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

From: Jani Nikula <jani.nikula@intel.com>
To: intel-gfx@lists.freedesktop.org
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Subject: Re: [PATCH v4 1/2] drm/i915/dp: Enable DP audio stall fix for gen9 platforms
Date: Wed, 26 Oct 2016 11:57:31 +0300	[thread overview]
Message-ID: <871sz3mqro.fsf@intel.com> (raw)
In-Reply-To: <1477449456-22146-1-git-send-email-dhinakaran.pandiyan@intel.com>

On Wed, 26 Oct 2016, Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> 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@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*/

Nitpick, spaces after /* and before */.

> +	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);
> +	}

Hmm. Why don't we just do this unconditionally?

> +
>  	/* 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.
> +	 */

Is this TODO required if you already have that check in patch 2/2?

> +
> +	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);

-- 
Jani Nikula, Intel Open Source Technology Center
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