Prev: [PATCH] Typo in drivers/base/core.c
Next: Typo in drivers/base/core.c
From: Robert Hancock on 17 May 2010 21:10
On Mon, May 17, 2010 at 7:02 PM, Linus Torvalds
<torvalds(a)linux-foundation.org> wrote:
>
>
> 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".

It sounds like this bug only affects HPET MSI requests (presumably the
only ones that the southbridge can concern itself with), not any
others. It would require the HPET code to support having its MSI
support yanked away at runtime, 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: Andi Kleen on 18 May 2010 04:50
> 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.

There can be LPC devices which are not visible to the kernel,
but only used through ACPI or the BIOS. Think of fancy fan
controllers and similar.

-Andi
--
ak(a)linux.intel.com -- Speaking for myself only.
--
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 18 May 2010 19:30
On Tue, May 18, 2010 at 2:45 AM, Andi Kleen <andi(a)firstfloor.org> 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.
>
> There can be LPC devices which are not visible to the kernel,
> but only used through ACPI or the BIOS. Think of fancy fan
> controllers and similar.

I would hope they wouldn't use DMA without kernel knowledge, otherwise
that really would be an abomination..
--
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/
First  |  Prev  | 
Pages: 1 2
Prev: [PATCH] Typo in drivers/base/core.c
Next: Typo in drivers/base/core.c