[PATCH,resend] don't disable xscale serial ports after autoconfig

[PATCH,resend] don't disable xscale serial ports after autoconfig

[Lennert Buytenhek]

(please CC, not on the list)

Hi,

xscale-type UARTs have an extra bit (UUE) in the IER register that has
to be written as 1 to enable the UART.  At the end of autoconfig() in
drivers/serial/8250.c, the IER register is unconditionally written as
zero, which turns off the UART, and makes any subsequent printch() hang
the box.

Since other 8250-type UARTs don't have this enable bit and are thus
always 'enabled' in this sense, it can't hurt to enable xscale-type
serial ports all the time as well.  The attached patch changes the
autoconfig() exit path to see if the port has an UUE enable bit, and if
yes, to write UUE=1 instead of just putting a zero into IER, using the
same test as is used at the beginning of serial8250_console_write().


cheers,
Lennert

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>

diff -urN linux-2.6.13.orig/drivers/serial/8250.c linux-2.6.13/drivers/serial/8250.c
--- linux-2.6.13.orig/drivers/serial/8250.c	2005-08-29 01:41:01.000000000 +0200
+++ linux-2.6.13/drivers/serial/8250.c	2005-10-02 21:38:51.000000000 +0200
@@ -936,7 +936,10 @@
 	serial_outp(up, UART_MCR, save_mcr);
 	serial8250_clear_fifos(up);
 	(void)serial_in(up, UART_RX);
-	serial_outp(up, UART_IER, 0);
+	if (up->capabilities & UART_CAP_UUE)
+		serial_outp(up, UART_IER, UART_IER_UUE);
+	else
+		serial_outp(up, UART_IER, 0);
 
  out:	
 	spin_unlock_irqrestore(&up->port.lock, flags);

Re: [PATCH,resend] don't disable xscale serial ports after autoconfig

[Russell King]

On Sun, Oct 30, 2005 at 02:42:09PM +0100, Lennert Buytenhek wrote:
> xscale-type UARTs have an extra bit (UUE) in the IER register that has
> to be written as 1 to enable the UART.  At the end of autoconfig() in
> drivers/serial/8250.c, the IER register is unconditionally written as
> zero, which turns off the UART, and makes any subsequent printch() hang
> the box.

Applied, thanks.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core