static unsigned int __init probe_baud(struct uart_port *port)
{
unsigned char lcr, dll, dlm;
unsigned int quot;
lcr = serial8250_early_in(port, UART_LCR);
serial8250_early_out(port, UART_LCR, lcr | UART_LCR_DLAB);
dll = serial8250_early_in(port, UART_DLL);
dlm = serial8250_early_in(port, UART_DLM);
serial8250_early_out(port, UART_LCR, lcr);
quot = (dlm << 8) | dll;
return (port->uartclk / 16) / quot;
}
static void __init wait_for_xmitr(struct uart_port *port)
{
unsigned int status;
for (;;) {
status = serial8250_early_in(port, UART_LSR);
if ((status & BOTH_EMPTY) == BOTH_EMPTY)
return;
cpu_relax();
}
}
static void __init init_port(struct earlycon_device *device)
{
struct uart_port *port = &device->port;
unsigned int divisor;
unsigned char c;
unsigned int ier;
serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */
ier = serial8250_early_in(port, UART_IER);
serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
serial8250_early_out(port, UART_FCR, 0); /* no fifo */
serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */
divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
c = serial8250_early_in(port, UART_LCR);
serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
serial8250_early_out(port, UART_DLL, divisor & 0xff);
serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
}
static void __init early_serial8250_write(struct console *console,
const char *s, unsigned int count)
{
struct uart_port *port = &early_device.port;
unsigned int ier;
/* Save the IER and disable interrupts */
ier = serial8250_early_in(port, UART_IER);
serial8250_early_out(port, UART_IER, 0);
uart_console_write(port, s, count, serial_putc);
/* Wait for transmitter to become empty and restore the IER */
wait_for_xmitr(port);
serial8250_early_out(port, UART_IER, ier);
}