LXR linux/drivers/tty/hvc/hvc

   1/* Copyright (c) 2010, 2014 The Linux Foundation. All rights reserved.
   2 *
   3 * This program is free software; you can redistribute it and/or modify
   4 * it under the terms of the GNU General Public License version 2 and
   5 * only version 2 as published by the Free Software Foundation.
   6 *
   7 * This program is distributed in the hope that it will be useful,
   8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10 * GNU General Public License for more details.
  11 */
  12
  13#include <linux/init.h>
  14
  15#include <asm/dcc.h>
  16#include <asm/processor.h>
  17
  18#include "hvc_console.h"
  19
  20/* DCC Status Bits */
  21#define DCC_STATUS_RX           (1 << 30)
  22#define DCC_STATUS_TX           (1 << 29)
  23
  24static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
  25{
  26        int i;
  27
  28        for (i = 0; i < count; i++) {
  29                while (__dcc_getstatus() & DCC_STATUS_TX)
  30                        cpu_relax();
  31
  32                __dcc_putchar(buf[i]);
  33        }
  34
  35        return count;
  36}
  37
  38static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
  39{
  40        int i;
  41
  42        for (i = 0; i < count; ++i)
  43                if (__dcc_getstatus() & DCC_STATUS_RX)
  44                        buf[i] = __dcc_getchar();
  45                else
  46                        break;
  47
  48        return i;
  49}
  50
  51static bool hvc_dcc_check(void)
  52{
  53        unsigned long time = jiffies + (HZ / 10);
  54
  55        /* Write a test character to check if it is handled */
  56        __dcc_putchar('\n');
  57
  58        while (time_is_after_jiffies(time)) {
  59                if (!(__dcc_getstatus() & DCC_STATUS_TX))
  60                        return true;
  61        }
  62
  63        return false;
  64}
  65
  66static const struct hv_ops hvc_dcc_get_put_ops = {
  67        .get_chars = hvc_dcc_get_chars,
  68        .put_chars = hvc_dcc_put_chars,
  69};
  70
  71static int __init hvc_dcc_console_init(void)
  72{
  73        int ret;
  74
  75        if (!hvc_dcc_check())
  76                return -ENODEV;
  77
  78        /* Returns -1 if error */
  79        ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
  80
  81        return ret < 0 ? -ENODEV : 0;
  82}
  83console_initcall(hvc_dcc_console_init);
  84
  85static int __init hvc_dcc_init(void)
  86{
  87        struct hvc_struct *p;
  88
  89        if (!hvc_dcc_check())
  90                return -ENODEV;
  91
  92        p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
  93
  94        return PTR_ERR_OR_ZERO(p);
  95}
  96device_initcall(hvc_dcc_init);
  97