[alsa-devel] [Intel-gfx] [PATCH v4 4/4] drm/i915: set proper N/CTS in modeset

[Yang, Libin]

Hi Jani,

Thanks for careful reviewing for all the patches, please
see my comments.

> -----Original Message-----
> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
> Sent: Monday, August 10, 2015 8:10 PM
> To: Yang, Libin; alsa-devel at alsa-project.org; tiwai at suse.de; intel-
> gfx at lists.freedesktop.org; daniel.vetter at ffwll.ch
> Subject: Re: [Intel-gfx] [PATCH v4 4/4] drm/i915: set proper N/CTS in
> modeset
> 
> On Mon, 10 Aug 2015, libin.yang at intel.com wrote:
> > From: Libin Yang <libin.yang at intel.com>
> >
> > When modeset occurs and the TMDS frequency is set to some
> > speical value, the N/CTS need to be set manually if audio
> > is playing.
> 
> When modeset occurs, we disable everything, and then re-enable
> everything, and notify the audio driver every step of the way. IIUC
> there should be no audio playing across the modeset, and when the
> modeset is complete and we've set the valid ELD, the audio driver
> should
> call the callback from the earlier patches to set the correct audio
> rate.
> 
> Why is this patch needed? Please enlighten me.

Please image this scenario: when audio is playing, the gfx driver
does the modeset. In this situation, after modeset, audio driver
will do nothing and continue playing. And audio driver will not call
set_ncts. 

> 
> Also some comments in-line, provided you've convinced me first. ;)
> 
> > Signed-off-by: Libin Yang <libin.yang at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h    |  6 ++++++
> >  drivers/gpu/drm/i915/intel_audio.c | 42
> ++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 48 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> b/drivers/gpu/drm/i915/i915_reg.h
> > index da2d128..85f3beb 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -7030,6 +7030,12 @@ enum skl_disp_power_wells {
> >  					_HSW_AUD_DIG_CNVT_2)
> >  #define DIP_PORT_SEL_MASK		0x3
> >
> > +#define _HSW_AUD_STR_DESC_1		0x65084
> > +#define _HSW_AUD_STR_DESC_2		0x65184
> > +#define AUD_STR_DESC(pipe)	_PIPE(pipe, \
> > +					 _HSW_AUD_STR_DESC_1,
> 	\
> > +					 _HSW_AUD_STR_DESC_2)
> > +
> >  #define _HSW_AUD_EDID_DATA_A		0x65050
> >  #define _HSW_AUD_EDID_DATA_B		0x65150
> >  #define HSW_AUD_EDID_DATA(pipe) _PIPE(pipe, \
> > diff --git a/drivers/gpu/drm/i915/intel_audio.c
> b/drivers/gpu/drm/i915/intel_audio.c
> > index eddf37f..082f96d 100644
> > --- a/drivers/gpu/drm/i915/intel_audio.c
> > +++ b/drivers/gpu/drm/i915/intel_audio.c
> > @@ -235,6 +235,9 @@ static void hsw_audio_codec_enable(struct
> drm_connector *connector,
> >  	const uint8_t *eld = connector->eld;
> >  	uint32_t tmp;
> >  	int len, i;
> > +	int cvt_idx;
> > +	int n_low, n_up, n;
> > +	int base_rate, mul, div, rate;
> >
> >  	DRM_DEBUG_KMS("Enable audio codec on pipe %c, %u bytes
> ELD\n",
> >  		      pipe_name(pipe), drm_eld_size(eld));
> > @@ -267,6 +270,21 @@ static void hsw_audio_codec_enable(struct
> drm_connector *connector,
> >  	tmp |= AUDIO_ELD_VALID(pipe);
> >  	I915_WRITE(HSW_AUD_PIN_ELD_CP_VLD, tmp);
> >
> > +	if ((mode->clock == 297000) ||
> > +		(mode->clock == DIV_ROUND_UP(297000 * 1000,
> 1001))) {
> > +		tmp = I915_READ(HSW_AUD_PIPE_CONN_SEL_CTRL);
> > +		cvt_idx = (tmp >> pipe*8) & 0xff;
> > +		tmp = I915_READ(AUD_STR_DESC(cvt_idx));
> > +		base_rate = tmp & (1 << 14);
> > +		if (base_rate == 0)
> > +			rate = 48000;
> > +		else
> > +			rate = 44100;
> > +		mul = (tmp & (0x7 << 11)) + 1;
> > +		div = (tmp & (0x7 << 8)) + 1;
> > +		rate = rate * mul / div;
> > +	}
> 
> This should be abstracted to a separate function.

Yes. I will do it.

> 
> > +
> >  	/* Enable timestamps */
> >  	tmp = I915_READ(HSW_AUD_CFG(pipe));
> >  	tmp &= ~AUD_CONFIG_N_VALUE_INDEX;
> > @@ -276,6 +294,30 @@ static void hsw_audio_codec_enable(struct
> drm_connector *connector,
> >  		tmp |= AUD_CONFIG_N_VALUE_INDEX;
> >  	else
> >  		tmp |= audio_config_hdmi_pixel_clock(mode);
> > +
> > +	if ((mode->clock != 297000) &&
> > +		(mode->clock != DIV_ROUND_UP(297000 * 1000,
> 1001))) {
> > +		tmp &= ~AUD_CONFIG_N_PROG_ENABLE;
> > +	} else {
> > +		for (i = 0; i < ARRAY_SIZE(aud_ncts); i++) {
> > +			if ((rate == aud_ncts[i].sample_rate) &&
> > +				(mode->clock == aud_ncts[i].clock)) {
> > +				n = aud_ncts[i].n;
> > +				break;
> > +			}
> > +		}
> > +		if (n != 0) {
> > +			tmp |= AUD_CONFIG_N_PROG_ENABLE;
> > +			n_low = n & 0xfff;
> > +			n_up = (n >> 12) & 0xff;
> > +			tmp |= AUD_CONFIG_N_PROG_ENABLE;
> > +			tmp &= ~AUD_CONFIG_UPPER_N_MASK;
> > +			tmp |= (n_up <<
> AUD_CONFIG_UPPER_N_SHIFT);
> > +			tmp &= ~AUD_CONFIG_LOWER_N_MASK;
> > +			tmp |= (n_low <<
> AUD_CONFIG_LOWER_N_SHIFT);
> > +		}
> > +	}
> 
> Please de-duplicate the copy-paste from patch 2. At the very least you
> should use a helper for finding the parameters from the table.

OK. I see.

Regards,
Libin

> 
> > +
> >  	I915_WRITE(HSW_AUD_CFG(pipe), tmp);
> >  }
> >
> > --
> > 1.9.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> --
> Jani Nikula, Intel Open Source Technology Center