[PATCH 1/3] drm/i915/pps: Add helpers to lock PPS for AUX transfers
Imre Deak
imre.deak at intel.com
Mon Mar 24 14:04:36 UTC 2025
On Mon, Mar 24, 2025 at 03:59:50PM +0200, Jani Nikula wrote:
> On Mon, 24 Mar 2025, Imre Deak <imre.deak at intel.com> wrote:
> > On Mon, Mar 24, 2025 at 02:28:35PM +0200, Jani Nikula wrote:
> >> On Mon, 24 Mar 2025, Imre Deak <imre.deak at intel.com> wrote:
> >> > On Mon, Mar 24, 2025 at 12:33:22PM +0200, Jani Nikula wrote:
> >> >> On Fri, 21 Mar 2025, Imre Deak <imre.deak at intel.com> wrote:
> >> >> > Factor out from the DP AUX transfer function the logic to lock/unlock
> >> >> > the Panel Power Sequencer state and enable/disable the VDD power
> >> >> > required for the AUX transfer, adding these to helpers in intel_pps.c .
> >> >> > This prepares for a follow-up change making these steps dependent on the
> >> >> > platform and output type.
> >> >> >
> >> >> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> >> >> > ---
> >> >> > drivers/gpu/drm/i915/display/intel_dp_aux.c | 16 ++----------
> >> >> > drivers/gpu/drm/i915/display/intel_pps.c | 29 ++++++++++++++++++++-
> >> >> > drivers/gpu/drm/i915/display/intel_pps.h | 3 ++-
> >> >> > 3 files changed, 32 insertions(+), 16 deletions(-)
> >> >> >
> >> >> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> >> >> > index ec27bbd70bcf0..bf5ccfa24ca0b 100644
> >> >> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> >> >> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> >> >> > @@ -272,15 +272,7 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> >> >> > aux_domain = intel_aux_power_domain(dig_port);
> >> >> >
> >> >> > aux_wakeref = intel_display_power_get(display, aux_domain);
> >> >> > - pps_wakeref = intel_pps_lock(intel_dp);
> >> >> > -
> >> >> > - /*
> >> >> > - * We will be called with VDD already enabled for dpcd/edid/oui reads.
> >> >> > - * In such cases we want to leave VDD enabled and it's up to upper layers
> >> >> > - * to turn it off. But for eg. i2c-dev access we need to turn it on/off
> >> >> > - * ourselves.
> >> >> > - */
> >> >> > - vdd = intel_pps_vdd_on_unlocked(intel_dp);
> >> >> > + pps_wakeref = intel_pps_lock_for_aux(intel_dp, &vdd);
> >> >> >
> >> >> > /*
> >> >> > * dp aux is extremely sensitive to irq latency, hence request the
> >> >> > @@ -289,8 +281,6 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> >> >> > */
> >> >> > cpu_latency_qos_update_request(&intel_dp->pm_qos, 0);
> >> >> >
> >> >> > - intel_pps_check_power_unlocked(intel_dp);
> >> >> > -
> >> >> > /*
> >> >> > * FIXME PSR should be disabled here to prevent
> >> >> > * it using the same AUX CH simultaneously
> >> >> > @@ -427,10 +417,8 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> >> >> > out:
> >> >> > cpu_latency_qos_update_request(&intel_dp->pm_qos, PM_QOS_DEFAULT_VALUE);
> >> >> >
> >> >> > - if (vdd)
> >> >> > - intel_pps_vdd_off_unlocked(intel_dp, false);
> >> >> > + intel_pps_unlock_for_aux(intel_dp, pps_wakeref, vdd);
> >> >> >
> >> >> > - intel_pps_unlock(intel_dp, pps_wakeref);
> >> >> > intel_display_power_put_async(display, aux_domain, aux_wakeref);
> >> >> > out_unlock:
> >> >> > intel_digital_port_unlock(encoder);
> >> >> > diff --git a/drivers/gpu/drm/i915/display/intel_pps.c b/drivers/gpu/drm/i915/display/intel_pps.c
> >> >> > index 617ce49931726..3c078fd53fbfa 100644
> >> >> > --- a/drivers/gpu/drm/i915/display/intel_pps.c
> >> >> > +++ b/drivers/gpu/drm/i915/display/intel_pps.c
> >> >> > @@ -571,7 +571,7 @@ static bool edp_have_panel_vdd(struct intel_dp *intel_dp)
> >> >> > return intel_de_read(display, _pp_ctrl_reg(intel_dp)) & EDP_FORCE_VDD;
> >> >> > }
> >> >> >
> >> >> > -void intel_pps_check_power_unlocked(struct intel_dp *intel_dp)
> >> >> > +static void intel_pps_check_power_unlocked(struct intel_dp *intel_dp)
> >> >> > {
> >> >> > struct intel_display *display = to_intel_display(intel_dp);
> >> >> > struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> >> >> > @@ -955,6 +955,33 @@ void intel_pps_vdd_off(struct intel_dp *intel_dp)
> >> >> > intel_pps_vdd_off_unlocked(intel_dp, false);
> >> >> > }
> >> >> >
> >> >> > +intel_wakeref_t intel_pps_lock_for_aux(struct intel_dp *intel_dp, bool *vdd_ref)
> >> >> > +{
> >> >> > + intel_wakeref_t wakeref;
> >> >> > +
> >> >> > + wakeref = intel_pps_lock(intel_dp);
> >> >> > +
> >> >> > + /*
> >> >> > + * We will be called with VDD already enabled for dpcd/edid/oui reads.
