drm/i915/vlv: remove wait for previous GFX clk disable request

Looks like it was introduced in:

commit 650ad97
Author: Imre Deak <[email protected]>
Date:   Fri Apr 18 16:35:02 2014 +0300

    drm/i915: vlv: factor out vlv_force_gfx_clock and check for pending force-of

but I'm not sure why.  It has caused problems for us in the past (see
85250dd "drm/i915/chv: Remove Wait for a previous gfx force-off"
and 8d4eee9 "drm/i915: vlv: increase timeout when forcing on the
GFX clock") and doesn't seem to be required, so let's just drop it.

[airlied: I messed up a merge - readd this]
References: https://bugs.freedesktop.org/show_bug.cgi?id=89611
Signed-off-by: Jesse Barnes <[email protected]>
Tested-by: Darren Hart <[email protected]>
Reviewed-by: Deepak S <[email protected]>
Cc: [email protected] # c9c52e2: drm/i915/chv: Remove Wait ...
Cc: [email protected]
Signed-off-by: Jani Nikula <[email protected]>

drivers/gpu/drm/i915/i915_drv.c

@@ -1240,21 +1240,7 @@ int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool force_on)
 	u32 val;
 	int err;
 
-	val = I915_READ(VLV_GTLC_SURVIVABILITY_REG);
-
 #define COND (I915_READ(VLV_GTLC_SURVIVABILITY_REG) & VLV_GFX_CLK_STATUS_BIT)
-	/* Wait for a previous force-off to settle */
-	if (force_on && !IS_CHERRYVIEW(dev_priv->dev)) {
-		/* WARN_ON only for the Valleyview */
-		WARN_ON(!!(val & VLV_GFX_CLK_FORCE_ON_BIT) == force_on);
-
-		err = wait_for(!COND, 20);
-		if (err) {
-			DRM_ERROR("timeout waiting for GFX clock force-off (%08x)\n",
-				  I915_READ(VLV_GTLC_SURVIVABILITY_REG));
-			return err;
-		}
-	}
 
 	val = I915_READ(VLV_GTLC_SURVIVABILITY_REG);
 	val &= ~VLV_GFX_CLK_FORCE_ON_BIT;