drm/i915: Warn if GPLL isn't used on vlv/chv

Our freq<->opcode conversions assume that GPLL is always used.
Apparently that should be the case always, but let's scream if we
ever encounter something different.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak S<deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -5333,6 +5333,9 @@ static void cherryview_enable_rps(struct drm_device *dev)
 
 	val = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
 
+	/* RPS code assumes GPLL is used */
+	WARN_ONCE((val & GPLLENABLE) == 0, "GPLL not enabled\n");
+
 	DRM_DEBUG_DRIVER("GPLL enabled? %s\n", val & GPLLENABLE ? "yes" : "no");
 	DRM_DEBUG_DRIVER("GPU status: 0x%08x\n", val);
 
@@ -5413,6 +5416,9 @@ static void valleyview_enable_rps(struct drm_device *dev)
 
 	val = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
 
+	/* RPS code assumes GPLL is used */
+	WARN_ONCE((val & GPLLENABLE) == 0, "GPLL not enabled\n");
+
 	DRM_DEBUG_DRIVER("GPLL enabled? %s\n", val & GPLLENABLE ? "yes" : "no");
 	DRM_DEBUG_DRIVER("GPU status: 0x%08x\n", val);