drm/i915/hsw: Avoid early timeout during LCPLL disable/restore

Since wait_for_atomic doesn't re-check the wait-for condition after
expiry of the timeout it can fail when called from non-atomic context
even if the condition is set correctly before the expiry. Fix this by
using the non-atomic wait_for instead.

Fixes: 0351b93 ("drm/i915: Do not lie about atomic timeout granularity")
CC: Chris Wilson <chris@chris-wilson.co.uk>
CC: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
CC: drm-intel-fixes@lists.freedesktop.org
Link: http://patchwork.freedesktop.org/patch/msgid/1467110253-16046-4-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -9534,8 +9534,8 @@ static void hsw_disable_lcpll(struct drm_i915_private *dev_priv,
 		val |= LCPLL_CD_SOURCE_FCLK;
 		I915_WRITE(LCPLL_CTL, val);
 
-		if (wait_for_atomic_us(I915_READ(LCPLL_CTL) &
-				       LCPLL_CD_SOURCE_FCLK_DONE, 1))
+		if (wait_for_us(I915_READ(LCPLL_CTL) &
+				LCPLL_CD_SOURCE_FCLK_DONE, 1))
 			DRM_ERROR("Switching to FCLK failed\n");
 
 		val = I915_READ(LCPLL_CTL);
@@ -9608,8 +9608,8 @@ static void hsw_restore_lcpll(struct drm_i915_private *dev_priv)
 		val &= ~LCPLL_CD_SOURCE_FCLK;
 		I915_WRITE(LCPLL_CTL, val);
 
-		if (wait_for_atomic_us((I915_READ(LCPLL_CTL) &
-					LCPLL_CD_SOURCE_FCLK_DONE) == 0, 1))
+		if (wait_for_us((I915_READ(LCPLL_CTL) &
+				 LCPLL_CD_SOURCE_FCLK_DONE) == 0, 1))
 			DRM_ERROR("Switching back to LCPLL failed\n");
 	}