Subject: Re: Serial issue
From: Lee Revell <rlrevell@joe-job.com>
To: Paul Fulghum <paulkf@microgate.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
       Russell King <rmk+lkml@arm.linux.org.uk>
In-Reply-To: <1155915851.3426.4.camel@amdx2.microgate.com>
References: <1155862076.24907.5.camel@mindpipe>
	 <1155915851.3426.4.camel@amdx2.microgate.com>
Content-Type: text/plain
Date: Fri, 18 Aug 2006 13:55:33 -0400
Message-Id: <1155923734.2924.16.camel@mindpipe>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1817
Lines: 53

On Fri, 2006-08-18 at 10:44 -0500, Paul Fulghum wrote:
> On Thu, 2006-08-17 at 20:47 -0400, Lee Revell wrote:
> > I've found a weird serial bug.  My host is a Via EPIA M-6000 running
> > 2.6.17 connected to a PPC Yosemite board running 2.6.13. 
> > 
> > In all cases the serial console works great.  But, with the default
> > setting of IRQ 4, Kermit file transfers via the serial interface simply
> > time out.  However if I use polling mode (setserial /dev/ttyS0 irq 0 on
> > the host), file transfers work.
> > 
> > When set to IRQ 4, the interrupt count does increase.
> > 
> > # cat /proc/tty/driver/serial 
> > serinfo:1.0 driver revision:
> > 0: uart:16550A port:000003F8 irq:4 tx:267 rx:667 DSR|CD
> > [...]
> > 
> > Any ideas?  I'm guessing it might be a quirk of the VIA chipset?
> 
> You mention serial console. Hasn't there been some changes
> related to reenabling the THRE interrupt after sending
> console data? IIRC the changes fixed transmit stalls on
> some machines but broke things on other machine.

I tried Paul's suggestion:

--- drivers/serial/8250.c~	2006-06-17 21:49:35.000000000 -0400
+++ drivers/serial/8250.c	2006-08-18 12:57:16.000000000 -0400
@@ -2263,7 +2263,7 @@
 	 *	and restore the IER
 	 */
 	wait_for_xmitr(up, BOTH_EMPTY);
-	serial_out(up, UART_IER, ier);
+	serial_out(up, UART_IER, ier | UART_IER_THRI);
 
 	if (locked)
 		spin_unlock_irqrestore(&up->port.lock, flags);


But it had no effect.

Could it be a hardware-specific bug?  After all VIA chipsets are
notorious for interrupts not working right.

Any other suggestions?

Lee

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/