学步园

其实到这里，只要能保证编译通过，再修改一下链接脚本，其实已经可以跑在at9260的系统上了。因为我没有仿真器，不知道程序的状态，所以必须撰写调试串口的驱动。

RTEMS 的调试串口并没有采用中断输出的方式，而是采用查询输出的方式。相对来说比较容易。

RTEMS里有两个打印函数：

printf 和 printk

printf是由库支持的打印函数，内部比较复杂，主要用于应用程序级别的打印，不能用于内核和中断的打印，特别是中断中不能使用该函数，否则会引起死机。

printk是由rtems的调试打印函数，主要用于内核和中断的打印。任务级别也可以调用，但是最好不要这样做。

printk是调用 BSP_output_char 这个函数指针完成字符的输出。

可以在c/src/lib/lbicpu/arm/at91sam9260/dbgu/Dbgu.c中的末尾的

static void _BSP_put_char( char c ) {
    dbgu_write_polled(0, c);
}

BSP_output_char_function_type BSP_output_char = _BSP_put_char;

那么就是说，printk实际上是调用调试串口驱动完成字符的输出。

既然调用调试串口输出，必须等调试串口初始化完成以后才能输出。

start.S执行完毕后，是跳转到 bootcard 函数中继续执行，bootcard 要完成对内核数据的初始化后，才调用IO的初始化，这时串口的驱动才能工作。也就是说，想在bootcard运行调试串口初始化以前，看到printk的输出，基本上是不可能的。

如果你真的想这个时候也能看到printk的输出，只能提前初始化串口驱动了。

我的做法是，dbgu_write 函数内部会检查调试串口有没有被初始化，如果没有被初始化，先初始化再输出字符。那么这样，即使在start.S汇编文件里调用printk，也是能看到输出的。

