drm/i915: save AUD_FREQ_CNTRL state at audio domain suspend

When audio power domain is suspended, the display driver must
save state of AUD_FREQ_CNTRL on Tiger Lake and Ice Lake
systems. The initial value of the register is set by BIOS and
is read by driver during the audio component init sequence.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190920083918.27057-1-kai.vehmanen@linux.intel.com

drivers/gpu/drm/i915/display/intel_audio.c

@@ -852,10 +852,17 @@ static unsigned long i915_audio_component_get_power(struct device *kdev)
 
 	ret = intel_display_power_get(dev_priv, POWER_DOMAIN_AUDIO);
 
-	/* Force CDCLK to 2*BCLK as long as we need audio to be powered. */
-	if (dev_priv->audio_power_refcount++ == 0)
+	if (dev_priv->audio_power_refcount++ == 0) {
+		if (IS_TIGERLAKE(dev_priv) || IS_ICELAKE(dev_priv)) {
+			I915_WRITE(AUD_FREQ_CNTRL, dev_priv->audio_freq_cntrl);
+			DRM_DEBUG_KMS("restored AUD_FREQ_CNTRL to 0x%x\n",
+				      dev_priv->audio_freq_cntrl);
+		}
+
+		/* Force CDCLK to 2*BCLK as long as we need audio powered. */
 		if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
 			glk_force_audio_cdclk(dev_priv, true);
+	}
 
 	return ret;
 }
@@ -1116,6 +1123,12 @@ static void i915_audio_component_init(struct drm_i915_private *dev_priv)
 		return;
 	}
 
+	if (IS_TIGERLAKE(dev_priv) || IS_ICELAKE(dev_priv)) {
+		dev_priv->audio_freq_cntrl = I915_READ(AUD_FREQ_CNTRL);
+		DRM_DEBUG_KMS("init value of AUD_FREQ_CNTRL of 0x%x\n",
+			      dev_priv->audio_freq_cntrl);
+	}
+
 	dev_priv->audio_component_registered = true;
 }
 

drivers/gpu/drm/i915/i915_drv.h

@@ -1541,6 +1541,7 @@ struct drm_i915_private {
 	 */
 	struct mutex av_mutex;
 	int audio_power_refcount;
+	u32 audio_freq_cntrl;
 
 	struct {
 		struct mutex mutex;

drivers/gpu/drm/i915/i915_reg.h

@@ -9127,6 +9127,8 @@ enum {
 #define HSW_AUD_CHICKENBIT			_MMIO(0x65f10)
 #define   SKL_AUD_CODEC_WAKE_SIGNAL		(1 << 15)
 
+#define AUD_FREQ_CNTRL			_MMIO(0x65900)
+
 /*
  * HSW - ICL power wells
  *