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Commit c41251b1 authored by Scott Telford's avatar Scott Telford Committed by Greg Kroah-Hartman
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serial: xuartps: Add some register initialisation to cdns_early_console_setup() 



Add initialisation of control register and baud rate to
cdns_early_console_setup(), required when running kernel standalone
without a boot loader. Baud rate is only initialised when specified in
earlycon command-line option, otherwise it is assumed this has been
set by a boot loader. Updated Documentation/kernel-parameters.txt
accordingly.

Signed-off-by: default avatarScott Telford <stelford@cadence.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 212d249b

Documentation/kernel-parameters.txt

+6 −5
Original line number Diff line number Diff line
@@ -1045,11 +1045,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			determined by the stdout-path property in device

			tree's chosen node.



		cdns,<addr>

			Start an early, polled-mode console on a cadence serial

			port at the specified address. The cadence serial port

			must already be setup and configured. Options are not

			yet supported.

		cdns,<addr>[,options]

			Start an early, polled-mode console on a Cadence

			(xuartps) serial port at the specified address. Only

			supported option is baud rate. If baud rate is not

			specified, the serial port must already be setup and

			configured.



		uart[8250],io,<addr>[,options]

		uart[8250],mmio,<addr>[,options]

drivers/tty/serial/xilinx_uartps.c

+26 −1
Original line number Diff line number Diff line
@@ -1165,9 +1165,34 @@ static void __init cdns_early_write(struct console *con, const char *s, 
static int __init cdns_early_console_setup(struct earlycon_device *device,

					   const char *opt)

{

	if (!device->port.membase)

	struct uart_port *port = &device->port;



	if (!port->membase)

		return -ENODEV;



	/* initialise control register */

	writel(CDNS_UART_CR_TX_EN|CDNS_UART_CR_TXRST|CDNS_UART_CR_RXRST,

	       port->membase + CDNS_UART_CR);



	/* only set baud if specified on command line - otherwise

	 * assume it has been initialized by a boot loader.

	 */

	if (device->baud) {

		u32 cd = 0, bdiv = 0;

		u32 mr;

		int div8;



		cdns_uart_calc_baud_divs(port->uartclk, device->baud,

					 &bdiv, &cd, &div8);

		mr = CDNS_UART_MR_PARITY_NONE;

		if (div8)

			mr |= CDNS_UART_MR_CLKSEL;



		writel(mr,   port->membase + CDNS_UART_MR);

		writel(cd,   port->membase + CDNS_UART_BAUDGEN);

		writel(bdiv, port->membase + CDNS_UART_BAUDDIV);

	}



	device->con->write = cdns_early_write;



	return 0;