serial: samsung: Add support for early console

This patch adds support for early console initialized from device tree
and kernel command line to all variants of Samsung serial driver.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
[mszyprow: added support for command line based initialization,
           fixed comments, added documentation]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 104 insertions, 0 deletions

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 35677f75a1d..c63317e87c3 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -241,6 +241,7 @@ config SERIAL_SAMSUNG
 	tristate "Samsung SoC serial support"
 	depends on PLAT_SAMSUNG || ARCH_EXYNOS
 	select SERIAL_CORE
+	select SERIAL_EARLYCON
 	help
 	  Support for the on-chip UARTs on the Samsung S3C24XX series CPUs,
 	  providing /dev/ttySAC0, 1 and 2 (note, some machines may not
diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 024e5ecee98..a6bef8dcdc3 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -2403,6 +2403,109 @@ static struct platform_driver samsung_serial_driver = {
 
 module_platform_driver(samsung_serial_driver);
 
+/*
+ * Early console.
+ */
+
+struct samsung_early_console_data {
+	u32 txfull_mask;
+};
+
+static void samsung_early_busyuart(struct uart_port *port)
+{
+	while (!(readl(port->membase + S3C2410_UTRSTAT) & S3C2410_UTRSTAT_TXFE))
+		;
+}
+
+static void samsung_early_busyuart_fifo(struct uart_port *port)
+{
+	struct samsung_early_console_data *data = port->private_data;
+
+	while (readl(port->membase + S3C2410_UFSTAT) & data->txfull_mask)
+		;
+}
+
+static void samsung_early_putc(struct uart_port *port, int c)
+{
+	if (readl(port->membase + S3C2410_UFCON) & S3C2410_UFCON_FIFOMODE)
+		samsung_early_busyuart_fifo(port);
+	else
+		samsung_early_busyuart(port);
+
+	writeb(c, port->membase + S3C2410_UTXH);
+}
+
+static void samsung_early_write(struct console *con, const char *s, unsigned n)
+{
+	struct earlycon_device *dev = con->data;
+
+	uart_console_write(&dev->port, s, n, samsung_early_putc);
+}
+
+static int __init samsung_early_console_setup(struct earlycon_device *device,
+					      const char *opt)
+{
+	if (!device->port.membase)
+		return -ENODEV;
+
+	device->con->write = samsung_early_write;
+	return 0;
+}
+
+/* S3C2410 */
+static struct samsung_early_console_data s3c2410_early_console_data = {
+	.txfull_mask = S3C2410_UFSTAT_TXFULL,
+};
+
+static int __init s3c2410_early_console_setup(struct earlycon_device *device,
+					      const char *opt)
+{
+	device->port.private_data = &s3c2410_early_console_data;
+	return samsung_early_console_setup(device, opt);
+}
+OF_EARLYCON_DECLARE(s3c2410, "samsung,s3c2410-uart",
+			s3c2410_early_console_setup);
+EARLYCON_DECLARE(s3c2410, s3c2410_early_console_setup);
+
+/* S3C2412, S3C2440, S3C64xx */
+static struct samsung_early_console_data s3c2440_early_console_data = {
+	.txfull_mask = S3C2440_UFSTAT_TXFULL,
+};
+
+static int __init s3c2440_early_console_setup(struct earlycon_device *device,
+					      const char *opt)
+{
+	device->port.private_data = &s3c2440_early_console_data;
+	return samsung_early_console_setup(device, opt);
+}
+OF_EARLYCON_DECLARE(s3c2412, "samsung,s3c2412-uart",
+			s3c2440_early_console_setup);
+OF_EARLYCON_DECLARE(s3c2440, "samsung,s3c2440-uart",
+			s3c2440_early_console_setup);
+OF_EARLYCON_DECLARE(s3c6400, "samsung,s3c6400-uart",
+			s3c2440_early_console_setup);
+EARLYCON_DECLARE(s3c2412, s3c2440_early_console_setup);
+EARLYCON_DECLARE(s3c2440, s3c2440_early_console_setup);
+EARLYCON_DECLARE(s3c6400, s3c2440_early_console_setup);
+
+/* S5PV210, EXYNOS */
+static struct samsung_early_console_data s5pv210_early_console_data = {
+	.txfull_mask = S5PV210_UFSTAT_TXFULL,
+};
+
+static int __init s5pv210_early_console_setup(struct earlycon_device *device,
+					      const char *opt)
+{
+	device->port.private_data = &s5pv210_early_console_data;
+	return samsung_early_console_setup(device, opt);
+}
+OF_EARLYCON_DECLARE(s5pv210, "samsung,s5pv210-uart",
+			s5pv210_early_console_setup);
+OF_EARLYCON_DECLARE(exynos4210, "samsung,exynos4210-uart",
+			s5pv210_early_console_setup);
+EARLYCON_DECLARE(s5pv210, s5pv210_early_console_setup);
+EARLYCON_DECLARE(exynos4210, s5pv210_early_console_setup);
+
 MODULE_ALIAS("platform:samsung-uart");
 MODULE_DESCRIPTION("Samsung SoC Serial port driver");
 MODULE_AUTHOR("Ben Dooks <ben@simtec.co.uk>");