drm/i915/display: program audio CDCLK-TS for keepalives

XE_LPD display adds support for display audio codec keepalive feature.
This feature works also when display codec is in D3 state and the audio
link is off (BCLK off). To enable this functionality, display driver
must update the AUD_TS_CDCLK_M/N registers whenever CDCLK is changed.
Actual timestamps are generated only when the audio codec driver
specifically enables the KeepAlive (KAE) feature.

This patch adds new hooks to intel_set_cdclk() in order to inform
display audio driver when CDCLK change is started and when it is
complete.

Bspec: 53679
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211021105915.4128635-1-kai.vehmanen@linux.intel.com

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

@@ -947,6 +947,40 @@ void intel_init_audio_hooks(struct drm_i915_private *dev_priv)
 	}
 }
 
+struct aud_ts_cdclk_m_n {
+	u8 m;
+	u16 n;
+};
+
+void intel_audio_cdclk_change_pre(struct drm_i915_private *i915)
+{
+	if (DISPLAY_VER(i915) >= 13)
+		intel_de_rmw(i915, AUD_TS_CDCLK_M, AUD_TS_CDCLK_M_EN, 0);
+}
+
+static void get_aud_ts_cdclk_m_n(int refclk, int cdclk, struct aud_ts_cdclk_m_n *aud_ts)
+{
+	if (refclk == 24000)
+		aud_ts->m = 12;
+	else
+		aud_ts->m = 15;
+
+	aud_ts->n = cdclk * aud_ts->m / 24000;
+}
+
+void intel_audio_cdclk_change_post(struct drm_i915_private *i915)
+{
+	struct aud_ts_cdclk_m_n aud_ts;
+
+	if (DISPLAY_VER(i915) >= 13) {
+		get_aud_ts_cdclk_m_n(i915->cdclk.hw.ref, i915->cdclk.hw.cdclk, &aud_ts);
+
+		intel_de_write(i915, AUD_TS_CDCLK_N, aud_ts.n);
+		intel_de_write(i915, AUD_TS_CDCLK_M, aud_ts.m | AUD_TS_CDCLK_M_EN);
+		drm_dbg_kms(&i915->drm, "aud_ts_cdclk set to M=%u, N=%u\n", aud_ts.m, aud_ts.n);
+	}
+}
+
 static int glk_force_audio_cdclk_commit(struct intel_atomic_state *state,
 					struct intel_crtc *crtc,
 					bool enable)
@@ -1330,6 +1364,9 @@ static void i915_audio_component_init(struct drm_i915_private *dev_priv)
 		dev_priv->audio_freq_cntrl = aud_freq;
 	}
 
+	/* init with current cdclk */
+	intel_audio_cdclk_change_post(dev_priv);
+
 	dev_priv->audio_component_registered = true;
 }
 

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

@@ -18,6 +18,8 @@ void intel_audio_codec_enable(struct intel_encoder *encoder,
 void intel_audio_codec_disable(struct intel_encoder *encoder,
 			       const struct intel_crtc_state *old_crtc_state,
 			       const struct drm_connector_state *old_conn_state);
+void intel_audio_cdclk_change_pre(struct drm_i915_private *dev_priv);
+void intel_audio_cdclk_change_post(struct drm_i915_private *dev_priv);
 void intel_audio_init(struct drm_i915_private *dev_priv);
 void intel_audio_deinit(struct drm_i915_private *dev_priv);
 

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

@@ -24,6 +24,7 @@
 #include <linux/time.h>
 
 #include "intel_atomic.h"
+#include "intel_audio.h"
 #include "intel_bw.h"
 #include "intel_cdclk.h"
 #include "intel_de.h"
@@ -1975,6 +1976,8 @@ static void intel_set_cdclk(struct drm_i915_private *dev_priv,
 		intel_psr_pause(intel_dp);
 	}
 
+	intel_audio_cdclk_change_pre(dev_priv);
+
 	/*
 	 * Lock aux/gmbus while we change cdclk in case those
 	 * functions use cdclk. Not all platforms/ports do,
@@ -2003,6 +2006,8 @@ static void intel_set_cdclk(struct drm_i915_private *dev_priv,
 		intel_psr_resume(intel_dp);
 	}
 
+	intel_audio_cdclk_change_post(dev_priv);
+
 	if (drm_WARN(&dev_priv->drm,
 		     intel_cdclk_changed(&dev_priv->cdclk.hw, cdclk_config),
 		     "cdclk state doesn't match!\n")) {

drivers/gpu/drm/i915/i915_reg.h

@@ -9782,6 +9782,10 @@ enum {
 #define AUD_PIN_BUF_CTL		_MMIO(0x48414)
 #define   AUD_PIN_BUF_ENABLE		REG_BIT(31)
 
+#define AUD_TS_CDCLK_M			_MMIO(0x65ea0)
+#define   AUD_TS_CDCLK_M_EN		REG_BIT(31)
+#define AUD_TS_CDCLK_N			_MMIO(0x65ea4)
+
 /* Display Audio Config Reg */
 #define AUD_CONFIG_BE			_MMIO(0x65ef0)
 #define HBLANK_EARLY_ENABLE_ICL(pipe)		(0x1 << (20 - (pipe)))