[v3] drm/i915: Implement Audio WA_14020863754

[Shankar, Uma]

> -----Original Message-----
> From: Jani Nikula <jani.nikula at linux.intel.com>
> Sent: Tuesday, May 7, 2024 4:12 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>; Roper,
> Matthew D <matthew.d.roper at intel.com>; Shankar, Uma
> <uma.shankar at intel.com>
> Subject: Re: [v3] drm/i915: Implement Audio WA_14020863754
> 
> On Mon, 06 May 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)
> >
> > v2: Update the platform checks (Jani Nikula)
> >
> > v3: Limited the WA to LNL and BMG, added a helper (Matt Roper)
> >
> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_audio.c     | 18 ++++++++++++++++++
> >  .../gpu/drm/i915/display/intel_audio_regs.h    |  3 +++
> >  2 files changed, 21 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_audio.c
> > b/drivers/gpu/drm/i915/display/intel_audio.c
> > index ed81e1466c4b..cb055c16dd98 100644
> > --- a/drivers/gpu/drm/i915/display/intel_audio.c
> > +++ b/drivers/gpu/drm/i915/display/intel_audio.c
> > @@ -183,6 +183,18 @@ static const struct hdmi_aud_ncts
> hdmi_aud_ncts_36bpp[] = {
> >  	{ 192000, TMDS_445_5M, 20480, 371250 },  };
> >
> > +/*
> > + * WA_14020863754: Implement Audio Workaround
> > + * Corner case with Min Hblank Fix can cause audio hang  */ static
> > +bool needs_wa_14020863754(struct drm_i915_private *i915) {
> > +	if (DISPLAY_VER(i915) == 20 || IS_BATTLEMAGE(i915))
> 
> Why do we need to check for both display version and the platform?
> Especially weird that it's || and not &&.

Hi Jani,
WA is applicable for display version 20 and any derivative, but it was also
needed on BMG (which is based out of MTL i.e ver14).
Hence added this condition along with a ||.

> > +		return true;
> > +
> > +	return false;
> 
> The whole function is just "return ver == 20 || is_bmg", there's no need to have
> the if and two different return locations.

Yeah right, will drop the redundant if.

Regards,
Uma Shankar

> 
> BR,
> Jani.
> 
> 
> > +}
> > +
> >  /* get AUD_CONFIG_PIXEL_CLOCK_HDMI_* value for mode */  static u32
> > audio_config_hdmi_pixel_clock(const struct intel_crtc_state
> > *crtc_state)  { @@ -415,6 +427,9 @@ 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);
> >
> > +	if (needs_wa_14020863754(i915))
> > +		intel_de_rmw(i915, AUD_CHICKENBIT_REG3,
> CHICKEN3_SPARE18, 0);
> > +
> >  	mutex_unlock(&i915->display.audio.mutex);
> >  }
> >
> > @@ -540,6 +555,9 @@ 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);
> >
> > +	if (needs_wa_14020863754(i915))
> > +		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 88ea2740365d..7de82cd3380e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_audio_regs.h
> > +++ b/drivers/gpu/drm/i915/display/intel_audio_regs.h
> > @@ -164,4 +164,7 @@
> >
> _VLV_AUD_PORT_EN_D_DBG)
> >  #define VLV_AMP_MUTE		        (1 << 1)
> >
> > +#define AUD_CHICKENBIT_REG3		_MMIO(0x65F1C)
> > +#define  CHICKEN3_SPARE18		REG_BIT(18)
> > +
> >  #endif /* __INTEL_AUDIO_REGS_H__ */
> 
> --
> Jani Nikula, Intel