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 Original line 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

			determined by the stdout-path property in device

			tree's chosen node.

			tree's chosen node.





		cdns,<addr>

		cdns,<addr>[,options]

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

			Start an early, polled-mode console on a Cadence

			port at the specified address. The cadence serial port

			(xuartps) serial port at the specified address. Only

			must already be setup and configured. Options are not

			supported option is baud rate. If baud rate is not

			yet supported.

			specified, the serial port must already be setup and

			configured.





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

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

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

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

drivers/tty/serial/xilinx_uartps.c

+26 −1
Original line number Original line 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,

static int __init cdns_early_console_setup(struct earlycon_device *device,

					   const char *opt)

					   const char *opt)

{

{

	if (!device->port.membase)

	struct uart_port *port = &device->port;



	if (!port->membase)

		return -ENODEV;

		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;

	device->con->write = cdns_early_write;





	return 0;

	return 0;