[CFT] Serial double initialisation

[CFT] Serial double initialisation

[Russell King]

A while ago, Alan reported to me a double-initialisation bug between the
ISA init and PNP initialisation of serial ports.

Since then, Alan integrated a patch I sent him into -ac, and as yet I
haven't heard any feedback.  Since I don't have the PNP hardware to be
able to test this, I'm not putting it into Linus' tree until I hear some
success.

So, if people are using 2.5.50 with PNP support enabled, and if you are
seeing two "ttyS0" lines during the kernel boot messages, please apply
this patch and confirm to me that it correctly reports one ttyS0 message.

This is the exact same patch I sent to Alan, and appears to apply cleanly
to the current 2.5.50 BK tree.

Hopefully looking forward to some feedback.

Thanks.

--- orig/drivers/serial/core.c	Tue Nov  5 12:51:26 2002
+++ linux/drivers/serial/core.c	Mon Nov 25 11:44:08 2002
@@ -2405,17 +2405,22 @@
 			goto out;
 		}
 
-		state->port->iobase   = port->iobase;
-		state->port->membase  = port->membase;
-		state->port->irq      = port->irq;
-		state->port->uartclk  = port->uartclk;
-		state->port->fifosize = port->fifosize;
-		state->port->regshift = port->regshift;
-		state->port->iotype   = port->iotype;
-		state->port->flags    = port->flags;
-		state->port->line     = state - drv->state;
+		/*
+		 * If the port is already initialised, don't touch it.
+		 */
+		if (state->port->type == PORT_UNKNOWN) {
+			state->port->iobase   = port->iobase;
+			state->port->membase  = port->membase;
+			state->port->irq      = port->irq;
+			state->port->uartclk  = port->uartclk;
+			state->port->fifosize = port->fifosize;
+			state->port->regshift = port->regshift;
+			state->port->iotype   = port->iotype;
+			state->port->flags    = port->flags;
+			state->port->line     = state - drv->state;
 
-		__uart_register_port(drv, state, state->port);
+			__uart_register_port(drv, state, state->port);
+		}
 
 		ret = state->port->line;
 	} else


-- 
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html

Re: [CFT] Serial double initialisation

[Zwane Mwaikambo]

On Sat, 30 Nov 2002, Russell King wrote:

> A while ago, Alan reported to me a double-initialisation bug between the
> ISA init and PNP initialisation of serial ports.
>
> Since then, Alan integrated a patch I sent him into -ac, and as yet I
> haven't heard any feedback.  Since I don't have the PNP hardware to be
> able to test this, I'm not putting it into Linus' tree until I hear some
> success.
>
> So, if people are using 2.5.50 with PNP support enabled, and if you are
> seeing two "ttyS0" lines during the kernel boot messages, please apply
> this patch and confirm to me that it correctly reports one ttyS0 message.

Thanks for checking this out, the double init only comes when you have
CONFIG_PNPBIOS enabled, but CONFIG_ISAPNP alone is fine. I tested the
patch with both and it does indeed fix the problem.

Cheers,
	Zwane

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