Re: [PATCH] drm/i915: Implement Audio WA_14020863754

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 10 Apr 2024, Uma Shankar <uma.shankar@intel.com> wrote:
> WA_14020863754: Corner case with Min Hblank Fix can cause
> audio hang
>
> Issue: Previously a fix was made to avoid issues with extremely
> small hblanks, called the "Min Hblank Fix". However, this can
> potentially cause an audio hang.
>
> Workaround :
> During "Audio Programming Sequence" Audio Enabling -
> When DP mode is enabled Set mmio offset 0x65F1C bit 18 = 1b,
> before step #1 "Enable audio Presence Detect"
>
> During "Audio Programming Sequence" Audio Disabling -
> When DP mode is enabled Clear mmio offset 0x65F1C bit 18 = 0b,
> after step #6 "Disable Audio PD (Presence Detect)"
> If not clearing PD bit, must also not clear 0x65F1C bit 18 (leave = 1b)

hsw_audio_codec_disable/enable get called on hsw and display ver >= 8,
but a lot of those platforms have the bit reserved MBZ. I didn't go
through all the platforms in bspec, but enough to notice this needs some
platform check.

BR,
Jani.

>
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_audio.c      | 12 ++++++++++++
>  drivers/gpu/drm/i915/display/intel_audio_regs.h |  3 +++
>  2 files changed, 15 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_audio.c b/drivers/gpu/drm/i915/display/intel_audio.c
> index 07e0c73204f3..a8e3e515aaa0 100644
> --- a/drivers/gpu/drm/i915/display/intel_audio.c
> +++ b/drivers/gpu/drm/i915/display/intel_audio.c
> @@ -512,6 +512,12 @@ static void hsw_audio_codec_disable(struct intel_encoder *encoder,
>  	intel_de_rmw(i915, HSW_AUD_PIN_ELD_CP_VLD,
>  		     AUDIO_OUTPUT_ENABLE(cpu_transcoder), 0);
>  
> +	/*
> +	 * WA_14020863754: Implement Audio Workaround
> +	 * Corner case with Min Hblank Fix can cause audio hang
> +	 */
> +	intel_de_rmw(i915, AUD_CHICKENBIT_REG3, CHICKEN3_SPARE18, 0);
> +
>  	mutex_unlock(&i915->display.audio.mutex);
>  }
>  
> @@ -637,6 +643,12 @@ static void hsw_audio_codec_enable(struct intel_encoder *encoder,
>  	if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP))
>  		enable_audio_dsc_wa(encoder, crtc_state);
>  
> +	/*
> +	 * WA_14020863754: Implement Audio Workaround
> +	 * Corner case with Min Hblank Fix can cause audio hang
> +	 */
> +	intel_de_rmw(i915, AUD_CHICKENBIT_REG3, 0, CHICKEN3_SPARE18);
> +
>  	/* Enable audio presence detect */
>  	intel_de_rmw(i915, HSW_AUD_PIN_ELD_CP_VLD,
>  		     0, AUDIO_OUTPUT_ENABLE(cpu_transcoder));
> diff --git a/drivers/gpu/drm/i915/display/intel_audio_regs.h b/drivers/gpu/drm/i915/display/intel_audio_regs.h
> index 616e7b1275c4..6f8d33299ecd 100644
> --- a/drivers/gpu/drm/i915/display/intel_audio_regs.h
> +++ b/drivers/gpu/drm/i915/display/intel_audio_regs.h
> @@ -148,4 +148,7 @@
>  #define HBLANK_START_COUNT_96	4
>  #define HBLANK_START_COUNT_128	5
>  
> +#define AUD_CHICKENBIT_REG3		_MMIO(0x65F1C)
> +#define  CHICKEN3_SPARE18		REG_BIT(18)
> +
>  #endif /* __INTEL_AUDIO_REGS_H__ */

-- 
Jani Nikula, Intel