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

Yang, Libin libin.yang at intel.com
Wed Aug 12 09:28:25 CEST 2015 

Hi Jani,

> -----Original Message-----
> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
> Sent: Wednesday, August 12, 2015 2:20 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 Wed, 12 Aug 2015, "Yang, Libin" <libin.yang at intel.com> wrote:
> > Hi Jani,
> >
> >> -----Original Message-----
> >> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
> >> Sent: Tuesday, August 11, 2015 4:14 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 Tue, 11 Aug 2015, "Yang, Libin" <libin.yang at intel.com> wrote:
> >> > Hi Jani,
> >> >
> >> >> -----Original Message-----
> >> >> From: Jani Nikula [mailto:jani.nikula at linux.intel.com]
> >> >> Sent: Tuesday, August 11, 2015 3:14 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 Tue, 11 Aug 2015, "Yang, Libin" <libin.yang at intel.com> wrote:
> >> >> > 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.
> >> >>
> >> >> Why does the audio driver not do anything here? Whenever
> there's
> >> a
> >> >> modeset, the graphics driver will disable audio and invalidate the
> >> ELD,
> >> >> which should cause an interrupt to notify the audio driver about
> >> >> this. This is no different from a hot-unplug, in fact I can't see how
> >> >> the audio driver could even detect whether there's been a
> hotplug
> >> or
> >> >> not
> >> >> when there's a codec disable/enable.
> >> >
> >> > Yes, it will trigger an interrupt to audio driver when unplug
> >> > and another interrupt for hotplug. But from audio driver,
> >> > we will not stop the playing and resume the playing based
> >> > on the hotplug or modeset. The audio is always playing during
> >> > the hotplug/modeset.
> >>
> >> But the whole display, and consequently ELD, might have changed
> >> during
> >> the hotplug, why do you assume you can just keep playing?! The
> >> display
> >> might even have changed from HDMI to DP or vice versa.
> >
> > The eld info changing will not impact the audio playing.
> > Actually, you can image the monitor as a digital speaker, just
> > like the headphone to the analog audio. Unplug the speaker
> > will not impact on the audio playing. Of course , there is a
> > little difference, when monitor hotplug, in the interrupt,
> > we may change the codec configuration dynamically.
> >
> > And audio driver supply the mechanism to stop the
> > audio playing when hotplug if the HW requires.
> >
> >>
> >> We've also been putting a lot of effort into not depending on
> previous
> >> state when enabling the outputs, for more reliability. We generally
> >> don't do partial changes, we disable everything and then enable
> >> again. And now you're suggesting we look at some register which for
> all
> >> we know may have been valid for some other display?
> >
> > In the patch, it will not depend on previous state, I think. We
> > read the register value which is based on the state after modeset.
> 
> Okay, let's have the patches cleaned up and see. It'll be easier and
> quicker to solicit more review on that than this expanding thread.

OK. Thanks.

> 
> Please find one more code comment below.
> 
> >
> >>
> >> Timeout.
> >>
> >>
> >> BR,
> >> Jani.
> >>
> >>
> >> >
> >> >>
> >> >> BR,
> >> >> Jani.
> >> >>
> >> >>
> >> >> >
> >> >> >>
> >> >> >> 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))) {
> 
> Please abstract that condition into a helper and give it a helpful
> name. That's repeated many times now, in this and negated forms, and
> I
> want the compiler to ensure it's the same in each place.

OK. I will do it.

> 
> Thanks,
> Jani.
> 
> >> >> >> > +		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
> >> >>
> >> >> --
> >> >> Jani Nikula, Intel Open Source Technology Center
> >>
> >> --
> >> Jani Nikula, Intel Open Source Technology Center
> 
> --
> Jani Nikula, Intel Open Source Technology Center

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