drivers/serial/altera_jtag_uart.c

   1 /*
   2  * (C) Copyright 2004, Psyent Corporation <www.psyent.com>
   3  * Scott McNutt <smcnutt@psyent.com>
   4  *
   5  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7
   8 #include <common.h>
   9 #include <watchdog.h>
  10 #include <asm/io.h>
  11 #include <linux/compiler.h>
  12 #include <serial.h>
  13
  14 typedef volatile struct {
  15         unsigned        data;                   /* Data register */
  16         unsigned        control;                /* Control register */
  17 } nios_jtag_t;
  18
  19 /* data register */
  20 #define NIOS_JTAG_RVALID        (1<<15)         /* Read valid */
  21 #define NIOS_JTAG_DATA(d)       ((d)&0x0ff)     /* Read data */
  22 #define NIOS_JTAG_RAVAIL(d)     ((d)>>16)       /* Read space avail */
  23
  24 /* control register */
  25 #define NIOS_JTAG_RE            (1 << 0)        /* read intr enable */
  26 #define NIOS_JTAG_WE            (1 << 1)        /* write intr enable */
  27 #define NIOS_JTAG_RI            (1 << 8)        /* read intr pending */
  28 #define NIOS_JTAG_WI            (1 << 9)        /* write intr pending*/
  29 #define NIOS_JTAG_AC            (1 << 10)       /* activity indicator */
  30 #define NIOS_JTAG_RRDY          (1 << 12)       /* read available */
  31 #define NIOS_JTAG_WSPACE(d)     ((d)>>16)       /* Write space avail */
  32
  33 DECLARE_GLOBAL_DATA_PTR;
  34
  35 /*------------------------------------------------------------------
  36  * JTAG acts as the serial port
  37  *-----------------------------------------------------------------*/
  38 static nios_jtag_t *jtag = (nios_jtag_t *)CONFIG_SYS_NIOS_CONSOLE;
  39
  40 static void altera_jtag_serial_setbrg(void)
  41 {
  42 }
  43
  44 static int altera_jtag_serial_init(void)
  45 {
  46         return 0;
  47 }
  48
  49 static void altera_jtag_serial_putc(char c)
  50 {
  51         while (1) {
  52                 unsigned st = readl(&jtag->control);
  53                 if (NIOS_JTAG_WSPACE(st))
  54                         break;
  55 #ifdef CONFIG_ALTERA_JTAG_UART_BYPASS
  56                 if (!(st & NIOS_JTAG_AC)) /* no connection */
  57                         return;
  58 #endif
  59                 WATCHDOG_RESET();
  60         }
  61         writel ((unsigned char)c, &jtag->data);
  62 }
  63
  64 static int altera_jtag_serial_tstc(void)
  65 {
  66         return ( readl (&jtag->control) & NIOS_JTAG_RRDY);
  67 }
  68
  69 static int altera_jtag_serial_getc(void)
  70 {
  71         int c;
  72         unsigned val;
  73
  74         while (1) {
  75                 WATCHDOG_RESET ();
  76                 val = readl (&jtag->data);
  77                 if (val & NIOS_JTAG_RVALID)
  78                         break;
  79         }
  80         c = val & 0x0ff;
  81         return (c);
  82 }
  83
  84 static struct serial_device altera_jtag_serial_drv = {
  85         .name   = "altera_jtag_uart",
  86         .start  = altera_jtag_serial_init,
  87         .stop   = NULL,
  88         .setbrg = altera_jtag_serial_setbrg,
  89         .putc   = altera_jtag_serial_putc,
  90         .puts   = default_serial_puts,
  91         .getc   = altera_jtag_serial_getc,
  92         .tstc   = altera_jtag_serial_tstc,
  93 };
  94
  95 void altera_jtag_serial_initialize(void)
  96 {
  97         serial_register(&altera_jtag_serial_drv);
  98 }
  99
 100 __weak struct serial_device *default_serial_console(void)
 101 {
 102         return &altera_jtag_serial_drv;
 103 }