drivers/serial/s3c64xx.c

   1 /*
   2  * (C) Copyright 2002
   3  * Gary Jennejohn, DENX Software Engineering, <garyj@denx.de>
   4  *
   5  * (C) Copyright 2008
   6  * Guennadi Liakhovetki, DENX Software Engineering, <lg@denx.de>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  *
  22  */
  23
  24 #include <common.h>
  25
  26 #include <s3c6400.h>
  27
  28 #ifdef CONFIG_SERIAL1
  29 #define UART_NR S3C64XX_UART0
  30
  31 #elif defined(CONFIG_SERIAL2)
  32 #define UART_NR S3C64XX_UART1
  33
  34 #elif defined(CONFIG_SERIAL3)
  35 #define UART_NR S3C64XX_UART2
  36
  37 #else
  38 #error "Bad: you didn't configure serial ..."
  39 #endif
  40
  41 #define barrier() asm volatile("" ::: "memory")
  42
  43 /*
  44  * The coefficient, used to calculate the baudrate on S3C6400 UARTs is
  45  * calculated as
  46  * C = UBRDIV * 16 + number_of_set_bits_in_UDIVSLOT
  47  * however, section 31.6.11 of the datasheet doesn't recomment using 1 for 1,
  48  * 3 for 2, ... (2^n - 1) for n, instead, they suggest using these constants:
  49  */
  50 static const int udivslot[] = {
  51         0,
  52         0x0080,
  53         0x0808,
  54         0x0888,
  55         0x2222,
  56         0x4924,
  57         0x4a52,
  58         0x54aa,
  59         0x5555,
  60         0xd555,
  61         0xd5d5,
  62         0xddd5,
  63         0xdddd,
  64         0xdfdd,
  65         0xdfdf,
  66         0xffdf,
  67 };
  68
  69 void serial_setbrg(void)
  70 {
  71         DECLARE_GLOBAL_DATA_PTR;
  72         s3c64xx_uart *const uart = s3c64xx_get_base_uart(UART_NR);
  73         u32 pclk = get_PCLK();
  74         u32 baudrate = gd->baudrate;
  75         int i;
  76
  77         i = (pclk / baudrate) % 16;
  78
  79         uart->UBRDIV = pclk / baudrate / 16 - 1;
  80         uart->UDIVSLOT = udivslot[i];
  81
  82         for (i = 0; i < 100; i++)
  83                 barrier();
  84 }
  85
  86 /*
  87  * Initialise the serial port with the given baudrate. The settings
  88  * are always 8 data bits, no parity, 1 stop bit, no start bits.
  89  */
  90 int serial_init(void)
  91 {
  92         s3c64xx_uart *const uart = s3c64xx_get_base_uart(UART_NR);
  93
  94         /* reset and enable FIFOs, set triggers to the maximum */
  95         uart->UFCON = 0xff;
  96         uart->UMCON = 0;
  97         /* 8N1 */
  98         uart->ULCON = 3;
  99         /* No interrupts, no DMA, pure polling */
 100         uart->UCON = 5;
 101
 102         serial_setbrg();
 103
 104         return 0;
 105 }
 106
 107 /*
 108  * Read a single byte from the serial port. Returns 1 on success, 0
 109  * otherwise. When the function is succesfull, the character read is
 110  * written into its argument c.
 111  */
 112 int serial_getc(void)
 113 {
 114         s3c64xx_uart *const uart = s3c64xx_get_base_uart(UART_NR);
 115
 116         /* wait for character to arrive */
 117         while (!(uart->UTRSTAT & 0x1));
 118
 119         return uart->URXH & 0xff;
 120 }
 121
 122 #ifdef CONFIG_MODEM_SUPPORT
 123 static int be_quiet;
 124 void disable_putc(void)
 125 {
 126         be_quiet = 1;
 127 }
 128
 129 void enable_putc(void)
 130 {
 131         be_quiet = 0;
 132 }
 133 #endif
 134
 135
 136 /*
 137  * Output a single byte to the serial port.
 138  */
 139 void serial_putc(const char c)
 140 {
 141         s3c64xx_uart *const uart = s3c64xx_get_base_uart(UART_NR);
 142
 143 #ifdef CONFIG_MODEM_SUPPORT
 144         if (be_quiet)
 145                 return;
 146 #endif
 147
 148         /* wait for room in the tx FIFO */
 149         while (!(uart->UTRSTAT & 0x2));
 150
 151         uart->UTXH = c;
 152
 153         /* If \n, also do \r */
 154         if (c == '\n')
 155                 serial_putc('\r');
 156 }
 157
 158 /*
 159  * Test whether a character is in the RX buffer
 160  */
 161 int serial_tstc(void)
 162 {
 163         s3c64xx_uart *const uart = s3c64xx_get_base_uart(UART_NR);
 164
 165         return uart->UTRSTAT & 0x1;
 166 }
 167
 168 void serial_puts(const char *s)
 169 {
 170         while (*s)
 171                 serial_putc(*s++);
 172 }