drivers/serial/atmel_usart.c

   1 /*
   2  * Copyright (C) 2004-2006 Atmel Corporation
   3  *
   4  * Modified to support C structur SoC access by
   5  * Andreas Bießmann <biessmann@corscience.de>
   6  *
   7  * SPDX-License-Identifier:     GPL-2.0+
   8  */
   9 #include <common.h>
  10 #include <watchdog.h>
  11 #include <serial.h>
  12 #include <linux/compiler.h>
  13
  14 #include <asm/io.h>
  15 #include <asm/arch/clk.h>
  16 #include <asm/arch/hardware.h>
  17
  18 #include "atmel_usart.h"
  19
  20 DECLARE_GLOBAL_DATA_PTR;
  21
  22 static void atmel_serial_setbrg(void)
  23 {
  24         atmel_usart3_t *usart = (atmel_usart3_t *)CONFIG_USART_BASE;
  25         unsigned long divisor;
  26         unsigned long usart_hz;
  27
  28         /*
  29          *              Master Clock
  30          * Baud Rate = --------------
  31          *                16 * CD
  32          */
  33         usart_hz = get_usart_clk_rate(CONFIG_USART_ID);
  34         divisor = (usart_hz / 16 + gd->baudrate / 2) / gd->baudrate;
  35         writel(USART3_BF(CD, divisor), &usart->brgr);
  36 }
  37
  38 static int atmel_serial_init(void)
  39 {
  40         atmel_usart3_t *usart = (atmel_usart3_t *)CONFIG_USART_BASE;
  41
  42         /*
  43          * Just in case: drain transmitter register
  44          * 1000us is enough for baudrate >= 9600
  45          */
  46         if (!(readl(&usart->csr) & USART3_BIT(TXEMPTY)))
  47                 __udelay(1000);
  48
  49         writel(USART3_BIT(RSTRX) | USART3_BIT(RSTTX), &usart->cr);
  50
  51         serial_setbrg();
  52
  53         writel((USART3_BF(USART_MODE, USART3_USART_MODE_NORMAL)
  54                            | USART3_BF(USCLKS, USART3_USCLKS_MCK)
  55                            | USART3_BF(CHRL, USART3_CHRL_8)
  56                            | USART3_BF(PAR, USART3_PAR_NONE)
  57                            | USART3_BF(NBSTOP, USART3_NBSTOP_1)),
  58                            &usart->mr);
  59         writel(USART3_BIT(RXEN) | USART3_BIT(TXEN), &usart->cr);
  60         /* 100us is enough for the new settings to be settled */
  61         __udelay(100);
  62
  63         return 0;
  64 }
  65
  66 static void atmel_serial_putc(char c)
  67 {
  68         atmel_usart3_t *usart = (atmel_usart3_t *)CONFIG_USART_BASE;
  69
  70         if (c == '\n')
  71                 serial_putc('\r');
  72
  73         while (!(readl(&usart->csr) & USART3_BIT(TXRDY)));
  74         writel(c, &usart->thr);
  75 }
  76
  77 static int atmel_serial_getc(void)
  78 {
  79         atmel_usart3_t *usart = (atmel_usart3_t *)CONFIG_USART_BASE;
  80
  81         while (!(readl(&usart->csr) & USART3_BIT(RXRDY)))
  82                  WATCHDOG_RESET();
  83         return readl(&usart->rhr);
  84 }
  85
  86 static int atmel_serial_tstc(void)
  87 {
  88         atmel_usart3_t *usart = (atmel_usart3_t *)CONFIG_USART_BASE;
  89         return (readl(&usart->csr) & USART3_BIT(RXRDY)) != 0;
  90 }
  91
  92 static struct serial_device atmel_serial_drv = {
  93         .name   = "atmel_serial",
  94         .start  = atmel_serial_init,
  95         .stop   = NULL,
  96         .setbrg = atmel_serial_setbrg,
  97         .putc   = atmel_serial_putc,
  98         .puts   = default_serial_puts,
  99         .getc   = atmel_serial_getc,
 100         .tstc   = atmel_serial_tstc,
 101 };
 102
 103 void atmel_serial_initialize(void)
 104 {
 105         serial_register(&atmel_serial_drv);
 106 }
 107
 108 __weak struct serial_device *default_serial_console(void)
 109 {
 110         return &atmel_serial_drv;
 111 }