这里还要注意一个问题就是调试串口的波特率，调试串口的波特率是通过函数BSP_get_baud获得，

这个函数在c/src/lib/libbsp/arm/at9260/include/bsp.h中。

另外就是修改 c/src/lib/libbsp/arm/at9260/console/uarts.c的代码。

这里的改动主要是一些配置和寄存器，没有什么好讲的。

下面是dbgu.c的源代码：

/*<br /> * Console driver for AT91SAM9260 DBGU port<br /> *<br /> */<br /> #include <bsp.h><br /> #include <rtems/libio.h><br /> #include <termios.h><br /> #include <at91sam9260.h><br /> #include <rtems/bspIo.h><br /> #include <libchip/serial.h><br /> #include <libchip/sersupp.h></p> <p>#define AT91SAM9260_DBGU_NUM 1<br /> static volatile int _gIsInitDbgu[AT91SAM9260_DBGU_NUM] = {0};<br /> volatile int dbg_dly;<br /> /* static function prototypes */<br /> static int dbgu_first_open(int major, int minor, void *arg);<br /> static int dbgu_last_close(int major, int minor, void *arg);<br /> static int dbgu_read(int minor);<br /> static int dbgu_write(int minor, const char *buf, int len);<br /> static void dbgu_init(int minor);<br /> static void dbgu_write_polled(int minor, char c);<br /> static int dbgu_set_attributes(int minor, const struct termios *t);<br /> /* Pointers to functions for handling the UART. */<br /> console_fns dbgu_fns =<br /> {<br /> libchip_serial_default_probe,<br /> dbgu_first_open,<br /> dbgu_last_close,<br /> dbgu_read,<br /> dbgu_write,<br /> dbgu_init,<br /> dbgu_write_polled, /* not used in this driver */<br /> dbgu_set_attributes,<br /> FALSE /* TRUE if interrupt driven, FALSE if not. */<br /> };<br /> /*********************************************************************/<br /> /* Functions called via callbacks (i.e. the ones in uart_fns */<br /> /*********************************************************************/<br /> /*<br /> * This is called the first time each device is opened. Since<br /> * the driver is polled, we don't have to do anything. If the driver<br /> * were interrupt driven, we'd enable interrupts here.<br /> */<br /> static int dbgu_first_open(int major, int minor, void *arg)<br /> {<br /> return 0;<br /> }</p> <p>/*<br /> * This is called the last time each device is closed. Since<br /> * the driver is polled, we don't have to do anything. If the driver<br /> * were interrupt driven, we'd disable interrupts here.<br /> */<br /> static int dbgu_last_close(int major, int minor, void *arg)<br /> {<br /> return 0;<br /> }</p> <p>/*<br /> * Read one character from UART.<br /> *<br /> * return -1 if there's no data, otherwise return<br /> * the character in lowest 8 bits of returned int.<br /> */<br /> static int dbgu_read(int minor)<br /> {<br /> char c;<br /> console_tbl *console_entry;<br /> AT91S_DBGU *dbgu;<br /> if ((minor < AT91SAM9260_DBGU_NUM) && (0 == _gIsInitDbgu[minor]))<br /> dbgu_init(minor);</p> <p> console_entry = BSP_get_uart_from_minor(minor);<br /> if (console_entry == NULL) {<br /> return -1;<br /> }<br /> dbgu = (AT91S_DBGU *)console_entry->ulCtrlPort1;<br /> if (!(dbgu->DBGU_CSR & AT91C_US_RXRDY)) {<br /> return -1;<br /> }</p> <p> c = dbgu->DBGU_RHR & 0xff; </p> <p> return c;<br /> }</p> <p>/*<br /> * Write buffer to UART<br /> *<br /> * return 1 on success, -1 on error<br /> */<br /> static int dbgu_write(int minor, const char *buf, int len)<br /> {<br /> int i, x;<br /> char c;<br /> console_tbl *console_entry;<br /> AT91S_DBGU *dbgu;</p> <p> if ((minor < AT91SAM9260_DBGU_NUM) && (0 == _gIsInitDbgu[minor]))<br /> dbgu_init(minor);</p> <p> console_entry = BSP_get_uart_from_minor(minor);<br /> if (console_entry == NULL) {<br /> return -1;<br /> }<br /> dbgu = (AT91S_DBGU *)console_entry->ulCtrlPort1;<br /> for (i = 0; i < len; i++) {<br /> /* Wait for fifo to have room */<br /> while(1) {<br /> if (dbgu->DBGU_CSR & AT91C_US_TXRDY) {<br /> break;<br /> }<br /> }</p> <p> c = (char) buf[i];<br /> dbgu->DBGU_THR = c;</p> <p> /* the TXRDY flag does not seem to update right away (is this true?) */<br /> /* so we wait a bit before continuing */<br /> for (x = 0; x < 10; x++) {<br /> dbg_dly++; /* using a global so this doesn't get optimized out */<br /> }<br /> }</p> <p> return 1;<br /> }</p> <p>/* Set up the UART. */<br /> static void dbgu_init(int minor)<br /> {<br /> console_tbl *console_entry;<br /> AT91S_DBGU *dbgu;</p> <p> if ((minor >= AT91SAM9260_DBGU_NUM) || (_gIsInitDbgu[minor] > 0))<br /> return ;</p> <p> console_entry = BSP_get_uart_from_minor(minor);<br /> if (console_entry == NULL) {<br /> return;<br /> }<br /> _gIsInitDbgu[minor] = 1;</p> <p> dbgu = (AT91S_DBGU *)console_entry->ulCtrlPort1;<br /> AT91C_BASE_PIOB->PIO_IDR = (1<<14) | (1<<15);<br /> AT91C_BASE_PIOB->PIO_ASR = (1<<14) | (1<<15);<br /> AT91C_BASE_PIOB->PIO_BSR = 0;<br /> AT91C_BASE_PIOB->PIO_PDR = (1<<14) | (1<<15);<br /> AT91C_BASE_PIOB->PIO_PPUDR = (1<<14) | (1<<15);</p> <p> /* Clear error bits, and reset */<br /> dbgu->DBGU_CR = (AT91C_US_RSTSTA | AT91C_US_RSTTX | AT91C_US_RSTRX);<br /> /* Clear pending interrupts */<br /> dbgu->DBGU_IDR = (AT91C_US_RXRDY | AT91C_US_TXRDY | AT91C_US_ENDRX |<br /> AT91C_US_ENDTX | AT91C_US_OVRE | AT91C_US_FRAME |<br /> AT91C_US_PARE | AT91C_US_TXEMPTY | AT91C_US_TXBUFE |<br /> AT91C_US_RXBUFF | AT91C_US_COMM_TX | AT91C_US_COMM_RX);<br /> dbgu->DBGU_IMR = 0;<br /> /* Set port to no parity, no loopback */<br /> dbgu->DBGU_MR = AT91C_US_PAR_NONE | AT91C_US_CHMODE_NORMAL;<br /> /* Set the baud rate */<br /> dbgu->DBGU_BRGR = (at91sam9260_get_mck() / 16) / BSP_get_baud();<br /> /* Enable the DBGU */<br /> dbgu->DBGU_CR = (AT91C_US_RXEN | AT91C_US_TXEN);<br /> }<br /> /* I'm not sure this is needed for the shared console driver. */<br /> static void dbgu_write_polled(int minor, char c)<br /> {<br /> dbgu_write(minor, &c, 1);<br /> }<br /> /* This is for setting baud rate, bits, etc. */<br /> static int dbgu_set_attributes(int minor, const struct termios *t)<br /> {<br /> return 0;<br /> }<br /> /***********************************************************************/<br /> /*<br /> * The following functions are not used by TERMIOS, but other RTEMS<br /> * functions use them instead.<br /> */<br /> /***********************************************************************/<br /> /*<br /> * Read from UART. This is used in the exit code, and can't<br /> * rely on interrupts.<br /> */<br /> int dbgu_poll_read(int minor)<br /> {<br /> return dbgu_read(minor);<br /> }</p> <p>/*<br /> * Write a character to the console. This is used by printk() and<br /> * maybe other low level functions. It should not use interrupts or any<br /> * RTEMS system calls. It needs to be very simple<br /> */<br /> static void _BSP_put_char( char c ) {<br /> dbgu_write_polled(0, c);<br /> }<br /> BSP_output_char_function_type BSP_output_char = _BSP_put_char;<br />