> >> >> > + * In such cases we want to leave VDD enabled and it's up to upper layers
> >> >> > + * to turn it off. But for eg. i2c-dev access we need to turn it on/off
> >> >> > + * ourselves.
> >> >> > + */
> >> >> > + *vdd_ref = intel_pps_vdd_on_unlocked(intel_dp);
> >> >> > +
> >> >> > + intel_pps_check_power_unlocked(intel_dp);
> >> >> > +
> >> >> > + return wakeref;
> >> >> > +}
> >> >> > +
> >> >> > +void intel_pps_unlock_for_aux(struct intel_dp *intel_dp, intel_wakeref_t wakeref, bool vdd_ref)
> >> >> > +{
> >> >> > + if (vdd_ref)
> >> >> > + intel_pps_vdd_off_unlocked(intel_dp, false);
> >> >> > +
> >> >> > + intel_pps_unlock(intel_dp, wakeref);
> >> >> > +}
> >> >>
> >> >> It took me a while to pinpoint what exactly I don't like about this
> >> >> interface.
> >> >>
> >> >> And I mean the whole intel_pps.h interface is already really difficult
> >> >> to understand.
> >> >>
> >> >> This flips the lock/unlock and vdd on/off logic inside out.
> >> >>
> >> >> Normally you have functions for doing vdd or power or backlight, or
> >> >> anything PPS really, and they're either unlocked (assuming the caller
> >> >> handles PPS lock) or locked (the function itself takes the lock).
> >> >
> >> > The PPS and VDD handling steps are dependent (PPS must be locked for
> >> > enabling VDD) and both are skipped for the same reason during AUX
> >> > transfers. So I thought it makes sense to move these to a separate
> >> > function and skip both based on the same platform/output type check.
> >>
> >> On the contrary, I think the reasons are different.
> >>
> >> VDD is only needed for eDP.
> >>
> >> The PPS must be locked for VDD change (IOW for eDP) and for VLV/CHV pipe
> >> based PPS. But these two cases are independent.
> >
> > The case requiring VDD (eDP) is a subset of the cases requring PPS to be
> > locked (eDP or VLV/CHV). These are not independent cases.
>
> Logically, they are. VLV/CHV requires the PPS lock also for
> non-eDP.
Yes, that is what I meant.
1. Cases needing PPS lock: eDP or non-eDP on VLV/CHV.
2. Case needing VDD: eDP.
2. is a subset of 1.
> It's not a subset.
>
> BR,
> Jani.
>
>
>
> >
> >> >> This one purports to be an interface for lock/unlock, but in reality it
> >> >> also does VDD internally. And that feels really quite wrong to me.
> >> >>
> >> >> ---
> >> >>
> >> >> These are a single-use interface that I think make intel_pps.[ch] more
> >> >> difficult to understand. I'd suggest checking how you'd implement this
> >> >> logic inside intel_dp_aux_xfer() *without* changing the intel_pps.[ch]
> >> >> interface at all.
> >> >>
> >> >> Okay, took a quick stab at it, and unless I'm missing something it's
> >> >> super easy:
> >> >
> >> > I still think it'd be better to have a separate function for both
> >> > locking PPS and enabling VDD for the reason I described above, that is
> >> > to clarify that the PPS state must be locked to enable VDD.
> >>
> >> But there's no requirement that they must be done at the same time.
> >
> > There is also no reason not do them at the same time for AUX. A benefit
> > of doing that would be to clarify the dependency of VDD on PPS and also
> > simplify intel_dp_aux_xfer().
> >
> >> The PPS lock could be held for a much longer period or for other
> >> things than just VDD. And in this case, the PPS lock may indeed
> >> protect *other* things than just VDD. Adding the separate function
> >> ties these unrelated cases together for IMO not good enough reason.
> >> intel_pps_vdd_on_unlocked() does check that it's called with the PPS
> >> lock held.
> >>
> >> But I realize it needs to be relaxed a bit like this:
> >
> > Yes, noticed this too. It was one reason I opted for skipping PPS
> > locking / VDD enabling from one spot.
