FreeCalypso > hg > freecalypso-sw
annotate target-utils/libcommon/cmd_baud_switch.c @ 865:f5affe83ba2d
lldbg hack (poor girl's substitute for JTAG) implemented
author | Space Falcon <falcon@ivan.Harhan.ORG> |
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date | Fri, 15 May 2015 00:02:03 +0000 |
parents | 437f9365249c |
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1 /* |
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2 * Baud rate switching command |
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3 */ |
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4 |
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5 #include <stdlib.h> |
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6 #include "types.h" |
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7 #include "ns16550.h" |
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8 |
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9 extern struct ns16550_regs *uart_base; |
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10 extern int serial_in_poll(); |
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11 |
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12 static const struct tab { |
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13 int baud; |
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14 int divisor; |
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15 } rate_table[] = { |
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16 /* |
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17 * First support the rates and divisors implemented by the |
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18 * Calypso boot ROM. Dividing 13 MHz by 7 gives an approximation |
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19 * of 115200 (x16); the divisors used by the boot ROM code for |
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20 * the slower baud rates are all 7x the usual PC value. |
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21 */ |
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22 {115200, 7}, |
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23 {57600, 7 * 2}, |
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24 {38400, 7 * 3}, |
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25 {28800, 7 * 4}, |
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26 {19200, 7 * 6}, |
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27 /* |
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28 * Going faster than ~115200 baud means using a divisor |
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29 * less than 7, resulting in a non-standard baud rate. |
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30 * The /1, /2 and /4 seem like reasonable choices. |
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31 */ |
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32 {812500, 1}, |
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33 {406250, 2}, |
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34 {203125, 4}, |
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35 /* that's all we really need to support */ |
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36 {0, 0} |
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37 }; |
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38 |
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39 /* |
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40 * The following helper function actually switches the UART |
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41 * baud rate divisor. Call serial_flush() first. It returns the |
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42 * old divisor value. |
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43 * |
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44 * Note the u8 type for both the new and old divisor values. |
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45 * All supported divisors are well below 255, so we don't bother |
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46 * with the upper byte. |
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47 */ |
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48 static u8 |
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49 actually_switch_baud(newdiv) |
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50 u8 newdiv; |
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51 { |
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52 volatile struct ns16550_regs *regs; |
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53 u8 save_lcr, save_old_baud; |
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54 |
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55 regs = uart_base; |
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56 save_lcr = regs->lcr; |
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57 regs->lcr = save_lcr | NS16550_LCR_DLAB; |
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58 save_old_baud = regs->datareg; |
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59 regs->datareg = newdiv; |
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60 regs->lcr = save_lcr; |
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61 return(save_old_baud); |
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62 } |
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63 |
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64 void |
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65 cmd_baud_switch(argbulk) |
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66 char *argbulk; |
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67 { |
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68 char *argv[2]; |
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69 int baudarg; |
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70 struct tab *tp; |
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71 u8 save_old_baud; |
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72 int c; |
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73 |
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74 if (parse_args(argbulk, 1, 1, argv, 0) < 0) |
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75 return; |
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76 baudarg = atoi(argv[0]); |
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77 for (tp = rate_table; tp->baud; tp++) |
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78 if (tp->baud == baudarg) |
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79 break; |
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80 if (!tp->baud) { |
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81 printf("ERROR: invalid/unimplemented baud rate argument\n"); |
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82 return; |
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83 } |
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84 |
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85 /* do it */ |
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86 serial_flush(); |
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87 save_old_baud = actually_switch_baud(tp->divisor); |
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88 |
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89 /* |
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90 * After getting the echo of this command at the old baud rate |
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91 * (see the serial flush call just before switching the divisor), |
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92 * the line will go silent from the user's perspective. |
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93 * The user should wait just a little bit, then send us a 0x55 ('U') |
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94 * at the new baud rate - we should be in the below loop waiting |
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95 * for this character by then. Receiving that character |
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96 * correctly (0x55 was chosen for the bit pattern - unlikely to |
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97 * be received if the sender is sending at a wrong baud rate) |
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98 * will cause us to conclude this command and return a new '=' |
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99 * prompt at the new baud rate. |
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100 * |
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101 * If we get something else, we assume that someone messed up, |
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102 * switch back to the old baud rate, scribble an error message |
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103 * and return. |
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104 */ |
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105 do |
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106 c = serial_in_poll(); |
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107 while (c < 0); |
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108 if (c != 0x55) { |
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109 actually_switch_baud(save_old_baud); |
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110 printf("ERROR: no \'U\' received, switched back to old baud rate\n"); |
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111 } |
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112 } |