116 строки
2.2 KiB
C
116 строки
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2010, 2014 The Linux Foundation. All rights reserved. */
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#include <linux/console.h>
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#include <linux/init.h>
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#include <linux/serial.h>
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#include <linux/serial_core.h>
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#include <asm/dcc.h>
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#include <asm/processor.h>
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#include "hvc_console.h"
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/* DCC Status Bits */
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#define DCC_STATUS_RX (1 << 30)
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#define DCC_STATUS_TX (1 << 29)
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static void dcc_uart_console_putchar(struct uart_port *port, unsigned char ch)
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{
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while (__dcc_getstatus() & DCC_STATUS_TX)
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cpu_relax();
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__dcc_putchar(ch);
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}
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static void dcc_early_write(struct console *con, const char *s, unsigned n)
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{
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struct earlycon_device *dev = con->data;
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uart_console_write(&dev->port, s, n, dcc_uart_console_putchar);
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}
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static int __init dcc_early_console_setup(struct earlycon_device *device,
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const char *opt)
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{
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device->con->write = dcc_early_write;
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return 0;
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}
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EARLYCON_DECLARE(dcc, dcc_early_console_setup);
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static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
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{
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int i;
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for (i = 0; i < count; i++) {
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while (__dcc_getstatus() & DCC_STATUS_TX)
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cpu_relax();
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__dcc_putchar(buf[i]);
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}
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return count;
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}
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static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
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{
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int i;
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for (i = 0; i < count; ++i)
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if (__dcc_getstatus() & DCC_STATUS_RX)
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buf[i] = __dcc_getchar();
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else
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break;
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return i;
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}
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static bool hvc_dcc_check(void)
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{
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unsigned long time = jiffies + (HZ / 10);
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/* Write a test character to check if it is handled */
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__dcc_putchar('\n');
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while (time_is_after_jiffies(time)) {
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if (!(__dcc_getstatus() & DCC_STATUS_TX))
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return true;
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}
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return false;
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}
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static const struct hv_ops hvc_dcc_get_put_ops = {
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.get_chars = hvc_dcc_get_chars,
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.put_chars = hvc_dcc_put_chars,
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};
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static int __init hvc_dcc_console_init(void)
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{
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int ret;
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if (!hvc_dcc_check())
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return -ENODEV;
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/* Returns -1 if error */
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ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
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return ret < 0 ? -ENODEV : 0;
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}
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console_initcall(hvc_dcc_console_init);
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static int __init hvc_dcc_init(void)
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{
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struct hvc_struct *p;
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if (!hvc_dcc_check())
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return -ENODEV;
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p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
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return PTR_ERR_OR_ZERO(p);
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}
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device_initcall(hvc_dcc_init);
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