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Date:      Sun, 30 May 1999 16:33:33 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        roger@cs.strath.ac.uk (Roger Hardiman)
Subject:   Re: PCI bus chanages from 2.2.x to 3.x/4.x and data corruption.
Message-ID:  <199905301433.QAA16916@labinfo.iet.unipi.it>
In-Reply-To: <37516241.9DA2276@cs.strath.ac.uk> from "Roger Hardiman" at May 30, 99 05:07:10 pm

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> AAAH, In that case I may know the bug!!!!
> 
> It may be a compiler optimisation.

i think all memory-mapped registers should be declared "volatile" to
avoid such things occur. I remember when i was looking at both the
meteor and bt848 drivers, there was some confusion about it.

however looking at the source code, it seems declaration are ok:

in brktree_reg.h:

typedef volatile u_int  bregister_t;    
#define BTBYTE(what)    bregister_t  what:8; int :24
	...
	BTBYTE (tdec);              /* 8, 9,a,b */


I think we should look at the .o file ...

	cheers
	luigi


-----------------------------------+-------------------------------------
  Luigi RIZZO, luigi@iet.unipi.it  . Dip. di Ing. dell'Informazione
  http://www.iet.unipi.it/~luigi/  . Universita` di Pisa
  TEL/FAX: +39-050-568.533/522     . via Diotisalvi 2, 56126 PISA (Italy)

		  http://www.iet.unipi.it/~luigi/ngc99/
====  First International Workshop on Networked Group Communication  ====
-----------------------------------+-------------------------------------

> I helped someone recently, I think a BSDI user, whose PC would hang.
> When you set the TDEC register (for the FPS), you have to set it to zero
> first.
> 
> Someone was getting actual hangs of their PC and narrowed it down to the
> FPS
> code.
> 
> The code is
> {
> ..... blah blah blah - c code
> set tdec to 0
> set tdec to desired value
> ..... blah blah blah - c code
> }
> 
> We changed this to
> {
> set tdec to 0
> ..... blah blah blah - c code
> set tdec to desired value
> ..... blah blah blah - c code
> }
> 


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