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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4384217..2609ead 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -883,6 +883,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        which are not unmapped.
 
        earlycon=       [KNL] Output early console device and options.
+
                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                uart[8250],mmio32,<addr>[,options]
@@ -892,6 +893,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        (mmio) or 32-bit (mmio32).
                        The options are the same as for ttyS, above.
 
+               pl011,<addr>
+                       Start an early, polled-mode console on a pl011 serial
+                       port at the specified address. The pl011 serial port
+                       must already be setup and configured. Options are not
+                       yet supported.
+
        earlyprintk=    [X86,SH,BLACKFIN,ARM]
                        earlyprintk=vga
                        earlyprintk=efi

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 9fb6028..4290d05 100644 (file)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -60,6 +60,7 @@ config SERIAL_AMBA_PL011_CONSOLE
        bool "Support for console on AMBA serial port"
        depends on SERIAL_AMBA_PL011=y
        select SERIAL_CORE_CONSOLE
+       select SERIAL_EARLYCON
        ---help---
          Say Y here if you wish to use an AMBA PrimeCell UART as the system
          console (the system console is the device which receives all kernel

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index dacf0a0..ee3d803 100644 (file)
--- 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