下面是uarts.c的代码：

/*<br /> * Console driver for AT9260<br /> *<br /> * This driver uses the shared console driver in<br /> * ...../libbsp/shared/console.c<br /> *<br /> */<br /> #include <bsp.h><br /> #include <rtems/libio.h><br /> #include <termios.h><br /> #include <rtems/bspIo.h><br /> #include <at91sam9260.h><br /> #include <libchip/serial.h><br /> #include <libchip/sersupp.h><br /> /* How many serial ports? */<br /> #define NUM_DEVS 1<br /> /* These are used by code in console.c */<br /> unsigned long Console_Port_Count = NUM_DEVS;<br /> console_data Console_Port_Data[NUM_DEVS];<br /> /* rtems console uses the following minor number */<br /> rtems_device_minor_number Console_Port_Minor = 0;<br /> extern console_fns dbgu_fns;<br /> /*<br /> * There's one item in array for each UART.<br /> *<br /> * Some of these fields are marked "NOT USED". They are not used<br /> * by console.c, but may be used by drivers in libchip<br /> *<br /> * when we add other types of UARTS we will need to move this<br /> * structure to a generic uart.c file with only this in it<br /> */<br /> console_tbl Console_Port_Tbl[] = {<br /> {<br /> "/dev/console", /* sDeviceName */<br /> SERIAL_CUSTOM, /* deviceType */<br /> &dbgu_fns, /* pDeviceFns */<br /> NULL, /* deviceProbe */<br /> NULL, /* pDeviceFlow */<br /> 0, /* ulMargin - NOT USED */<br /> 0, /* ulHysteresis - NOT USED */<br /> NULL, /* pDeviceParams */<br /> AT91C_BASE_DBGU, /* ulCtrlPort1 - Pointer to DBGU regs */<br /> 0, /* ulCtrlPort2 - NOT USED */<br /> 0, /* ulDataPort - NOT USED */<br /> NULL, /* getRegister - NOT USED */<br /> NULL, /* setRegister - NOT USED */<br /> NULL, /* getData - NOT USED */<br /> NULL, /* setData - NOT USED */<br /> 0, /* ulClock - NOT USED */<br /> 0 /* ulIntVector - NOT USED */<br /> }};</p> <p>console_tbl *BSP_get_uart_from_minor(int minor)<br /> {<br /> return &Console_Port_Tbl[minor];<br /> } 

至此，搞定调试串口驱动。