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

Yang, Libin
2015-08-12T14:48:32Z

Hi Jani,

> -----Original Message-----
> From: Jani Nikula [mailto:jani.nikula@linux.intel.com]
> Sent: Wednesday, August 12, 2015 10:45 PM
> To: Yang, Libin; Daniel Vetter
> Cc: 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 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.

In another patch, we may not care the register value,
we need get_power to trigger an interrupt to audio
for the hotplug. Otherwise audio driver will never
receive the interrupt. After the interrupt is triggered,
we may not care the registers. This is a draft thought,
I need do more testing for that bug. Let's discuss about
it in another patch thread :)

Regards,
Libin

>
> BR,
> Jani.
>
>
>
> >
> > Regards,
> > Libin
> >
> >> -Daniel
> >> --
> >> Daniel Vetter
> >> Software Engineer, Intel Corporation
> >> http://blog.ffwll.ch
>
> --
> Jani Nikula, Intel Open Source Technology Center