From 7cdcc29e4919dc31f494eaf05e46005c28efe832 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Fri, 8 Jan 2016 15:34:05 -0500 Subject: serial-uartlite: add earlycon support Microblaze currently uses the old earlyprintk system, rather than the unified earlycon support, to show boot messages on uartlite. Add earlycon support so that other archs using uartlite can benefit from it. The new code in uartlite.c is copied almost verbatim from arch/microblaze/kernel/early_printk.c. Signed-off-by: Rich Felker Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/uartlite.c | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) (limited to 'drivers/tty/serial/uartlite.c') diff --git a/drivers/tty/serial/uartlite.c b/drivers/tty/serial/uartlite.c index b1c6bd3d483f..c249aee887d2 100644 --- a/drivers/tty/serial/uartlite.c +++ b/drivers/tty/serial/uartlite.c @@ -519,6 +519,47 @@ static int __init ulite_console_init(void) console_initcall(ulite_console_init); +static void early_uartlite_putc(struct uart_port *port, int c) +{ + /* + * Limit how many times we'll spin waiting for TX FIFO status. + * This will prevent lockups if the base address is incorrectly + * set, or any other issue on the UARTLITE. + * This limit is pretty arbitrary, unless we are at about 10 baud + * we'll never timeout on a working UART. + */ + + unsigned retries = 1000000; + /* read status bit - 0x8 offset */ + while (--retries && (readl(port->membase + 8) & (1 << 3))) + ; + + /* Only attempt the iowrite if we didn't timeout */ + /* write to TX_FIFO - 0x4 offset */ + if (retries) + writel(c & 0xff, port->membase + 4); +} + +static void early_uartlite_write(struct console *console, + const char *s, unsigned n) +{ + struct earlycon_device *device = console->data; + uart_console_write(&device->port, s, n, early_uartlite_putc); +} + +static int __init early_uartlite_setup(struct earlycon_device *device, + const char *options) +{ + if (!device->port.membase) + return -ENODEV; + + device->con->write = early_uartlite_write; + return 0; +} +EARLYCON_DECLARE(uartlite, early_uartlite_setup); +OF_EARLYCON_DECLARE(uartlite_b, "xlnx,opb-uartlite-1.00.b", early_uartlite_setup); +OF_EARLYCON_DECLARE(uartlite_a, "xlnx,xps-uartlite-1.00.a", early_uartlite_setup); + #endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */ static struct uart_driver ulite_uart_driver = { -- cgit v1.2.1