[v2] drm/i915: Implement Audio WA_14020863754

[Matt Roper]

On Thu, Apr 11, 2024 at 03:36:37PM -0700, Matt Roper wrote:
> On Wed, Apr 10, 2024 at 07:20:46PM +0530, Uma Shankar 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)
> > 
> > v2: Update the platform checks (Jani Nikula)
> > 
> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_audio.c      | 14 ++++++++++++++
> >  drivers/gpu/drm/i915/display/intel_audio_regs.h |  3 +++
> >  2 files changed, 17 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_audio.c b/drivers/gpu/drm/i915/display/intel_audio.c
> > index 07e0c73204f3..61df5115c970 100644
> > --- a/drivers/gpu/drm/i915/display/intel_audio.c
> > +++ b/drivers/gpu/drm/i915/display/intel_audio.c
> > @@ -512,6 +512,13 @@ 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
> > +	 */
> > +	if (DISPLAY_VER(i915) >= 20)
> 
> The workaround is currently listed as applying to both Xe2_LPD (20.00)
> and Xe2_HPD (14.01).  So we should match on those precise IP versions
> for now.  Future platforms and/or refreshes may or may not need this
> workaround and we don't want to just assume the workaround will carry
> forward forever, so the condition may get updated further as new
> platforms/IP versions are added to the driver.

Also, since this is a workaround that requires logic in multiple spots
and already applies to multiple IP versions, it may be a good idea to
separate out the condition into a helper function so that if/when new
versions get added to the list in the future we can update a single
place rather than tracking down multiple 'if' statements.


Matt

> 
> 
> Matt
> 
> > +		intel_de_rmw(i915, AUD_CHICKENBIT_REG3, CHICKEN3_SPARE18, 0);
> > +
> >  	mutex_unlock(&i915->display.audio.mutex);
> >  }
> >  
> > @@ -637,6 +644,13 @@ 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
> > +	 */
> > +	if (DISPLAY_VER(i915) >= 20)
> > +		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__ */
> > -- 
> > 2.42.0
> > 
> 
> -- 
> Matt Roper
> Graphics Software Engineer
> Linux GPU Platform Enablement
> Intel Corporation

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation