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tty: goldfish: Implement support for kernel 'earlycon' parameter

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Add early console functionality to the Goldfish tty driver.

When 'earlycon' kernel command line parameter is used with no options,
the early console is determined by the 'stdout-path' property in device
tree's 'chosen' node. This is illustrated in the following device tree
source example:

Device tree example:

    chosen {
        stdout-path = "/goldfish_tty@1f004000";
    };

    goldfish_tty@1f004000 {
        interrupts = <0xc>;
        reg = <0x1f004000 0x0 0x1000>;
        compatible = "google,goldfish-tty";
    };

Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Miodrag Dinic 2017-08-29 15:53:20 +02:00 committed by Greg Kroah-Hartman
parent 7157d2be23
commit 3840ed9548
2 changed files with 29 additions and 0 deletions
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3
drivers/tty/Kconfig
View file

@ -392,6 +392,9 @@ config PPC_EARLY_DEBUG_EHV_BC_HANDLE
config GOLDFISH_TTY
tristate "Goldfish TTY Driver"
depends on GOLDFISH
select SERIAL_CORE
select SERIAL_CORE_CONSOLE
select SERIAL_EARLYCON
help
Console and system TTY driver for the Goldfish virtual platform.

26
drivers/tty/goldfish.c
View file

@ -1,6 +1,7 @@
/*
* Copyright (C) 2007 Google, Inc.
* Copyright (C) 2012 Intel, Inc.
* Copyright (C) 2017 Imagination Technologies Ltd.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
@ -24,6 +25,7 @@
#include <linux/goldfish.h>
#include <linux/mm.h>
#include <linux/dma-mapping.h>
#include <linux/serial_core.h>
/* Goldfish tty register's offsets */
#define GOLDFISH_TTY_REG_BYTES_READY 0x04
@ -440,6 +442,30 @@ static int goldfish_tty_remove(struct platform_device *pdev)
return 0;
}
static void gf_early_console_putchar(struct uart_port *port, int ch)
{
__raw_writel(ch, port->membase);
}
static void gf_early_write(struct console *con, const char *s, unsigned int n)
{
struct earlycon_device *dev = con->data;
uart_console_write(&dev->port, s, n, gf_early_console_putchar);
}
static int __init gf_earlycon_setup(struct earlycon_device *device,
const char *opt)
{
if (!device->port.membase)
return -ENODEV;
device->con->write = gf_early_write;
return 0;
}
OF_EARLYCON_DECLARE(early_gf_tty, "google,goldfish-tty", gf_earlycon_setup);
static const struct of_device_id goldfish_tty_of_match[] = {
{ .compatible = "google,goldfish-tty", },
{},