Re: [PATCH v3 1/2] drm/i915/dp: Enable DP audio stall fix for gen9 platforms

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Mixing up git rebase and reset was not a good idea, will send the
corrected patch. Please ignore this.

On Tue, 2016-10-25 at 16:42 -0700, Dhinakaran Pandiyan wrote:
> 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@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/i915_reg.h    |  5 +++
>  drivers/gpu/drm/i915/intel_audio.c | 62 +++++++++++++++++++++++++++++++++++---
>  2 files changed, 62 insertions(+), 5 deletions(-)
> 
> 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..413dd50 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);
> @@ -642,25 +670,49 @@ static int i915_audio_component_get_cdclk_freq(struct device *kdev)
>  	return dev_priv->cdclk_freq;
>  }
>  
> +/*
> + * get the intel_encoder according to the parameter port and pipe
> + * intel_encoder is saved by the index of pipe
> + * MST & (pipe >= 0): return the av_enc_map[pipe],
> + *   when port is matched
> + * MST & (pipe < 0): this is invalid
> + * Non-MST & (pipe >= 0): only pipe = 0 (the first device entry)
> + *   will get the right intel_encoder with port matched
> + * Non-MST & (pipe < 0): get the right intel_encoder with port matched
> + */
>  static struct intel_encoder *get_saved_enc(struct drm_i915_private *dev_priv,
>  					       int port, int pipe)
>  {
> +	struct intel_encoder *encoder;
>  
>  	if (WARN_ON(pipe >= I915_MAX_PIPES))
>  		return NULL;
>  
>  	/* MST */
> -	if (pipe >= 0)
> -		return dev_priv->av_enc_map[pipe];
> +	if (pipe >= 0) {
> +		encoder = dev_priv->av_enc_map[pipe];
> +		/*
> +		 * when bootup, audio driver may not know it is
> +		 * MST or not. So it will poll all the port & pipe
> +		 * combinations
> +		 */
> +		if (encoder != NULL && encoder->port == port &&
> +		    encoder->type == INTEL_OUTPUT_DP_MST)
> +			return encoder;
> +	}
>  
>  	/* Non-MST */
> -	for_each_pipe(dev_priv, pipe) {
> -		struct intel_encoder *encoder;
> +	if (pipe > 0)
> +		return NULL;
>  
> +	for_each_pipe(dev_priv, pipe) {
>  		encoder = dev_priv->av_enc_map[pipe];
>  		if (encoder == NULL)
>  			continue;
>  
> +		if (encoder->type == INTEL_OUTPUT_DP_MST)
> +			continue;
> +
>  		if (port == encoder->port)
>  			return encoder;
>  	}

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