tty/serial: pl011: add generic earlycon support

Add earlycon support for the pl011 serial port. This allows enabling
the pl011 for console when early_params are processed. This is based
on the arm64 earlyprintk support and is intended to replace it.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 29 insertions, 1 deletions

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index dacf0a09ab24..ee3d80346780 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -303,7 +303,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *
 
         /* Optionally make use of an RX channel as well */
         chan = dma_request_slave_channel(dev, "rx");
-        
+
         if (!chan && plat->dma_rx_param) {
                 chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);
 
@@ -2045,6 +2045,34 @@ static struct console amba_console = {
 };
 
 #define AMBA_CONSOLE    (&amba_console)
+
+static void pl011_putc(struct uart_port *port, int c)
+{
+        while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF)
+                ;
+        writeb(c, port->membase + UART01x_DR);
+        while (readl(port->membase + UART01x_FR) & UART01x_FR_BUSY)
+                ;
+}
+
+static void pl011_early_write(struct console *con, const char *s, unsigned n)
+{
+        struct earlycon_device *dev = con->data;
+
+        uart_console_write(&dev->port, s, n, pl011_putc);
+}
+
+static int __init pl011_early_console_setup(struct earlycon_device *device,
+                                            const char *opt)
+{
+        if (!device->port.membase)
+                return -ENODEV;
+
+        device->con->write = pl011_early_write;
+        return 0;
+}
+EARLYCON_DECLARE(pl011, pl011_early_console_setup);
+
 #else
 #define AMBA_CONSOLE    NULL
 #endif