linux-kernel - Re: [PATCH] drm/i915: By default, enable RC6 on IVB and SNB when reasonable

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Message-ID: <86aa7sklos.fsf@sumi.keithp.com>
Date:	Sat, 19 Nov 2011 10:32:19 -0800
From:	Keith Packard <keithp@...thp.com>
To:	Eugeni Dodonov <eugeni@...onov.net>
Cc:	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/i915: By default, enable RC6 on IVB and SNB when reasonable

On Sat, 19 Nov 2011 07:25:09 -0200, Eugeni Dodonov <eugeni@...onov.net> wrote:

> Just one question I caught on 2nd read. Shouldn't we have #else within
> this #ifdef block, to return 1? Otherwise, if CONFIG_INTEL_IOMMU is
> not defined, we'll always disable rc6.

Oops! Thanks for catching this. Here's a new version of that function
(the rest of the patch is the same). This one has explicit conditions
for Ironlake and Sandybridge (when CONFIG_INTEL_IOMMU is set), allowing
the Ivybridge and Sandybridge-without-IOMMU cases to take the default
path. This will also cause all future chips to enable rc6 by default.
 
+static bool intel_enable_rc6(struct drm_device *dev)
+{
+	/*
+	 * Respect the kernel parameter if it is set
+	 */
+	if (i915_enable_rc6 >= 0)
+		return i915_enable_rc6;
+
+	/*
+	 * Disable RC6 on Ironlake
+	 */
+	if (INTEL_INFO(dev)->gen == 5)
+		return 0;
+
+#ifdef CONFIG_INTEL_IOMMU
+	/*
+	 * Enable rc6 on Sandybridge if DMA remapping is disabled
+	 */
+	if (INTEL_INFO(dev)->gen == 6)
+		return no_iommu || dmar_disabled;
+#endif
+	return 1;
+}
+

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

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