[Intel-gfx] [PATCH v2] drm/i915/audio: fix hdmi audio noise issue

[Yang, Libin]

> -----Original Message-----
> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
> Sent: Friday, November 11, 2016 4:41 PM
> To: Yang, Libin <libin.yang at intel.com>; intel-gfx at lists.freedesktop.org;
> ville.syrjala at linux.intel.com; Vetter, Daniel <daniel.vetter at intel.com>;
> tiwai at suse.de
> Subject: RE: [PATCH v2] drm/i915/audio: fix hdmi audio noise issue
> 
> On Fri, 11 Nov 2016, "Yang, Libin" <libin.yang at intel.com> wrote:
> > Hi Jani,
> >
> >> -----Original Message-----
> >> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
> >> Sent: Thursday, November 10, 2016 6:37 PM
> >> To: Yang, Libin <libin.yang at intel.com>;
> >> intel-gfx at lists.freedesktop.org; ville.syrjala at linux.intel.com;
> >> Vetter, Daniel <daniel.vetter at intel.com>; tiwai at suse.de
> >> Cc: Yang, Libin <libin.yang at intel.com>
> >> Subject: Re: [PATCH v2] drm/i915/audio: fix hdmi audio noise issue
> >>
> >> On Thu, 10 Nov 2016, libin.yang at intel.com wrote:
> >> > From: Libin Yang <libin.yang at intel.com>
> >> >
> >> > Some monitors will have noise or even no sound after applying the
> >> > patch 6014ac12.
> >> >
> >> > In patch 6014ac12, it will reset the cts value to 0 for HDMI.
> >> > However, we need to disable Enable CTS or M Prog bit. This is the
> >> > initial setting after HW reset.
> >> >
> >> > Fixes: 6014ac122ed0 ("drm/i915/audio: set proper N/M in modeset")
> >> > Signed-off-by: Libin Yang <libin.yang at intel.com>
> >> > ---
> >> >  drivers/gpu/drm/i915/intel_audio.c | 15 ++++++++++++---
> >> >  1 file changed, 12 insertions(+), 3 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/i915/intel_audio.c
> >> > b/drivers/gpu/drm/i915/intel_audio.c
> >> > index 813fd74..a472d35 100644
> >> > --- a/drivers/gpu/drm/i915/intel_audio.c
> >> > +++ b/drivers/gpu/drm/i915/intel_audio.c
> >> > @@ -332,6 +332,13 @@ hsw_hdmi_audio_config_update(struct
> intel_crtc
> >> *intel_crtc, enum port port,
> >> >  	int n;
> >> >  	u32 tmp;
> >> >
> >> > +	/* reset CTS value to 0 */
> >> > +	tmp = I915_READ(HSW_AUD_M_CTS_ENABLE(pipe));
> >> > +	tmp &= ~AUD_CONFIG_M_MASK;
> >> > +	tmp &= ~AUD_M_CTS_M_VALUE_INDEX;
> >> > +	tmp |= AUD_M_CTS_M_PROG_ENABLE;
> >> > +	I915_WRITE(HSW_AUD_M_CTS_ENABLE(pipe), tmp);
> >> > +
> >> >  	tmp = I915_READ(HSW_AUD_CFG(pipe));
> >> >  	tmp &= ~AUD_CONFIG_N_VALUE_INDEX;
> >> >  	tmp &= ~AUD_CONFIG_PIXEL_CLOCK_HDMI_MASK;
> >> > @@ -351,10 +358,12 @@ hsw_hdmi_audio_config_update(struct
> >> > intel_crtc *intel_crtc, enum port port,
> >> >
> >> >  	I915_WRITE(HSW_AUD_CFG(pipe), tmp);
> >> >
> >> > +	/*
> >> > +	 * Let's disable "Enable CTS or M Prog bit"
> >> > +	 * and let HW calculate the value
> >> > +	 */
> >> >  	tmp = I915_READ(HSW_AUD_M_CTS_ENABLE(pipe));
> >> > -	tmp &= ~AUD_CONFIG_M_MASK;
> >> > -	tmp &= ~AUD_M_CTS_M_VALUE_INDEX;
> >> > -	tmp |= AUD_M_CTS_M_PROG_ENABLE;
> >> > +	tmp &= ~AUD_M_CTS_M_PROG_ENABLE;
> >> >  	I915_WRITE(HSW_AUD_M_CTS_ENABLE(pipe), tmp);
> >>
> >> You did not address my review comment on the earlier version:
> >>
> >> Is it necessary to do the HSW_AUD_M_CTS_ENABLE updates in two places?
> >> Why do you both enable and disable AUD_M_CTS_M_PROG_ENABLE bit
> here?
> >
> > Sorry, I missed your comments.
> >
> > The first doing the HSW_AUD_M_CTS_ENABLE is to reset the M value to 0.
> > The second doing the HSW_AUD_M_CTS_ENABLE is to let HW calculate the
> M value.
> >
> > Or we can just try to disable the HSW_AUD_M_CTS_ENABLE bit. What's
> your opinion?
> 
> I would have thought just doing the latter would be sufficient. Please test.

I have done the test on 32KHz, 44.1KHz, 48KHz, 88KHz, it is OK.

Regards,
Libin

> 
> BR,
> Jani.
> 
> >
> > Regards,
> > Libin
> >
> >>
> >> BR,
> >> Jani.
> >>
> >>
> >> >  }
> >>
> >> --
> >> Jani Nikula, Intel Open Source Technology Center
> 
> --
> Jani Nikula, Intel Open Source Technology Center