linux-kernel - Re: [Intel-gfx] [PATCH] iommu: export no_iommu and dmar

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Message-ID: <86aa7mefak.fsf@sumi.keithp.com>
Date:	Wed, 23 Nov 2011 12:48:19 -0800
From:	Keith Packard <keithp@...thp.com>
To:	David Woodhouse <dwmw2@...radead.org>,
	Eugeni Dodonov <eugeni.dodonov@...el.com>
Cc:	Daniel Vetter <daniel.vetter@...ll.ch>,
	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] iommu: export no_iommu and dmar_disabled symbols

On Wed, 23 Nov 2011 20:36:00 +0000, David Woodhouse <dwmw2@...radead.org> wrote:

> This is horrid. In the general case, drivers have no business knowing
> this. We need to properly identify what is wrong with this hardware, and
> put in a quirk for it — perhaps refusing to enable the IOMMU at all on
> the broken chipsets.

That'd be fine with me, right now we're disabling RC6 and semaphores --
semaphores aren't all that important, although they do improve
performance a bit. RC6 is important, saving a huge amount of power.

I'd also be OK with requiring special options to enable DMAR and having
that also disable RC6/semaphores, if you'd rather expose that. In either
case, we need something that works and avoids hanging machines.

-- 
keith.packard@...el.com

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