Re: [PATCH] drm/i915: Adjust eDP's logical vco in a reliable place.

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, May 02, 2018 at 10:12:51PM +0300, Ville Syrjälä wrote:
> On Wed, May 02, 2018 at 10:52:55AM -0700, Rodrigo Vivi wrote:
> > On intel_dp_compute_config() we were calculating the needed vco
> > for eDP on gen9 and we stashing it in
> > intel_atomic_state.cdclk.logical.vco
> > 
> > However few moments later on intel_modeset_checks() we fully
> > replace entire intel_atomic_state.cdclk.logical with
> > dev_priv->cdclk.logical fully overwriting the logical desired
> > vco for eDP on gen9.
> > 
> > So, with wrong VCO value we end up with wrong desired cdclk, but
> > also it will raise a lot of WARNs: On gen9, when we read
> > CDCLK_CTL to verify if we configured properly the desired
> > frequency the CD Frequency Select bits [27:26] == 10b can mean
> > 337.5 or 308.57 MHz depending on the VCO. So if we have wrong
> > VCO value stashed we will believe the frequency selection didn't
> > stick and start to raise WARNs of cdclk mismatch.
> > 
> > [   42.857519] [drm:intel_dump_cdclk_state [i915]] Changing CDCLK to 308571 kHz, VCO 8640000 kHz, ref 24000 kHz, bypass 24000 kHz, voltage level 0
> > [   42.897269] cdclk state doesn't match!
> > [   42.901052] WARNING: CPU: 5 PID: 1116 at drivers/gpu/drm/i915/intel_cdclk.c:2084 intel_set_cdclk+0x5d/0x110 [i915]
> > [   42.938004] RIP: 0010:intel_set_cdclk+0x5d/0x110 [i915]
> > [   43.155253] WARNING: CPU: 5 PID: 1116 at drivers/gpu/drm/i915/intel_cdclk.c:2084 intel_set_cdclk+0x5d/0x110 [i915]
> > [   43.170277] [drm:intel_dump_cdclk_state [i915]] [hw state] 337500 kHz, VCO 8100000 kHz, ref 24000 kHz, bypass 24000 kHz, voltage level 0
> > [   43.182566] [drm:intel_dump_cdclk_state [i915]] [sw state] 308571 kHz, VCO 8640000 kHz, ref 24000 kHz, bypass 24000 kHz, voltage level 0
> > 
> > v2: Move the entire eDP's vco logical adjustment to inside
> >     the skl_modeset_calc_cdclk as suggested by Ville.
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_cdclk.c | 41 ++++++++++++++++++++++++++++++++++----
> >  drivers/gpu/drm/i915/intel_dp.c    | 20 -------------------
> >  2 files changed, 37 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c
> > index 32d24c69da3c..704ddb4d3ca7 100644
> > --- a/drivers/gpu/drm/i915/intel_cdclk.c
> > +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> > @@ -2302,9 +2302,44 @@ static int bdw_modeset_calc_cdclk(struct drm_atomic_state *state)
> >  	return 0;
> >  }
> >  
> > +static int skl_dpll0_vco(struct intel_atomic_state *intel_state)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(intel_state->base.dev);
> > +	struct intel_crtc *crtc;
> > +	struct intel_crtc_state *crtc_state;
> > +	int vco, i;
> > +
> > +	vco = intel_state->cdclk.logical.vco;
> > +	if (!vco)
> > +		vco = dev_priv->skl_preferred_vco_freq;
> > +
> > +	for_each_new_intel_crtc_in_state(intel_state, crtc, crtc_state, i) {
> > +		if (!crtc_state->base.enable)
> > +			continue;
> > +
> > +		if (!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_EDP))
> > +			continue;
> > +
> > +		/*
> > +		 * DPLL0 VCO may need to be adjusted to get the correct
> > +		 * clock for eDP. This will affect cdclk as well.
> > +		 */
> > +		switch (crtc_state->port_clock / 2) {
> > +		case 108000:
> > +		case 216000:
> > +			vco = 8640000;
> > +			break;
> > +		default:
> > +			vco = 8100000;
> > +			break;
> > +		}
> > +	}
> > +
> > +	return vco;
> > +}
> 
> Yep. I think this should do the right thing. For the times when the pipe
> driving eDP isn't part of the atomic state we wil simply preserve the
> current vco setting. That means other pipes can't actually make a mess
> of the DPLL0 VCO while eDP depends on it.
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Thanks for the suggestions.

So, on setting the examples of what *not* to do: I forgot to include
Fixes: and cc stable.

Luckily I remembered before pushing. So,

Fixes: bb0f4aab0e76 ("drm/i915: Track full cdclk state for the logical and actual cdclk frequencies")
Cc: <stable@vger.kernel.org> # v4.12+

seems right for you?

> 
> > +
> >  static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
> >  {
> > -	struct drm_i915_private *dev_priv = to_i915(state->dev);
> >  	struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
> >  	int min_cdclk, cdclk, vco;
> >  
> > @@ -2312,9 +2347,7 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
> >  	if (min_cdclk < 0)
> >  		return min_cdclk;
> >  
> > -	vco = intel_state->cdclk.logical.vco;
> > -	if (!vco)
> > -		vco = dev_priv->skl_preferred_vco_freq;
> > +	vco = skl_dpll0_vco(intel_state);
> >  
> >  	/*
> >  	 * FIXME should also account for plane ratio
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 83da50b13d81..dde92e4af5d3 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1929,26 +1929,6 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> >  					       reduce_m_n);
> >  	}
> >  
> > -	/*
> > -	 * DPLL0 VCO may need to be adjusted to get the correct
> > -	 * clock for eDP. This will affect cdclk as well.
> > -	 */
> > -	if (intel_dp_is_edp(intel_dp) && IS_GEN9_BC(dev_priv)) {
> > -		int vco;
> > -
> > -		switch (pipe_config->port_clock / 2) {
> > -		case 108000:
> > -		case 216000:
> > -			vco = 8640000;
> > -			break;
> > -		default:
> > -			vco = 8100000;
> > -			break;
> > -		}
> > -
> > -		to_intel_atomic_state(pipe_config->base.state)->cdclk.logical.vco = vco;
> > -	}
> > -
> >  	if (!HAS_DDI(dev_priv))
> >  		intel_dp_set_clock(encoder, pipe_config);
> >  
> > -- 
> > 2.13.6
> 
> -- 
> Ville Syrjälä
> Intel
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