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Subject[PATCH v4 03/16] tty: goldfish: Implement support for kernel 'earlycon' parameter
Date
From: Miodrag Dinic <miodrag.dinic@imgtec.com>

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", "generic,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>
---
drivers/tty/Kconfig | 3 +++
drivers/tty/goldfish.c | 26 ++++++++++++++++++++++++++
2 files changed, 29 insertions(+)

diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 9510305..873e0ba 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -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.

diff --git a/drivers/tty/goldfish.c b/drivers/tty/goldfish.c
index acd50fa..22b7ad5 100644
--- a/drivers/tty/goldfish.c
+++ b/drivers/tty/goldfish.c
@@ -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>

enum {
GOLDFISH_TTY_PUT_CHAR = 0x00,
@@ -427,6 +429,30 @@ 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", },
{},
--
2.7.4
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