初始硬件 */

if (ns16550Chan[0].channelMode == SIO_MODE_INT)

{

eumbbar_base[UDCR1] = 0x01; /* set duart mode */

eumbbar_base[ULCR1] = 0x80; /* open DLAB */

eumbbar_base[UAFR1] = 0x00;

eumbbar_base[UDMB1] = 0x03; /* for mpc8245 MSB, 9600bps @66Mhz */

eumbbar_base[UDLB1] = 0x64; /* LSB */

eumbbar_base[ULCR1] = 0x03; /* clear DLAB, no-parity, 1stop bit, 8bit data */

eumbbar_base[UMCR1] = 0x02; /* disable loopback mode */

eumbbar_base[UIER1] = 0x03; /* Tx empty, Rx interrupt enable */

}

if (ns16550Chan[1].channelMode == SIO_MODE_INT)

{

eumbbar_base[UDCR2] = 0x01; /* set duart mode */

eumbbar_base[ULCR2] = 0x80; /* open DLAB */

eumbbar_base[UAFR2] = 0x00;

eumbbar_base[UDMB2] = 0x01; /* for mpc8245 MSB, 9600bps @66Mhz */

eumbbar_base[UDLB2] = 0xB2; /* LSB */

eumbbar_base[ULCR2] = 0x03; /* clear DLAB, no-parity, 1stop bit, 8bit data */

eumbbar_base[UMCR2] = 0x02; /* diable loopback mode */

eumbbar_base[UIER2] = 0x03; /* Tx empty, Rx interrupt enable */

}

} /* sysDuartHwInit () */

1.4.2 安装串行设备的ISR

sysDuartHwInit2()由usrRoot任务中的sysClkConnnect()函数调用，安装了设备的中断服务程序。这个函数在系统初始化之后执行，此时系统已经可以执行中断连接了。

void sysSerialHwInit2 (void)

{

int i;

/* connect serial interrupts */

for (i = 0; i < N_DUART_CHANNELS; i++)

{

(void) intConnect ((VOIDFUNCPTR *)((int)devDuartParas[i].vector),

(VOIDFUNCPTR)ns16550Int, (int)&ns16550Chan[i] );

intEnable (devDuartParas[i].vector);

}

} /* sysDuartHwInit2 () */

1.4.3 串行设备描述符与通道号的转换

sysSerialChanGet()的作用是将串行设备通道的索引转换为该通道的设备描述符。通常目标机代理会使用这个函数以获得通道的指针，usrRoot()任务也会用到该函数。

SIO_CHAN * sysSerialChanGet

(

int channel /* serial channel */

)

{

if ( (channel < 0) ||

(channel >= (int)NELEMENTS(sysSerialSioChans)) )

return (SIO_CHAN *) ERROR;

return sysSerialSioChans[channel];

}