x86: Disable HPET MSI on ATI SB700/SB800
in [Kernel]
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From: Andreas Herrmann on 17 May 2010 11:10 On Mon, Jan 25, 2010 at 06:10:59PM +0100, Andreas Herrmann wrote: > On Fri, Jan 22, 2010 at 11:21:06PM -0800, Yuhong Bao wrote: > > > > > HPET MSI on platforms with ATI SB700/SB800 as they seem to have some > > > side-effects on floppy DMA. Do not use HPET MSI on such platforms. > > Argh, will see what information I can find about this problem ... FYI. I've tried to trigger the publication of errata information for that chipset. Finally this has happened. The discussed problem is indeed due to an erratum. See erratum #27 in http://support.amd.com/us/Embedded_TechDocs/46837.pdf The suggested workaround for this is to disable HPET MSI if LPC devices are used. I doubt that there is a convenient way for Linux to find out whether LPC devices are used. Thus I think the only solution to safely avoid the problem is the currently implemented quirk to disable HPET MSI on this chipset. Regards, Andreas -- Operating | Advanced Micro Devices GmbH System | Einsteinring 24, 85609 Dornach b. M�nchen, Germany Research | Gesch�ftsf�hrer: Andrew Bowd, Thomas M. McCoy, Giuliano Meroni Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis M�nchen (OSRC) | Registergericht M�nchen, HRB Nr. 43632 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Yuhong Bao on 17 May 2010 11:20 > The suggested workaround for this is to disable HPET MSI if LPC > devices are used. I doubt that there is a convenient way for Linux to > find out whether LPC devices are used.And don't forget that the Super I/O chip in most motherboards is an LPC device!(In fact, that was what LPC was invented for) > Thus I think the only solution > to safely avoid the problem is the currently implemented quirk to > disable HPET MSI on this chipset. Yuhong Bao _________________________________________________________________ The New Busy is not the too busy. Combine all your e-mail accounts with Hotmail. http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_4-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Linus Torvalds on 17 May 2010 11:20 On Mon, 17 May 2010, Andreas Herrmann wrote: > > FYI. I've tried to trigger the publication of errata information for that > chipset. Finally this has happened. > > The discussed problem is indeed due to an erratum. See erratum #27 in > http://support.amd.com/us/Embedded_TechDocs/46837.pdf > > The suggested workaround for this is to disable HPET MSI if LPC > devices are used. I doubt that there is a convenient way for Linux to > find out whether LPC devices are used. Thus I think the only solution > to safely avoid the problem is the currently implemented quirk to > disable HPET MSI on this chipset. Goodie. It would be good to point this out in the source too. Would you be willing to send in a patch that documents this quirk as a result of that erratum #27, so that we don't lose sight of why we're doing that odd MSI disable? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Robert Hancock on 17 May 2010 21:00 On 05/17/2010 08:59 AM, Andreas Herrmann wrote: > On Mon, Jan 25, 2010 at 06:10:59PM +0100, Andreas Herrmann wrote: >> On Fri, Jan 22, 2010 at 11:21:06PM -0800, Yuhong Bao wrote: >>> >>>> HPET MSI on platforms with ATI SB700/SB800 as they seem to have some >>>> side-effects on floppy DMA. Do not use HPET MSI on such platforms. >> >> Argh, will see what information I can find about this problem ... > > FYI. I've tried to trigger the publication of errata information for that > chipset. Finally this has happened. > > The discussed problem is indeed due to an erratum. See erratum #27 in > http://support.amd.com/us/Embedded_TechDocs/46837.pdf > > The suggested workaround for this is to disable HPET MSI if LPC > devices are used. I doubt that there is a convenient way for Linux to > find out whether LPC devices are used. Thus I think the only solution > to safely avoid the problem is the currently implemented quirk to > disable HPET MSI on this chipset. If one wanted, you could disable HPET MSI on this chipset only when a driver requests an ISA DMA channel. Then if there's no floppy or other LPC DMA device present, it can stay enabled. I don't know if it's worth the trouble, though. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Linus Torvalds on 17 May 2010 21:10
On Mon, 17 May 2010, Robert Hancock wrote: > > If one wanted, you could disable HPET MSI on this chipset only when a driver > requests an ISA DMA channel. Then if there's no floppy or other LPC DMA device > present, it can stay enabled. I don't know if it's worth the trouble, though. Nope, that wouldn't work. Imagine a driver that already loaded, and is already using MSI (say, network device). What happens now if you want to access the floppy and load the floppy module? Oh, you can't? Need to bring down the network interface, unload that module first? Not practical. Sure, in theory we can do some crazy callback for "you now need to re-do your interrupt registration" for all devices. In practice, I can onyl say "not going to happen". Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |