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drm/i915: grab force_wake when restoring LCPLL

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If LCPLL is disabled, there's a chance we might be in package C8 state
or deeper, and we'll get a hard hang when restoring LCPLL (also, a red
led lights up on my motherboard). So grab the force_wake, which will
get us out of RC6 and, as a consequence, out of PC8+ (since we need
RC6 to get into PC8+).

Note: Discussions with hw designers are still ongoing what exactly
goes boom here. But I think we can go ahead and just merge this little
hack for now until it's clear what we actually need.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: Add small note about the current state of the discussion
around this hack.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Paulo Zanoni 2013-08-19 13:18:07 -03:00 committed by Daniel Vetter
parent 3414caf634
commit 215733fadb
1 changed files with 6 additions and 0 deletions
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6
drivers/gpu/drm/i915/intel_display.c
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@ -6033,6 +6033,10 @@ void hsw_restore_lcpll(struct drm_i915_private *dev_priv)
LCPLL_POWER_DOWN_ALLOW)) == LCPLL_PLL_LOCK)
return;
/* Make sure we're not on PC8 state before disabling PC8, otherwise
* we'll hang the machine! */
dev_priv->uncore.funcs.force_wake_get(dev_priv);
if (val & LCPLL_POWER_DOWN_ALLOW) {
val &= ~LCPLL_POWER_DOWN_ALLOW;
I915_WRITE(LCPLL_CTL, val);
@ -6060,6 +6064,8 @@ void hsw_restore_lcpll(struct drm_i915_private *dev_priv)
LCPLL_CD_SOURCE_FCLK_DONE) == 0, 1))
DRM_ERROR("Switching back to LCPLL failed\n");
}
dev_priv->uncore.funcs.force_wake_put(dev_priv);
}
static void haswell_modeset_global_resources(struct drm_device *dev)