arch/powerpc/kernel/udbg_16550.c

   1 /*
   2  * udbg for for NS16550 compatable serial ports
   3  *
   4  * Copyright (C) 2001-2005 PPC 64 Team, IBM Corp
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11 #include <linux/types.h>
  12 #include <asm/udbg.h>
  13 #include <asm/io.h>
  14
  15 extern u8 real_readb(volatile u8 __iomem  *addr);
  16 extern void real_writeb(u8 data, volatile u8 __iomem *addr);
  17
  18 struct NS16550 {
  19         /* this struct must be packed */
  20         unsigned char rbr;  /* 0 */
  21         unsigned char ier;  /* 1 */
  22         unsigned char fcr;  /* 2 */
  23         unsigned char lcr;  /* 3 */
  24         unsigned char mcr;  /* 4 */
  25         unsigned char lsr;  /* 5 */
  26         unsigned char msr;  /* 6 */
  27         unsigned char scr;  /* 7 */
  28 };
  29
  30 #define thr rbr
  31 #define iir fcr
  32 #define dll rbr
  33 #define dlm ier
  34 #define dlab lcr
  35
  36 #define LSR_DR   0x01  /* Data ready */
  37 #define LSR_OE   0x02  /* Overrun */
  38 #define LSR_PE   0x04  /* Parity error */
  39 #define LSR_FE   0x08  /* Framing error */
  40 #define LSR_BI   0x10  /* Break */
  41 #define LSR_THRE 0x20  /* Xmit holding register empty */
  42 #define LSR_TEMT 0x40  /* Xmitter empty */
  43 #define LSR_ERR  0x80  /* Error */
  44
  45 #define LCR_DLAB 0x80
  46
  47 static volatile struct NS16550 __iomem *udbg_comport;
  48
  49 static void udbg_550_putc(char c)
  50 {
  51         if (udbg_comport) {
  52                 while ((in_8(&udbg_comport->lsr) & LSR_THRE) == 0)
  53                         /* wait for idle */;
  54                 out_8(&udbg_comport->thr, c);
  55                 if (c == '\n')
  56                         udbg_550_putc('\r');
  57         }
  58 }
  59
  60 static int udbg_550_getc_poll(void)
  61 {
  62         if (udbg_comport) {
  63                 if ((in_8(&udbg_comport->lsr) & LSR_DR) != 0)
  64                         return in_8(&udbg_comport->rbr);
  65                 else
  66                         return -1;
  67         }
  68         return -1;
  69 }
  70
  71 static int udbg_550_getc(void)
  72 {
  73         if (udbg_comport) {
  74                 while ((in_8(&udbg_comport->lsr) & LSR_DR) == 0)
  75                         /* wait for char */;
  76                 return in_8(&udbg_comport->rbr);
  77         }
  78         return -1;
  79 }
  80
  81 void udbg_init_uart(void __iomem *comport, unsigned int speed,
  82                     unsigned int clock)
  83 {
  84         unsigned int dll, base_bauds;
  85
  86         if (clock == 0)
  87                 clock = 1843200;
  88         if (speed == 0)
  89                 speed = 9600;
  90
  91         base_bauds = clock / 16;
  92         dll = base_bauds / speed;
  93
  94         if (comport) {
  95                 udbg_comport = (struct NS16550 __iomem *)comport;
  96                 out_8(&udbg_comport->lcr, 0x00);
  97                 out_8(&udbg_comport->ier, 0xff);
  98                 out_8(&udbg_comport->ier, 0x00);
  99                 out_8(&udbg_comport->lcr, LCR_DLAB);
 100                 out_8(&udbg_comport->dll, dll & 0xff);
 101                 out_8(&udbg_comport->dlm, dll >> 8);
 102                 /* 8 data, 1 stop, no parity */
 103                 out_8(&udbg_comport->lcr, 0x03);
 104                 /* RTS/DTR */
 105                 out_8(&udbg_comport->mcr, 0x03);
 106                 /* Clear & enable FIFOs */
 107                 out_8(&udbg_comport->fcr ,0x07);
 108                 udbg_putc = udbg_550_putc;
 109                 udbg_getc = udbg_550_getc;
 110                 udbg_getc_poll = udbg_550_getc_poll;
 111         }
 112 }
 113
 114 unsigned int udbg_probe_uart_speed(void __iomem *comport, unsigned int clock)
 115 {
 116         unsigned int dll, dlm, divisor, prescaler, speed;
 117         u8 old_lcr;
 118         volatile struct NS16550 __iomem *port = comport;
 119
 120         old_lcr = in_8(&port->lcr);
 121
 122         /* select divisor latch registers.  */
 123         out_8(&port->lcr, LCR_DLAB);
 124
 125         /* now, read the divisor */
 126         dll = in_8(&port->dll);
 127         dlm = in_8(&port->dlm);
 128         divisor = dlm << 8 | dll;
 129
 130         /* check prescaling */
 131         if (in_8(&port->mcr) & 0x80)
 132                 prescaler = 4;
 133         else
 134                 prescaler = 1;
 135
 136         /* restore the LCR */
 137         out_8(&port->lcr, old_lcr);
 138
 139         /* calculate speed */
 140         speed = (clock / prescaler) / (divisor * 16);
 141
 142         /* sanity check */
 143         if (speed < 0 || speed > (clock / 16))
 144                 speed = 9600;
 145
 146         return speed;
 147 }
 148
 149 #ifdef CONFIG_PPC_MAPLE
 150 void udbg_maple_real_putc(char c)
 151 {
 152         if (udbg_comport) {
 153                 while ((real_readb(&udbg_comport->lsr) & LSR_THRE) == 0)
 154                         /* wait for idle */;
 155                 real_writeb(c, &udbg_comport->thr); eieio();
 156                 if (c == '\n')
 157                         udbg_maple_real_putc('\r');
 158         }
 159 }
 160
 161 void __init udbg_init_maple_realmode(void)
 162 {
 163         udbg_comport = (volatile struct NS16550 __iomem *)0xf40003f8;
 164
 165         udbg_putc = udbg_maple_real_putc;
 166         udbg_getc = NULL;
 167         udbg_getc_poll = NULL;
 168 }
 169 #endif /* CONFIG_PPC_MAPLE */