[PATCH 2/2] drm/i915/psr: Implment WA to help reach PC10

[Kandpal, Suraj]

> Subject: Re: [PATCH 2/2] drm/i915/psr: Implment WA to help reach PC10
> 
> On Thu, 06 Jun 2024, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> > To reach PC10 when PKG_C_LATENCY is configure we must do the following
> > things
> > 1) Enter PSR1 only when delayed_vblank < 6 lines and DC5 can be
> > entered
> > 2) Allow PSR2 deep sleep when DC5 can be entered
> > 3) DC5 can be entered when all transocoder have either PSR1, PSR2 or
> > eDP 1.5 PR ALPM enabled and VBI is disabled and flips and pushes are
> > not happening.
> >
> > WA: 16023497226
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_psr.c | 75
> > +++++++++++++++++++++++-
> >  1 file changed, 73 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > b/drivers/gpu/drm/i915/display/intel_psr.c
> > index 6fc88f6c6b26..b22745c019df 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > @@ -811,12 +811,81 @@ static u8 psr_compute_idle_frames(struct
> intel_dp *intel_dp)
> >  	return idle_frames;
> >  }
> >
> > +static bool intel_psr_check_delayed_vblank_limit(struct drm_i915_private
> *i915,
> > +						 enum transcoder
> cpu_transcoder) {
> > +	return intel_de_read(i915,
> > +TRANS_SET_CONTEXT_LATENCY(cpu_transcoder)) >= 6;
> 
Hi Jani,
Thanks for the reviews

> Please don't use the hardware to preserve the state for you. It will get really
> complicated to maintain.
> 

Yes wanted to calculate the delayed vblank using the following way
Adjusted_mode->vblank_start - adjusted_mode->vblank_end
But I'll need crtc_state for that and I don't see a way of deriving it
Specially when this function is called from intel_psr_work
One way could be to have this wa check function be called from 
Intel_psr_enable_locked and save the corresponding Booleans in
Intel_psr or make in  drm_i915_private
structure and access that when intel_psr_activate is called from
Intel_psr_resume and intel_psr_work.
Do you think that could be feasible ?

> > +}
> > +
> > +static bool intel_psr_is_dpkgc_configured(struct drm_i915_private
> > +*i915) {
> > +	return intel_de_read(i915, LNL_PKG_C_LATENCY) == U32_MAX;
> 
> Ditto.
> 

Similar question as above only place that I can manage a state to see if it is configured or not
would be in drm_i915_private.

> > +}
> > +
> > +static bool intel_psr_is_dc5_entry_possible(struct drm_i915_private
> > +*i915) {
> > +	struct intel_crtc *intel_crtc;
> > +	bool ret = true;
> > +
> > +	for_each_intel_crtc(&i915->drm, intel_crtc) {
> > +		struct intel_encoder *encoder;
> > +		struct drm_crtc *crtc = &intel_crtc->base;
> > +		enum pipe pipe = intel_crtc->pipe;
> > +
> > +		if (!crtc->active)
> > +			continue;
> > +
> > +		if (!(i915->display.irq.de_irq_mask[pipe] &
> GEN8_PIPE_VBLANK))
> 
> You have no business looking directly at that. It's for display irq code *only*.
> 

Is there another way I can ensure if the vblank interrupt for the particular pipe is disabled?

> > +			ret = false;
> > +
> > +		for_each_encoder_on_crtc(&i915->drm, crtc, encoder) {
> > +			struct intel_dp *intel_dp = enc_to_intel_dp(_encoder);
> > +			struct intel_psr *psr = &intel_dp->psr;
> > +
> > +			if (!psr->enabled)
> > +				ret = false;
> > +		}
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static bool wa_16023497226_check(struct intel_dp *intel_dp, bool
> > +psr1) {
> > +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > +	enum transcoder cpu_transcoder = intel_dp->psr.transcoder;
> > +
> > +	if (DISPLAY_VER(i915) != 20)
> > +		return true;
> > +
> > +	if (is_dpkg_c_configured(i915)) {
> > +		if (psr1 &&
> > +		    (intel_psr_check_delayed_vblank_limit(i915,
> cpu_transcoder) ||
> > +		     intel_psr_is_dc5_entry_possible(i915)))
> > +			return true;
> > +		else if (!psr1 && is_dc5_entry_possible(i915))
> > +			return true;
> > +		else
> > +			return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> >  static bool hsw_activate_psr1(struct intel_dp *intel_dp)  {
> >  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> >  	enum transcoder cpu_transcoder = intel_dp->psr.transcoder;
> >  	u32 max_sleep_time = 0x1f;
> > -	u32 val = EDP_PSR_ENABLE;
> > +	u32 val = 0;
> > +
> > +	/* WA: 16023497226*/
> > +	if (wa_16023497226_check(intel_dp, true)) {
> > +		val = EDP_PSR_ENABLE;
> > +	} else {
> > +		drm_dbg_kms(&dev_priv->drm, "PSR1 was not activated\n");
> 
> Please add reason.
> 
> > +		return false;
> > +	}
> 
> Switch the condition around and use early return.
> 

Sure will do.

Regards,
Suraj Kandpal
> >
> >  	val |= EDP_PSR_IDLE_FRAMES(psr_compute_idle_frames(intel_dp));
> >
> > @@ -910,7 +979,9 @@ static void hsw_activate_psr2(struct intel_dp
> *intel_dp)
> >  	u32 val = EDP_PSR2_ENABLE;
> >  	u32 psr_val = 0;
> >
> > -	val |= EDP_PSR2_IDLE_FRAMES(psr_compute_idle_frames(intel_dp));
> > +	/* WA: 16023497226*/
> > +	if (wa_16023497226_check(intel_dp, false))
> > +		val |=
> EDP_PSR2_IDLE_FRAMES(psr_compute_idle_frames(intel_dp));
> >
> >  	if (DISPLAY_VER(dev_priv) < 14 && !IS_ALDERLAKE_P(dev_priv))
> >  		val |= EDP_SU_TRACK_ENABLE;
> 
> --
> Jani Nikula, Intel