hvc_dcc.c

Go to the documentation of this file.

/* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/console.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/types.h>

#include <asm/processor.h>

#include "hvc_console.h"

/* DCC Status Bits */
#define DCC_STATUS_RX       (1 << 30)
#define DCC_STATUS_TX       (1 << 29)

static inline u32 __dcc_getstatus(void)
{
    u32 __ret;
    asm volatile("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg"
        : "=r" (__ret) : : "cc");

    return __ret;
}


static inline char __dcc_getchar(void)
{
    char __c;

    asm volatile("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg"
        : "=r" (__c));
    isb();

    return __c;
}

static inline void __dcc_putchar(char c)
{
    asm volatile("mcr p14, 0, %0, c0, c5, 0 @ write a char"
        : /* no output register */
        : "r" (c));
    isb();
}

static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
{
    int i;

    for (i = 0; i < count; i++) {
        while (__dcc_getstatus() & DCC_STATUS_TX)
            cpu_relax();

        __dcc_putchar(buf[i]);
    }

    return count;
}

static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
{
    int i;

    for (i = 0; i < count; ++i)
        if (__dcc_getstatus() & DCC_STATUS_RX)
            buf[i] = __dcc_getchar();
        else
            break;

    return i;
}

static const struct hv_ops hvc_dcc_get_put_ops = {
    .get_chars = hvc_dcc_get_chars,
    .put_chars = hvc_dcc_put_chars,
};

static int __init hvc_dcc_console_init(void)
{
    hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
    return 0;
}
console_initcall(hvc_dcc_console_init);

static int __init hvc_dcc_init(void)
{
    hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
    return 0;
}
device_initcall(hvc_dcc_init);