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

[ Upstream commit 5df0582b ]

Looks like it was introduced in:

commit 650ad970
Author: Imre Deak <imre.deak@intel.com>
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
85250ddf "drm/i915/chv: Remove Wait for a previous gfx force-off"
and 8d4eee9c "drm/i915: vlv: increase timeout when forcing on the
GFX clock") and doesn't seem to be required, so let's just drop it.

References: https://bugs.freedesktop.org/show_bug.cgi?id=89611Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Deepak S <deepak.s@linux.intel.com>
Cc: stable@vger.kernel.org # c9c52e24: drm/i915/chv: Remove Wait ...
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -1244,11 +1244,13 @@ int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool force_on)
 	int err;
 
 	val = I915_READ(VLV_GTLC_SURVIVABILITY_REG);
-	WARN_ON(!!(val & VLV_GFX_CLK_FORCE_ON_BIT) == force_on);
 
 #define COND (I915_READ(VLV_GTLC_SURVIVABILITY_REG) & VLV_GFX_CLK_STATUS_BIT)
 	/* Wait for a previous force-off to settle */
-	if (force_on) {
+	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",