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Date: Sat, 15 Dec 2007 08:43:58 +0100 From: Ingo Molnar <mingo@...e.hu> To: "H. Peter Anvin" <hpa@...or.com> Cc: "David P. Reed" <dpreed@...d.com>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Rene Herman <rene.herman@...access.nl>, Pavel Machek <pavel@....cz> Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc. * H. Peter Anvin <hpa@...or.com> wrote: > I believe this will suffer from the issue that was raised: this will > use udelay() long before loop calibration (and no, we can't just "be > conservative" since there is no "conservative" value we can use.) > > Worse, I suspect that at least the PIT, which may need to be used for > udelay calibration, is one of the devices that may be affected. I > have seen the Verilog for a contemporary chipset, and it can only > access the PIT once per microsecond -- this actually has to do with > the definition of the PIT; some of the PIT operations are ill-defined > if allowed at a higher frequency than the PIT clock. i think the native_io_delay() in quirks.c signals the obvious solution: a DMI (or otherwise) driven quirk that activates a port 0x80 based delay on such boards. Combined with an iodelay=port80 boot option as well perhaps, just in case someone hits a system that is not blacklisted yet. This way such crazy broken hardware can be mapped correctly - like we map such quirks in every other case. Perhaps even do this workaround on the PIT driver level. Instead of perpetuating the superstition of port 80 forever. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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