Date: Fri, 26 Feb 2010 13:50:35 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Larry Finger <Larry.Finger@lwfinger.net>
cc: =?ISO-8859-15?Q?G=E1bor_Stefanik?= <netrolller.3d@gmail.com>,
	"John W. Linville" <linville@tuxdriver.com>,
	"David S. Miller" <davem@davemloft.net>,
	wireless <linux-wireless@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@suse.de>
Subject: Re: Make b43 driver fall back gracefully to PIO mode after fatal
 DMA  errors
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On Fri, 26 Feb 2010, Linus Torvalds wrote:
> 
> so even if mmiotrace fixes it for others, it's not working for me.

Side note: In case this is timing-related: the machine in question is a 
dual-core 1.3Ghz CPU (Core 2 Duo U1400). I think SMP has always been 
enabled, I don't think I ever tried UP.

Also, in addition to the PIO fallback code, that particular mmiotrace test 
was done with the "udelay(10)" added to the b43_write*() functions. So it 
was even slower.

Maybe the bug only happens on slow machines (and then the udelay obviously 
wouldn't help!), but that would not explain why mmiotrace might then 
_hide_ the bug for some people.

			Linus