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tty/serial: pl011: add generic earlycon support

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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>
This commit is contained in:
Rob Herring 2014-04-18 17:19:57 -05:00 committed by Greg Kroah-Hartman
parent d2fd6810a8
commit 0d3c673e78
3 changed files with 37 additions and 1 deletions
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7
Documentation/kernel-parameters.txt
View file

@ -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

1
drivers/tty/serial/Kconfig
View file

@ -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

30
drivers/tty/serial/amba-pl011.c
View file

@ -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