Chris Wilson bcf9dcc1e6 drm/i915: Workaround hang with BSD and forcewake on SandyBridge ... For reasons that are not apparent to anybody, 990bbdadab (drm/i915: Group the GT routines together in both code and vtable) breaks the use of the BitStream Decoder ring on SandyBridge. The active ingredient of that patch is the conversion from a udelay(10) to a udelay(1) in the busy-wait loop of waiting for the forcewake acknowledge. If we restore that udelay(10) or insert another udelay(1) afterwards (or any wait longer than 250ns) everything works again. An alternative is also to remove any delay from the busy-wait loop. Given that in the atomic sections we want to complete the wait as quick as possible to avoid blocking the CPU for too long, it makes sense to remove the delay altogether and simply spin on the exit condition until it completes. So we replace the udelay(1) with cpu_relax(). Papers over regression from commit 990bbdadab Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Mon Jul 2 11:51:02 2012 -0300 drm/i915: Group the GT routines together in both code and vtable Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51738 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>		2012-08-06 10:43:29 +02:00
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drm	drm/i915: Workaround hang with BSD and forcewake on SandyBridge	2012-08-06 10:43:29 +02:00
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vga	vga_switcheroo: Enable/disable audio clients at the right time	2012-06-09 12:14:43 +02:00
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