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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 12 Aug 2015, "Yang, Libin" <libin.yang@intel.com> wrote:
> Hi Daniel,
>
>> -----Original Message-----
>> From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of
>> Daniel Vetter
>> Sent: Wednesday, August 12, 2015 9:06 PM
>> To: Jani Nikula
>> Cc: Yang, Libin; alsa-devel@alsa-project.org; tiwai@suse.de; intel-
>> gfx@lists.freedesktop.org; daniel.vetter@ffwll.ch
>> Subject: Re: [Intel-gfx] [PATCH v2 2/4] drm/i915: implement set_ncts
>> callback
>> 
>> 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 ...
>
> Sorry, I'm not understanding your meaning clearly. 
> Do you mean if we put the power well, the register's value will
> be invalid? Actually, we found another issue for audio power
> management (this is another bug, not related to this feature),
> and I'm thinking to add get_power/put_power as Jani said
> in another patch.

No, the point was that you should rather check that we have power. If
there isn't, and you get/put, you'll lose the values at the put.

BR,
Jani.



>
> Regards,
> Libin
>
>> -Daniel
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch

-- 
Jani Nikula, Intel Open Source Technology Center
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