drivers/serial/opencores_yanu.c

   1 /*
   2  * Copyright 2010, Renato Andreola <renato.andreola@imagos.it>
   3  *
   4  * See file CREDITS for list of people who contributed to this
   5  * project.
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2 of
  10  * the License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  20  * MA 02111-1307 USA
  21  */
  22
  23 #include <common.h>
  24 #include <watchdog.h>
  25 #include <asm/io.h>
  26 #include <nios2-yanu.h>
  27
  28 DECLARE_GLOBAL_DATA_PTR;
  29
  30 /*-----------------------------------------------------------------*/
  31 /* YANU Imagos serial port */
  32 /*-----------------------------------------------------------------*/
  33
  34 static yanu_uart_t *uart = (yanu_uart_t *)CONFIG_SYS_NIOS_CONSOLE;
  35
  36 #if defined(CONFIG_SYS_NIOS_FIXEDBAUD)
  37
  38 /* Everything's already setup for fixed-baud PTF assignment*/
  39
  40 static void oc_serial_setbrg(void)
  41 {
  42         int n, k;
  43         const unsigned max_uns = 0xFFFFFFFF;
  44         unsigned best_n, best_m, baud;
  45
  46         /* compute best N and M couple */
  47         best_n = YANU_MAX_PRESCALER_N;
  48         for (n = YANU_MAX_PRESCALER_N; n >= 0; n--) {
  49                 if ((unsigned)CONFIG_SYS_CLK_FREQ / (1 << (n + 4)) >=
  50                     (unsigned)CONFIG_BAUDRATE) {
  51                         best_n = n;
  52                         break;
  53                 }
  54         }
  55         for (k = 0;; k++) {
  56                 if ((unsigned)CONFIG_BAUDRATE <= (max_uns >> (15+n-k)))
  57                         break;
  58         }
  59         best_m =
  60             ((unsigned)CONFIG_BAUDRATE * (1 << (15 + n - k))) /
  61             ((unsigned)CONFIG_SYS_CLK_FREQ >> k);
  62
  63         baud = best_m + best_n * YANU_BAUDE;
  64         writel(baud, &uart->baud);
  65
  66         return;
  67 }
  68
  69 #else
  70
  71 static void oc_serial_setbrg(void)
  72 {
  73         int n, k;
  74         const unsigned max_uns = 0xFFFFFFFF;
  75         unsigned best_n, best_m, baud;
  76
  77         /* compute best N and M couple */
  78         best_n = YANU_MAX_PRESCALER_N;
  79         for (n = YANU_MAX_PRESCALER_N; n >= 0; n--) {
  80                 if ((unsigned)CONFIG_SYS_CLK_FREQ / (1 << (n + 4)) >=
  81                     gd->baudrate) {
  82                         best_n = n;
  83                         break;
  84                 }
  85         }
  86         for (k = 0;; k++) {
  87                 if (gd->baudrate <= (max_uns >> (15+n-k)))
  88                         break;
  89         }
  90         best_m =
  91             (gd->baudrate * (1 << (15 + n - k))) /
  92             ((unsigned)CONFIG_SYS_CLK_FREQ >> k);
  93
  94         baud = best_m + best_n * YANU_BAUDE;
  95         writel(baud, &uart->baud);
  96
  97         return;
  98 }
  99
 100
 101 #endif /* CONFIG_SYS_NIOS_FIXEDBAUD */
 102
 103 static int oc_serial_init(void)
 104 {
 105         unsigned action,control;
 106
 107         /* status register cleanup */
 108         action =  YANU_ACTION_RRRDY     |
 109                 YANU_ACTION_RTRDY       |
 110                 YANU_ACTION_ROE         |
 111                 YANU_ACTION_RBRK        |
 112                 YANU_ACTION_RFE         |
 113                 YANU_ACTION_RPE         |
 114             YANU_ACTION_RFE | YANU_ACTION_RFIFO_CLEAR | YANU_ACTION_TFIFO_CLEAR;
 115
 116         writel(action, &uart->action);
 117
 118         /*
 119          * control register cleanup
 120          * no interrupts enabled
 121          * one stop bit
 122          * hardware flow control disabled
 123          * 8 bits
 124          */
 125         control = (0x7 << YANU_CONTROL_BITS_POS);
 126         /* enven parity just to be clean */
 127         control |= YANU_CONTROL_PAREVEN;
 128         /* we set threshold for fifo */
 129         control |= YANU_CONTROL_RDYDLY * YANU_RXFIFO_DLY;
 130         control |= YANU_CONTROL_TXTHR *  YANU_TXFIFO_THR;
 131
 132         writel(control, &uart->control);
 133
 134         /* to set baud rate */
 135         serial_setbrg();
 136
 137         return (0);
 138 }
 139
 140
 141 /*-----------------------------------------------------------------------
 142  * YANU CONSOLE
 143  *---------------------------------------------------------------------*/
 144 static void oc_serial_putc(char c)
 145 {
 146         int tx_chars;
 147         unsigned status;
 148
 149         if (c == '\n')
 150                 serial_putc ('\r');
 151
 152         while (1) {
 153                 status = readl(&uart->status);
 154                 tx_chars = (status>>YANU_TFIFO_CHARS_POS)
 155                         & ((1<<YANU_TFIFO_CHARS_N)-1);
 156                 if (tx_chars < YANU_TXFIFO_SIZE-1)
 157                         break;
 158                 WATCHDOG_RESET ();
 159         }
 160
 161         writel((unsigned char)c, &uart->data);
 162 }
 163
 164 static int oc_serial_tstc(void)
 165 {
 166         unsigned status ;
 167
 168         status = readl(&uart->status);
 169         return (((status >> YANU_RFIFO_CHARS_POS) &
 170                  ((1 << YANU_RFIFO_CHARS_N) - 1)) > 0);
 171 }
 172
 173 statoc int oc_serial_getc(void)
 174 {
 175         while (serial_tstc() == 0)
 176                 WATCHDOG_RESET ();
 177
 178         /* first we pull the char */
 179         writel(YANU_ACTION_RFIFO_PULL, &uart->action);
 180
 181         return(readl(&uart->data) & YANU_DATA_CHAR_MASK);
 182 }
 183
 184 static struct serial_device oc_serial_drv = {
 185         .name   = "oc_serial",
 186         .start  = oc_serial_init,
 187         .stop   = NULL,
 188         .setbrg = oc_serial_setbrg,
 189         .putc   = oc_serial_putc,
 190         .puts   = default_serial_puts,
 191         .getc   = oc_serial_getc,
 192         .tstc   = oc_serial_tstc,
 193 };
 194
 195 void oc_serial_initialize(void)
 196 {
 197         serial_register(&oc_serial_drv);
 198 }
 199
 200 __weak struct serial_device *default_serial_console(void)
 201 {
 202         return &oc_serial_drv;
 203 }