> >
> >> diff --git a/drivers/gpu/drm/i915/display/intel_pps.c b/drivers/gpu/drm/i915/display/intel_pps.c
> >> index 617ce4993172..c883e872c9c8 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_pps.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_pps.c
> >> @@ -744,11 +744,11 @@ bool intel_pps_vdd_on_unlocked(struct intel_dp *intel_dp)
> >> i915_reg_t pp_stat_reg, pp_ctrl_reg;
> >> bool need_to_disable = !intel_dp->pps.want_panel_vdd;
> >>
> >> - lockdep_assert_held(&display->pps.mutex);
> >> -
> >> if (!intel_dp_is_edp(intel_dp))
> >> return false;
> >>
> >> + lockdep_assert_held(&display->pps.mutex);
> >> +
> >> cancel_delayed_work(&intel_dp->pps.panel_vdd_work);
> >> intel_dp->pps.want_panel_vdd = true;
> >>
> >> @@ -925,11 +925,11 @@ void intel_pps_vdd_off_unlocked(struct intel_dp *intel_dp, bool sync)
> >> {
> >> struct intel_display *display = to_intel_display(intel_dp);
> >>
> >> - lockdep_assert_held(&display->pps.mutex);
> >> -
> >> if (!intel_dp_is_edp(intel_dp))
> >> return;
> >>
> >> + lockdep_assert_held(&display->pps.mutex);
> >> +
> >> INTEL_DISPLAY_STATE_WARN(display, !intel_dp->pps.want_panel_vdd,
> >> "[ENCODER:%d:%s] %s VDD not forced on",
> >> dp_to_dig_port(intel_dp)->base.base.base.id,
> >>
> >>
> >> > I guess the above could be done separately later in any case, so I can
> >> > inline the fix as you suggest.
> >> >
> >> >> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> >> >> index ec27bbd70bcf..a5608659df59 100644
> >> >> --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> >> >> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> >> >> @@ -247,7 +247,7 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> >> >> u32 aux_clock_divider;
> >> >> enum intel_display_power_domain aux_domain;
> >> >> intel_wakeref_t aux_wakeref;
> >> >> - intel_wakeref_t pps_wakeref;
> >> >> + intel_wakeref_t pps_wakeref = NULL;
> >> >> int i, ret, recv_bytes;
> >> >> int try, clock = 0;
> >> >> u32 status;
> >> >> @@ -272,7 +272,10 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> >> >> aux_domain = intel_aux_power_domain(dig_port);
> >> >>
> >> >> aux_wakeref = intel_display_power_get(display, aux_domain);
> >> >> - pps_wakeref = intel_pps_lock(intel_dp);
> >> >> +
> >> >> + if (intel_dp_is_edp(intel_dp) ||
> >> >> + (display->platform.valleyview || display->platform.cherryview))
> >> >> + pps_wakeref = intel_pps_lock(intel_dp);
> >> >>
> >> >> /*
> >> >> * We will be called with VDD already enabled for dpcd/edid/oui reads.
> >> >> @@ -430,7 +433,8 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> >> >> if (vdd)
> >> >> intel_pps_vdd_off_unlocked(intel_dp, false);
> >> >>
> >> >> - intel_pps_unlock(intel_dp, pps_wakeref);
> >> >> + if (pps_wakeref)
> >> >> + intel_pps_unlock(intel_dp, pps_wakeref);
> >> >> intel_display_power_put_async(display, aux_domain, aux_wakeref);
> >> >> out_unlock:
> >> >> intel_digital_port_unlock(encoder);
> >> >>
> >> >>
> >> >> Please let's not make intel_pps.[ch] harder to understand.
> >> >>
> >> >>
> >> >> BR,
> >> >> Jani.
> >> >>
> >> >>
> >> >> > +
> >> >> > void intel_pps_on_unlocked(struct intel_dp *intel_dp)
> >> >> > {
> >> >> > struct intel_display *display = to_intel_display(intel_dp);
> >> >> > diff --git a/drivers/gpu/drm/i915/display/intel_pps.h b/drivers/gpu/drm/i915/display/intel_pps.h
> >> >> > index c83007152f07d..4390d05892325 100644
> >> >> > --- a/drivers/gpu/drm/i915/display/intel_pps.h
> >> >> > +++ b/drivers/gpu/drm/i915/display/intel_pps.h
> >> >> > @@ -31,10 +31,11 @@ bool intel_pps_vdd_on_unlocked(struct intel_dp *intel_dp);
> >> >> > void intel_pps_vdd_off_unlocked(struct intel_dp *intel_dp, bool sync);
> >> >> > void intel_pps_on_unlocked(struct intel_dp *intel_dp);
> >> >> > void intel_pps_off_unlocked(struct intel_dp *intel_dp);
> >> >> > -void intel_pps_check_power_unlocked(struct intel_dp *intel_dp);
> >> >> >
> >> >> > void intel_pps_vdd_on(struct intel_dp *intel_dp);
> >> >> > void intel_pps_vdd_off(struct intel_dp *intel_dp);
> >> >> > +intel_wakeref_t intel_pps_lock_for_aux(struct intel_dp *intel_dp, bool *vdd_ref);
> >> >> > +void intel_pps_unlock_for_aux(struct intel_dp *intel_dp, intel_wakeref_t wakeref, bool vdd_ref);
> >> >> > void intel_pps_on(struct intel_dp *intel_dp);
> >> >> > void intel_pps_off(struct intel_dp *intel_dp);
> >> >> > void intel_pps_vdd_off_sync(struct intel_dp *intel_dp);
> >> >>
> >> >> --
> >> >> Jani Nikula, Intel
> >>
> >> --
> >> Jani Nikula, Intel
>
> --
> Jani Nikula, Intel
More information about the Intel-xe
mailing list