[PATCH] drm/i915: Implement Audio WA_14020863754

[Shankar, Uma]

> -----Original Message-----
> From: Jani Nikula <jani.nikula at linux.intel.com>
> Sent: Wednesday, April 10, 2024 3:47 PM
> To: Shankar, Uma <uma.shankar at intel.com>; intel-gfx at lists.freedesktop.org;
> intel-xe at lists.freedesktop.org
> Cc: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>; Shankar, Uma
> <uma.shankar at intel.com>
> Subject: Re: [PATCH] drm/i915: Implement Audio WA_14020863754
> 
> On Wed, 10 Apr 2024, Uma Shankar <uma.shankar at 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.

Yes Jani, realized it after sending. Will update and re-float.
Thanks for spotting it.

Regards,
Uma Shankar

> BR,
> Jani.
> 
> >
> > Signed-off-by: Uma Shankar <uma.shankar at 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