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drm/i915: fix rc6 initialization on Ironlake 

There is a race condition between setting PWRCTXA and executing
MI_SET_CONTEXT. PWRCTXA must not be set until a valid context has been
written (or else the GPU could possible go into rc6, and return to an
invalid context).

Reported-and-Tested-by: Gu Rui <chaos.proton@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=28582
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Ben Widawsky 2011-03-19 18:14:28 -07:00 committed by Keith Packard
parent 96f298aa9c
commit 4a246cfc3c
1 changed files with 13 additions and 0 deletions
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13
drivers/gpu/drm/i915/intel_display.c
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@ -7325,6 +7325,19 @@ void ironlake_enable_rc6(struct drm_device *dev)
OUT_RING(MI_FLUSH);
ADVANCE_LP_RING();
/*
* Wait for the command parser to advance past MI_SET_CONTEXT. The HW
* does an implicit flush, combined with MI_FLUSH above, it should be
* safe to assume that renderctx is valid
*/
ret = intel_wait_ring_idle(LP_RING(dev_priv));
if (ret) {
DRM_ERROR("failed to enable ironlake power power savings\n");
ironlake_teardown_rc6(dev);
mutex_unlock(&dev->struct_mutex);
return;
}
I915_WRITE(PWRCTXA, dev_priv->pwrctx->gtt_offset | PWRCTX_EN);
I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) & ~RCX_SW_EXIT);
mutex_unlock(&dev->struct_mutex);