[Intel-gfx] [PATCH v4 1/2] drm/i915/dp: Enable DP audio stall fix for gen9 platforms

[Dhinakaran Pandiyan]

Enabling DP audio stall fix is necessary to play audio over DP HBR2. So,
let's set this bit right before enabling the audio codec. Playing audio
without setting this bit results in pipe FIFO underruns.

This workaround is applicable only for audio sample rates up to 96kHz. For
frequencies above 96kHz, this is insufficient and cdclk should be increased
to at least 432 MHz, just like BDW. Since, the audio driver does not
support sample rates > 48 kHz, we are safe with this fix for now.

v2: Inlined the code change within hsw_audio_codec_enable() (Jani)
    Fixed the port clock typo
    Added TODO comment
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h    |  5 +++++
 drivers/gpu/drm/i915/intel_audio.c | 30 +++++++++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 00efaa1..76dac48 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6236,6 +6236,11 @@ enum {
 #define SLICE_ECO_CHICKEN0			_MMIO(0x7308)
 #define   PIXEL_MASK_CAMMING_DISABLE		(1 << 14)
 
+#define _CHICKEN_TRANS_A	0x420C0
+#define _CHICKEN_TRANS_B	0x420C4
+#define CHICKEN_TRANS(tran) _MMIO_TRANS(tran, _CHICKEN_TRANS_A, _CHICKEN_TRANS_B)
+#define SPARE_13	(1<<13)
+
 /* WaCatErrorRejectionIssue */
 #define GEN7_SQ_CHICKEN_MBCUNIT_CONFIG		_MMIO(0x9030)
 #define  GEN7_SQ_CHICKEN_MBCUNIT_SQINTMOB	(1<<11)
diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
index 7093cfb..894f11e 100644
--- a/drivers/gpu/drm/i915/intel_audio.c
+++ b/drivers/gpu/drm/i915/intel_audio.c
@@ -283,6 +283,8 @@ static void hsw_audio_codec_disable(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct intel_crtc *intel_crtc = to_intel_crtc(encoder->base.crtc);
+	struct intel_crtc_state *crtc_config =  intel_crtc->config;
+	enum transcoder cpu_transcoder = crtc_config->cpu_transcoder;
 	enum pipe pipe = intel_crtc->pipe;
 	uint32_t tmp;
 
@@ -290,13 +292,21 @@ static void hsw_audio_codec_disable(struct intel_encoder *encoder)
 
 	mutex_lock(&dev_priv->av_mutex);
 
+	/*Disable DP audio stall fix for HBR2*/
+	if (IS_GEN9(dev_priv) && intel_crtc_has_dp_encoder(crtc_config) &&
+	    crtc_config->port_clock >= 540000) {
+		tmp = I915_READ(CHICKEN_TRANS(cpu_transcoder));
+		tmp &= ~SPARE_13;
+		I915_WRITE(CHICKEN_TRANS(cpu_transcoder), tmp);
+	}
+
 	/* Disable timestamps */
 	tmp = I915_READ(HSW_AUD_CFG(pipe));
 	tmp &= ~AUD_CONFIG_N_VALUE_INDEX;
 	tmp |= AUD_CONFIG_N_PROG_ENABLE;
 	tmp &= ~AUD_CONFIG_UPPER_N_MASK;
 	tmp &= ~AUD_CONFIG_LOWER_N_MASK;
-	if (intel_crtc_has_dp_encoder(intel_crtc->config))
+	if (intel_crtc_has_dp_encoder(crtc_config))
 		tmp |= AUD_CONFIG_N_VALUE_INDEX;
 	I915_WRITE(HSW_AUD_CFG(pipe), tmp);
 
@@ -315,6 +325,8 @@ static void hsw_audio_codec_enable(struct drm_connector *connector,
 {
 	struct drm_i915_private *dev_priv = to_i915(connector->dev);
 	struct intel_crtc *intel_crtc = to_intel_crtc(intel_encoder->base.crtc);
+	struct intel_crtc_state *crtc_config =  intel_crtc->config;
+	enum transcoder cpu_transcoder = crtc_config->cpu_transcoder;
 	enum pipe pipe = intel_crtc->pipe;
 	enum port port = intel_encoder->port;
 	const uint8_t *eld = connector->eld;
@@ -326,6 +338,22 @@ static void hsw_audio_codec_enable(struct drm_connector *connector,
 
 	mutex_lock(&dev_priv->av_mutex);
 
+	/* Enable DP audio stall fix for HBR2
+	 *
+	 * TODO: This workaround is applicable only for audio sample rates up
+	 * to 96kHz. For frequencies above 96kHz, this is insufficient and
+	 * cdclk should be increased to at least 432 MHz, just like BDW. Since,
+	 * the audio driver does not support sample rates > 48 kHz, we are safe
+	 * with this fix for now.
+	 */
+
+	if (IS_GEN9(dev_priv) && intel_crtc_has_dp_encoder(crtc_config) &&
+	    crtc_config->port_clock >= 540000) {
+		tmp = I915_READ(CHICKEN_TRANS(cpu_transcoder));
+		tmp |= SPARE_13;
+		I915_WRITE(CHICKEN_TRANS(cpu_transcoder), tmp);
+	}
+
 	/* Enable audio presence detect, invalidate ELD */
 	tmp = I915_READ(HSW_AUD_PIN_ELD_CP_VLD);
 	tmp |= AUDIO_OUTPUT_ENABLE(pipe);
-- 
2.7.4