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hvc: dcc: Add earlycon support 

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>
This commit is contained in:
Michal Simek 2019-10-08 16:12:06 +02:00 committed by Greg Kroah-Hartman
parent 33364d63c7
commit d1a1af2cdf
1 changed files with 28 additions and 0 deletions
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28
drivers/tty/hvc/hvc_dcc.c
View File

@ -1,7 +1,10 @@
// 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>
@ -12,6 +15,31 @@
#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;