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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: Scott Telford <stelford@cadence.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Scott Telford 2016-09-22 16:58:16 +01:00 committed by Greg Kroah-Hartman
parent 212d249b6a
commit c41251b175
2 changed files with 32 additions and 6 deletions
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11
Documentation/kernel-parameters.txt
View File

@ -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]

27
drivers/tty/serial/xilinx_uartps.c
View File

@ -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;