drm/i915: Warn about odd rps values on CHV

CHV wants even rps opcodes so print a warning of the
min/max/rpe/rp1 values are odd, and warn if an odd value
slips through to valleyview_set_rps() and truncate it to
an even value.

Also add a comment to chv_freq_opcode() to make sure no one
changes the code without considering this requirement.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak S <deepak.s@linux.intel.com>
[danvet: Help git along in applying the patch, somehow it silently
ended up in the vlv init_gt_powersave function.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -3477,6 +3477,10 @@ void valleyview_set_rps(struct drm_device *dev, u8 val)
 			 dev_priv->rps.cur_freq,
 			 vlv_gpu_freq(dev_priv, val), val);
 
+	if (WARN_ONCE(IS_CHERRYVIEW(dev) && (val & 1),
+		      "Odd GPU freq value\n"))
+		val &= ~1;
+
 	if (val != dev_priv->rps.cur_freq)
 		vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
 
@@ -4364,6 +4368,12 @@ static void cherryview_init_gt_powersave(struct drm_device *dev)
 			 vlv_gpu_freq(dev_priv, dev_priv->rps.min_freq),
 			 dev_priv->rps.min_freq);
 
+	WARN_ONCE((dev_priv->rps.max_freq |
+		   dev_priv->rps.efficient_freq |
+		   dev_priv->rps.rp1_freq |
+		   dev_priv->rps.min_freq) & 1,
+		  "Odd GPU freq values\n");
+
 	/* Preserve min/max settings in case of re-init */
 	if (dev_priv->rps.max_freq_softlimit == 0)
 		dev_priv->rps.max_freq_softlimit = dev_priv->rps.max_freq;
@@ -7566,6 +7576,7 @@ static int chv_freq_opcode(struct drm_i915_private *dev_priv, int val)
 		return -1;
 	}
 
+	/* CHV needs even values */
 	opcode = (DIV_ROUND_CLOSEST((val * 2 * mul), dev_priv->rps.cz_freq) * 2);
 
 	return opcode;