Message-ID: <407239DB.1010600@maptek.com.au>
Date: Tue, 06 Apr 2004 14:32:19 +0930
From: Malcolm Blaney <malcolm.blaney@maptek.com.au>
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To: lkml <linux-kernel@vger.kernel.org>
Subject: Re: mark_offset_tsc() hangs usb
References: <406BA62A.2090503@maptek.com.au>
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I wrote:

> I have been trying to fix a problem related to usb, with the help of the 
> usb-dev list. Plugging in a usb device hangs my computer when bandwidth 
> reclamation (fsbr) is turned on in the uhci-hcd driver.
> 
> I have found though, that when an interrupt is triggered by plugging in 
> a usb device, the timer_interrupt() function in arch/i386/kernel/time.c 
> is reached, and the computer hangs in mark_offset_tsc() in 
> timers/timer_tsc.c. I removed the call to this function in 
> timer_interrupt() and then usb worked as normal. I'm hoping there's a 
> better way to get usb working than this though! This doesn't happen when 
> fsbr is switched off.
> 
> The computer has a Crusoe TM5400 cpu and a VIA VT82C686A controller.

I've been trying to work out what goes wrong in mark_offset_tsc() and 
found that it's just the outb_p() & inb_p() calls that are causing the 
problem. I found a thread relating to this, 
http://www.ussg.iu.edu/hypermail/linux/kernel/0309.2/1039.html, and 
tried the line:
#define __SLOW_DOWN_IO__ ""
which also allowed usb to work normally. Since this is just avoiding the 
read or write to port 0x80, is this a sign of having dodgy hardware? The 
thread doesn't talk about writing to the port as being fatal, even if it 
does cause problems for some people.

Anybody got a better fix?

Malcolm.

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