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/config.h>
  12 #include <linux/types.h>
  13 #include <asm/udbg.h>
  14 #include <asm/io.h>
  15
  16 extern u8 real_readb(volatile u8 __iomem  *addr);
  17 extern void real_writeb(u8 data, volatile u8 __iomem *addr);
  18
  19 struct NS16550 {
  20         /* this struct must be packed */
  21         unsigned char rbr;  /* 0 */
  22         unsigned char ier;  /* 1 */
  23         unsigned char fcr;  /* 2 */
  24         unsigned char lcr;  /* 3 */
  25         unsigned char mcr;  /* 4 */
  26         unsigned char lsr;  /* 5 */
  27         unsigned char msr;  /* 6 */
  28         unsigned char scr;  /* 7 */
  29 };
  30
  31 #define thr rbr
  32 #define iir fcr
  33 #define dll rbr
  34 #define dlm ier
  35 #define dlab lcr
  36
  37 #define LSR_DR   0x01  /* Data ready */
  38 #define LSR_OE   0x02  /* Overrun */
  39 #define LSR_PE   0x04  /* Parity error */
  40 #define LSR_FE   0x08  /* Framing error */
  41 #define LSR_BI   0x10  /* Break */
  42 #define LSR_THRE 0x20  /* Xmit holding register empty */
  43 #define LSR_TEMT 0x40  /* Xmitter empty */
  44 #define LSR_ERR  0x80  /* Error */
  45
  46 #define LCR_DLAB 0x80
  47
  48 static volatile struct NS16550 __iomem *udbg_comport;
  49
  50 static void udbg_550_putc(char c)
  51 {
  52         if (udbg_comport) {
  53                 while ((in_8(&udbg_comport->lsr) & LSR_THRE) == 0)
  54                         /* wait for idle */;
  55                 out_8(&udbg_comport->thr, c);
  56                 if (c == '\n')
  57                         udbg_550_putc('\r');
  58         }
  59 }
  60
  61 static int udbg_550_getc_poll(void)
  62 {
  63         if (udbg_comport) {
  64                 if ((in_8(&udbg_comport->lsr) & LSR_DR) != 0)
  65                         return in_8(&udbg_comport->rbr);
  66                 else
  67                         return -1;
  68         }
  69         return -1;
  70 }
  71
  72 static char udbg_550_getc(void)
  73 {
  74         if (udbg_comport) {
  75                 while ((in_8(&udbg_comport->lsr) & LSR_DR) == 0)
  76                         /* wait for char */;
  77                 return in_8(&udbg_comport->rbr);
  78         }
  79         return 0;
  80 }
  81
  82 void udbg_init_uart(void __iomem *comport, unsigned int speed,
  83                     unsigned int clock)
  84 {
  85         unsigned int dll, base_bauds = clock / 16;
  86
  87         if (speed == 0)
  88                 speed = 9600;
  89         dll = base_bauds / speed;
  90
  91         if (comport) {
  92                 udbg_comport = (struct NS16550 __iomem *)comport;
  93                 out_8(&udbg_comport->lcr, 0x00);
  94                 out_8(&udbg_comport->ier, 0xff);
  95                 out_8(&udbg_comport->ier, 0x00);
  96                 out_8(&udbg_comport->lcr, LCR_DLAB);
  97                 out_8(&udbg_comport->dll, dll & 0xff);
  98                 out_8(&udbg_comport->dlm, dll >> 8);
  99                 /* 8 data, 1 stop, no parity */
 100                 out_8(&udbg_comport->lcr, 0x03);
 101                 /* RTS/DTR */
 102                 out_8(&udbg_comport->mcr, 0x03);
 103                 /* Clear & enable FIFOs */
 104                 out_8(&udbg_comport->fcr ,0x07);
 105                 udbg_putc = udbg_550_putc;
 106                 udbg_getc = udbg_550_getc;
 107                 udbg_getc_poll = udbg_550_getc_poll;
 108         }
 109 }
 110
 111 unsigned int udbg_probe_uart_speed(void __iomem *comport, unsigned int clock)
 112 {
 113         unsigned int dll, dlm, divisor, prescaler, speed;
 114         u8 old_lcr;
 115         volatile struct NS16550 __iomem *port = comport;
 116
 117         old_lcr = in_8(&port->lcr);
 118
 119         /* select divisor latch registers.  */
 120         out_8(&port->lcr, LCR_DLAB);
 121
 122         /* now, read the divisor */
 123         dll = in_8(&port->dll);
 124         dlm = in_8(&port->dlm);
 125         divisor = dlm << 8 | dll;
 126
 127         /* check prescaling */
 128         if (in_8(&port->mcr) & 0x80)
 129                 prescaler = 4;
 130         else
 131                 prescaler = 1;
 132
 133         /* restore the LCR */
 134         out_8(&port->lcr, old_lcr);
 135
 136         /* calculate speed */
 137         speed = (clock / prescaler) / (divisor * 16);
 138
 139         /* sanity check */
 140         if (speed < 9600 || speed > 115200)
 141                 speed = 9600;
 142
 143         return speed;
 144 }
 145
 146 #ifdef CONFIG_PPC_MAPLE
 147 void udbg_maple_real_putc(unsigned char c)
 148 {
 149         if (udbg_comport) {
 150                 while ((real_readb(&udbg_comport->lsr) & LSR_THRE) == 0)
 151                         /* wait for idle */;
 152                 real_writeb(c, &udbg_comport->thr); eieio();
 153                 if (c == '\n')
 154                         udbg_maple_real_putc('\r');
 155         }
 156 }
 157
 158 void udbg_init_maple_realmode(void)
 159 {
 160         udbg_comport = (volatile struct NS16550 __iomem *)0xf40003f8;
 161
 162         udbg_putc = udbg_maple_real_putc;
 163         udbg_getc = NULL;
 164         udbg_getc_poll = NULL;
 165 }
 166 #endif /* CONFIG_PPC_MAPLE */