serial: omap: Add omapserial earlycon

Add DT earlycon for omap_serial driver. This boot console is included
with CONFIG_SERIAL_EARLYCON=y, CONFIG_OF=y, CONFIG_SERIAL_OMAP=y, and
CONFIG_OF_EARLY_FLATTREE=y.

This boot console is enabled with the command line option "earlycon"
(without "=<name>...") when the DT 'stdout-path' property matches a
compatible uart.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index a2a5299..3bbc4b5 100644 (file)
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1234,6 +1234,61 @@ out:
 
 #ifdef CONFIG_SERIAL_OMAP_CONSOLE
 
+#ifdef CONFIG_SERIAL_EARLYCON
+static unsigned int __init omap_serial_early_in(struct uart_port *port,
+                                               int offset)
+{
+       offset <<= port->regshift;
+       return readw(port->membase + offset);
+}
+
+static void __init omap_serial_early_out(struct uart_port *port, int offset,
+                                        int value)
+{
+       offset <<= port->regshift;
+       writew(value, port->membase + offset);
+}
+
+static void __init omap_serial_early_putc(struct uart_port *port, int c)
+{
+       unsigned int status;
+
+       for (;;) {
+               status = omap_serial_early_in(port, UART_LSR);
+               if ((status & BOTH_EMPTY) == BOTH_EMPTY)
+                       break;
+               cpu_relax();
+       }
+       omap_serial_early_out(port, UART_TX, c);
+}
+
+static void __init early_omap_serial_write(struct console *console,
+                                          const char *s, unsigned int count)
+{
+       struct earlycon_device *device = console->data;
+       struct uart_port *port = &device->port;
+
+       uart_console_write(port, s, count, omap_serial_early_putc);
+}
+
+static int __init early_omap_serial_setup(struct earlycon_device *device,
+                                         const char *options)
+{
+       struct uart_port *port = &device->port;
+
+       if (!(device->port.membase || device->port.iobase))
+               return -ENODEV;
+
+       port->regshift = 2;
+       device->con->write = early_omap_serial_write;
+       return 0;
+}
+
+OF_EARLYCON_DECLARE(omapserial, "ti,omap2-uart", early_omap_serial_setup);
+OF_EARLYCON_DECLARE(omapserial, "ti,omap3-uart", early_omap_serial_setup);
+OF_EARLYCON_DECLARE(omapserial, "ti,omap4-uart", early_omap_serial_setup);
+#endif /* CONFIG_SERIAL_EARLYCON */
+
 static struct uart_omap_port *serial_omap_console_ports[OMAP_MAX_HSUART_PORTS];
 
 static struct uart_driver serial_omap_reg;