Re: [PATCH v2 2/4] drm/i915: implement set_ncts callback

From: Daniel Vetter <daniel@ffwll.ch>
To: Jani Nikula <jani.nikula@linux.intel.com>
Cc: tiwai@suse.de, alsa-devel@alsa-project.org,
	intel-gfx@lists.freedesktop.org, daniel.vetter@ffwll.ch
Subject: Re: [PATCH v2 2/4] drm/i915: implement set_ncts callback
Date: Wed, 12 Aug 2015 15:06:17 +0200	[thread overview]
Message-ID: <20150812130617.GO17734@phenom.ffwll.local> (raw)
In-Reply-To: <87vbcn72z5.fsf@intel.com>

On Mon, Aug 10, 2015 at 03:16:46PM +0300, Jani Nikula wrote:
> On Mon, 10 Aug 2015, libin.yang@intel.com wrote:
> > From: Libin Yang <libin.yang@intel.com>
> >
> > Display audio may not work at some frequencies
> > with the HW provided N/CTS.
> >
> > This patch sets the proper N value for the
> > given audio sample rate at the impacted frequencies.
> > At other frequencies, it will use the N/CTS value
> > which HW provides.
> >
> > Signed-off-by: Libin Yang <libin.yang@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h    |  2 +
> >  drivers/gpu/drm/i915/intel_audio.c | 95 ++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 97 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index ea46d68..da2d128 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -7014,6 +7014,8 @@ enum skl_disp_power_wells {
> >  					_HSW_AUD_MISC_CTRL_A, \
> >  					_HSW_AUD_MISC_CTRL_B)
> >  
> > +#define HSW_AUD_PIPE_CONN_SEL_CTRL  0x650ac
> > +
> >  #define _HSW_AUD_DIP_ELD_CTRL_ST_A	0x650b4
> >  #define _HSW_AUD_DIP_ELD_CTRL_ST_B	0x651b4
> >  #define HSW_AUD_DIP_ELD_CTRL(pipe) _PIPE(pipe, \
> > diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
> > index dc32cf4..eddf37f 100644
> > --- a/drivers/gpu/drm/i915/intel_audio.c
> > +++ b/drivers/gpu/drm/i915/intel_audio.c
> > @@ -68,6 +68,30 @@ static const struct {
> >  	{ 148500, AUD_CONFIG_PIXEL_CLOCK_HDMI_148500 },
> >  };
> >  
> > +#define TMDS_297M 297000
> > +#define TMDS_296M DIV_ROUND_UP(297000 * 1000, 1001)
> > +static const struct {
> > +	int sample_rate;
> > +	int clock;
> > +	int n;
> > +	int cts;
> > +} aud_ncts[] = {
> > +	{ 44100, TMDS_296M, 4459, 234375 },
> > +	{ 44100, TMDS_297M, 4704, 247500 },
> > +	{ 48000, TMDS_296M, 5824, 281250 },
> > +	{ 48000, TMDS_297M, 5120, 247500 },
> > +	{ 32000, TMDS_296M, 5824, 421875 },
> > +	{ 32000, TMDS_297M, 3072, 222750 },
> > +	{ 88200, TMDS_296M, 8918, 234375 },
> > +	{ 88200, TMDS_297M, 9408, 247500 },
> > +	{ 96000, TMDS_296M, 11648, 281250 },
> > +	{ 96000, TMDS_297M, 10240, 247500 },
> > +	{ 176400, TMDS_296M, 17836, 234375 },
> > +	{ 176400, TMDS_297M, 18816, 247500 },
> > +	{ 44100, TMDS_296M, 23296, 281250 },
> > +	{ 44100, TMDS_297M, 20480, 247500 },
> > +};
> > +
> >  /* get AUD_CONFIG_PIXEL_CLOCK_HDMI_* value for mode */
> >  static u32 audio_config_hdmi_pixel_clock(struct drm_display_mode *mode)
> >  {
> > @@ -514,12 +538,83 @@ static int i915_audio_component_get_cdclk_freq(struct device *dev)
> >  	return ret;
> >  }
> >  
> > +static int i915_audio_component_set_ncts(struct device *dev, int port,
> > +			int dev_entry, int rate)
> > +{
> > +	struct drm_i915_private *dev_priv = dev_to_i915(dev);
> > +	struct drm_device *drm_dev = dev_priv->dev;
> > +	struct intel_encoder *intel_encoder;
> > +	struct intel_digital_port *intel_dig_port;
> > +	struct intel_crtc *crtc;
> > +	struct drm_display_mode *mode;
> > +	enum pipe pipe = -1;
> > +	u32 tmp;
> > +	int i;
> > +	int n_low, n_up, n = 0;
> 
> I think you'll need the power well get here, and put at the end. Or
> check that we it.

If we call this and end up actually dropping the power well then the
register writes will go exactly nowhere at all. Which indicates a bug in
how this is orchestrated. There is probably one ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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