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1 // driver for ARM PrimeCell UART (PL011)
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2 #include "types.h"
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3 #include "defs.h"
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4 #include "param.h"
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5 #include "arm.h"
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6 #include "memlayout.h"
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7
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8 static volatile uint *uart_base;
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9 void isr_uart (struct trapframe *tf, int idx);
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10
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11 #define UART_DR 0 // data register
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12 #define UART_RSR 1 // receive status register/error clear register
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13 #define UART_FR 6 // flag register
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14 #define UART_IBRD 9 // integer baud rate register
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15 #define UART_FBRD 10 // Fractional baud rate register
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16 #define UART_LCR 11 // line control register
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17 #define UART_CR 12 // control register
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18 #define UART_IMSC 14 // interrupt mask set/clear register
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19 #define UART_MIS 16 // masked interrupt status register
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20 #define UART_ICR 17 // interrupt clear register
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21 // bits in registers
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22 #define UARTFR_TXFF (1 << 5) // tramit FIFO full
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23 #define UARTFR_RXFE (1 << 4) // receive FIFO empty
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24 #define UARTCR_RXE (1 << 9) // enable receive
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25 #define UARTCR_TXE (1 << 8) // enable transmit
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26 #define UARTCR_EN (1 << 0) // enable UART
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27 #define UARTLCR_FEN (1 << 4) // enable FIFO
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28 #define UART_RXI (1 << 4) // receive interrupt
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29 #define UART_TXI (1 << 5) // transmit interrupt
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30 #define UART_BITRATE 19200
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31
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32 // enable uart
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33 void uart_init (void *addr)
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34 {
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35 uint left;
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36
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37 uart_base = addr;
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38
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39 // set the bit rate: integer/fractional baud rate registers
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40 uart_base[UART_IBRD] = UART_CLK / (16 * UART_BITRATE);
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41
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42 left = UART_CLK % (16 * UART_BITRATE);
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43 uart_base[UART_FBRD] = (left * 4 + UART_BITRATE / 2) / UART_BITRATE;
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44
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45 // enable trasmit and receive
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46 uart_base[UART_CR] |= (UARTCR_EN | UARTCR_RXE | UARTCR_TXE);
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47
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48 // enable FIFO
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49 uart_base[UART_LCR] |= UARTLCR_FEN;
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50 }
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51
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52 // enable the receive (interrupt) for uart (after PIC has initialized)
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53 void uart_enable_rx ()
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54 {
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55 uart_base[UART_IMSC] = UART_RXI;
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56 pic_enable(PIC_UART0, isr_uart);
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57 }
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58
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59 void uartputc (int c)
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60 {
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61 // wait a short period if the transmit FIFO is full
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62 while (uart_base[UART_FR] & UARTFR_TXFF) {
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63 micro_delay(10);
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64 }
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65
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66 uart_base[UART_DR] = c;
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67 }
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68
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69 //poll the UART for data
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70 int uartgetc (void)
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71 {
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72 if (uart_base[UART_FR] & UARTFR_RXFE) {
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73 return -1;
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74 }
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75
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76 return uart_base[UART_DR];
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77 }
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78
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79 void isr_uart (struct trapframe *tf, int idx)
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80 {
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81 if (uart_base[UART_MIS] & UART_RXI) {
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82 consoleintr(uartgetc);
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83 }
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84
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85 // clear the interrupt
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86 uart_base[UART_ICR] = UART_RXI | UART_TXI;
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87 }
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