serial: altera_uart: add earlycon support

Nios2 currently uses its own early printk implementation, rather than
using unified earlycon support to show boot messages on altera_uart.

Add earlycon support to altera_uart so that other archs may use it.
Also, this (together with the corresponding patch for altera_jtaguart)
will allow the early printk implementation in arch/nios2 to be removed
in a future patch.

Cc: Ley Foon Tan <lftan@altera.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 896f5eb78da0e133c9d04714588343957450b400..5c8850f7a2a05a252ccf4762f1b594fd67697877 100644 (file)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1392,6 +1392,7 @@ config SERIAL_ALTERA_UART_CONSOLE
        bool "Altera UART console support"
        depends on SERIAL_ALTERA_UART=y
        select SERIAL_CORE_CONSOLE
+       select SERIAL_EARLYCON
        help
          Enable a Altera UART port to be the system console.
 

diff --git a/drivers/tty/serial/altera_uart.c b/drivers/tty/serial/altera_uart.c
index 820a74208696bf57b275542ef810663c6ea175b7..46d3438a0d27014ce97115e7a17b0eb024f12035 100644 (file)
--- a/drivers/tty/serial/altera_uart.c
+++ b/drivers/tty/serial/altera_uart.c
@@ -489,6 +489,38 @@ console_initcall(altera_uart_console_init);
 
 #define        ALTERA_UART_CONSOLE     (&altera_uart_console)
 
+static void altera_uart_earlycon_write(struct console *co, const char *s,
+                                      unsigned int count)
+{
+       struct earlycon_device *dev = co->data;
+
+       uart_console_write(&dev->port, s, count, altera_uart_console_putc);
+}
+
+static int __init altera_uart_earlycon_setup(struct earlycon_device *dev,
+                                            const char *options)
+{
+       struct uart_port *port = &dev->port;
+
+       if (!port->membase)
+               return -ENODEV;
+
+       /* Enable RX interrupts now */
+       writel(ALTERA_UART_CONTROL_RRDY_MSK,
+              port->membase + ALTERA_UART_CONTROL_REG);
+
+       if (dev->baud) {
+               unsigned int baudclk = port->uartclk / dev->baud;
+
+               writel(baudclk, port->membase + ALTERA_UART_DIVISOR_REG);
+       }
+
+       dev->con->write = altera_uart_earlycon_write;
+       return 0;
+}
+
+OF_EARLYCON_DECLARE(uart, "altr,uart-1.0", altera_uart_earlycon_setup);
+
 #else
 
 #define        ALTERA_UART_CONSOLE     NULL