drivers/serial/opencores_yanu.c

   1 /*
   2  * Copyright 2010, Renato Andreola <renato.andreola@imagos.it>
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 #include <common.h>
   8 #include <watchdog.h>
   9 #include <asm/io.h>
  10 #include <nios2-yanu.h>
  11 #include <serial.h>
  12
  13 DECLARE_GLOBAL_DATA_PTR;
  14
  15 /*-----------------------------------------------------------------*/
  16 /* YANU Imagos serial port */
  17 /*-----------------------------------------------------------------*/
  18
  19 static yanu_uart_t *uart = (yanu_uart_t *)CONFIG_SYS_NIOS_CONSOLE;
  20
  21 static void oc_serial_setbrg(void)
  22 {
  23         int n, k;
  24         const unsigned max_uns = 0xFFFFFFFF;
  25         unsigned best_n, best_m, baud;
  26         unsigned baudrate;
  27
  28 #if defined(CONFIG_SYS_NIOS_FIXEDBAUD)
  29         /* Everything's already setup for fixed-baud PTF assignment */
  30         baudrate = CONFIG_BAUDRATE;
  31 #else
  32         baudrate = gd->baudrate;
  33 #endif
  34         /* compute best N and M couple */
  35         best_n = YANU_MAX_PRESCALER_N;
  36         for (n = YANU_MAX_PRESCALER_N; n >= 0; n--) {
  37                 if ((unsigned)CONFIG_SYS_CLK_FREQ / (1 << (n + 4)) >=
  38                     baudrate) {
  39                         best_n = n;
  40                         break;
  41                 }
  42         }
  43         for (k = 0;; k++) {
  44                 if (baudrate <= (max_uns >> (15+n-k)))
  45                         break;
  46         }
  47         best_m =
  48             (baudrate * (1 << (15 + n - k))) /
  49             ((unsigned)CONFIG_SYS_CLK_FREQ >> k);
  50
  51         baud = best_m + best_n * YANU_BAUDE;
  52         writel(baud, &uart->baud);
  53
  54         return;
  55 }
  56
  57 static int oc_serial_init(void)
  58 {
  59         unsigned action,control;
  60
  61         /* status register cleanup */
  62         action =  YANU_ACTION_RRRDY     |
  63                 YANU_ACTION_RTRDY       |
  64                 YANU_ACTION_ROE         |
  65                 YANU_ACTION_RBRK        |
  66                 YANU_ACTION_RFE         |
  67                 YANU_ACTION_RPE         |
  68             YANU_ACTION_RFE | YANU_ACTION_RFIFO_CLEAR | YANU_ACTION_TFIFO_CLEAR;
  69
  70         writel(action, &uart->action);
  71
  72         /*
  73          * control register cleanup
  74          * no interrupts enabled
  75          * one stop bit
  76          * hardware flow control disabled
  77          * 8 bits
  78          */
  79         control = (0x7 << YANU_CONTROL_BITS_POS);
  80         /* enven parity just to be clean */
  81         control |= YANU_CONTROL_PAREVEN;
  82         /* we set threshold for fifo */
  83         control |= YANU_CONTROL_RDYDLY * YANU_RXFIFO_DLY;
  84         control |= YANU_CONTROL_TXTHR *  YANU_TXFIFO_THR;
  85
  86         writel(control, &uart->control);
  87
  88         /* to set baud rate */
  89         serial_setbrg();
  90
  91         return (0);
  92 }
  93
  94
  95 /*-----------------------------------------------------------------------
  96  * YANU CONSOLE
  97  *---------------------------------------------------------------------*/
  98 static void oc_serial_putc(char c)
  99 {
 100         int tx_chars;
 101         unsigned status;
 102
 103         if (c == '\n')
 104                 serial_putc ('\r');
 105
 106         while (1) {
 107                 status = readl(&uart->status);
 108                 tx_chars = (status>>YANU_TFIFO_CHARS_POS)
 109                         & ((1<<YANU_TFIFO_CHARS_N)-1);
 110                 if (tx_chars < YANU_TXFIFO_SIZE-1)
 111                         break;
 112                 WATCHDOG_RESET ();
 113         }
 114
 115         writel((unsigned char)c, &uart->data);
 116 }
 117
 118 static int oc_serial_tstc(void)
 119 {
 120         unsigned status ;
 121
 122         status = readl(&uart->status);
 123         return (((status >> YANU_RFIFO_CHARS_POS) &
 124                  ((1 << YANU_RFIFO_CHARS_N) - 1)) > 0);
 125 }
 126
 127 static int oc_serial_getc(void)
 128 {
 129         while (serial_tstc() == 0)
 130                 WATCHDOG_RESET ();
 131
 132         /* first we pull the char */
 133         writel(YANU_ACTION_RFIFO_PULL, &uart->action);
 134
 135         return(readl(&uart->data) & YANU_DATA_CHAR_MASK);
 136 }
 137
 138 static struct serial_device oc_serial_drv = {
 139         .name   = "oc_serial",
 140         .start  = oc_serial_init,
 141         .stop   = NULL,
 142         .setbrg = oc_serial_setbrg,
 143         .putc   = oc_serial_putc,
 144         .puts   = default_serial_puts,
 145         .getc   = oc_serial_getc,
 146         .tstc   = oc_serial_tstc,
 147 };
 148
 149 void oc_serial_initialize(void)
 150 {
 151         serial_register(&oc_serial_drv);
 152 }
 153
 154 __weak struct serial_device *default_serial_console(void)
 155 {
 156         return &oc_serial_drv;
 157 }