forked from luck/tmp_suning_uos_patched
d1a1af2cdf
Add DCC earlycon support for early printks. The patch is useful for SoC bringup where HW serial console is broken. Signed-off-by: Michal Simek <michal.simek@xilinx.com> Link: https://lore.kernel.org/r/41e2920a6348e65b2e986b0e65b66531e87cd756.1570543923.git.michal.simek@xilinx.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
116 lines
2.2 KiB
C
116 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/* Copyright (c) 2010, 2014 The Linux Foundation. All rights reserved. */
|
|
|
|
#include <linux/console.h>
|
|
#include <linux/init.h>
|
|
#include <linux/serial.h>
|
|
#include <linux/serial_core.h>
|
|
|
|
#include <asm/dcc.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 void dcc_uart_console_putchar(struct uart_port *port, int ch)
|
|
{
|
|
while (__dcc_getstatus() & DCC_STATUS_TX)
|
|
cpu_relax();
|
|
|
|
__dcc_putchar(ch);
|
|
}
|
|
|
|
static void dcc_early_write(struct console *con, const char *s, unsigned n)
|
|
{
|
|
struct earlycon_device *dev = con->data;
|
|
|
|
uart_console_write(&dev->port, s, n, dcc_uart_console_putchar);
|
|
}
|
|
|
|
static int __init dcc_early_console_setup(struct earlycon_device *device,
|
|
const char *opt)
|
|
{
|
|
device->con->write = dcc_early_write;
|
|
|
|
return 0;
|
|
}
|
|
|
|
EARLYCON_DECLARE(dcc, dcc_early_console_setup);
|
|
|
|
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 bool hvc_dcc_check(void)
|
|
{
|
|
unsigned long time = jiffies + (HZ / 10);
|
|
|
|
/* Write a test character to check if it is handled */
|
|
__dcc_putchar('\n');
|
|
|
|
while (time_is_after_jiffies(time)) {
|
|
if (!(__dcc_getstatus() & DCC_STATUS_TX))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
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)
|
|
{
|
|
int ret;
|
|
|
|
if (!hvc_dcc_check())
|
|
return -ENODEV;
|
|
|
|
/* Returns -1 if error */
|
|
ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
|
|
|
|
return ret < 0 ? -ENODEV : 0;
|
|
}
|
|
console_initcall(hvc_dcc_console_init);
|
|
|
|
static int __init hvc_dcc_init(void)
|
|
{
|
|
struct hvc_struct *p;
|
|
|
|
if (!hvc_dcc_check())
|
|
return -ENODEV;
|
|
|
|
p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
|
|
|
|
return PTR_ERR_OR_ZERO(p);
|
|
}
|
|
device_initcall(hvc_dcc_init);
|