On Fri, Nov 05, 2021 at 05:44:21PM +0000, Souza, Jose wrote:
> On Fri, 2021-11-05 at 15:46 +0200, Ville Syrjälä wrote:
> > On Thu, Nov 04, 2021 at 05:56:52PM +0000, Souza, Jose wrote:
> > > On Thu, 2021-11-04 at 16:10 +0200, Ville Syrjälä wrote:
> > > > On Tue, Nov 02, 2021 at 12:32:14PM -0700, José Roberto de Souza wrote:
> > > > > Changing the buffer in the middle of the scanout then entering an
> > > > > period of flip idleness will cause part of the previous buffer being
> > > > > diplayed to user when PSR is enabled.
> > > > >
> > > > > So here disabling PSR and scheduling activation during the next
> > > > > sync flip.
> > > > >
> > > > > The async flip check that we had in PSR compute is not executed at
> > > > > every flip so it was not doing anything useful and is also being
> > > > > dropped here.
> > > > >
> > > > > v2:
> > > > > - scheduling the PSR work in _intel_psr_post_plane_update()
> > > > >
> > > > > v3:
> > > > > - only re enabling PSR when doing a sync flip
> > > > >
> > > > > Cc: Karthik B S <karthik....@intel.com>
> > > > > Cc: Vandita Kulkarni <vandita.kulka...@intel.com>
> > > > > Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> > > > > Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
> > > > > Signed-off-by: José Roberto de Souza <jose.so...@intel.com>
> > > > > ---
> > > > > drivers/gpu/drm/i915/display/intel_psr.c | 37
> > > > > ++++++++++++++----------
> > > > > 1 file changed, 21 insertions(+), 16 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > b/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > index 9d589d471e335..b8fac53d57df1 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > > > > @@ -731,12 +731,6 @@ static bool
> > > > > intel_psr2_sel_fetch_config_valid(struct intel_dp *intel_dp,
> > > > > return false;
> > > > > }
> > > > >
> > > > > - if (crtc_state->uapi.async_flip) {
> > > > > - drm_dbg_kms(&dev_priv->drm,
> > > > > - "PSR2 sel fetch not enabled, async flip
> > > > > enabled\n");
> > > > > - return false;
> > > > > - }
> > > > > -
> > > > > /* Wa_14010254185 Wa_14010103792 */
> > > > > if (IS_TGL_DISPLAY_STEP(dev_priv, STEP_A0, STEP_C0)) {
> > > > > drm_dbg_kms(&dev_priv->drm,
> > > > > @@ -1780,36 +1774,47 @@ void intel_psr_pre_plane_update(struct
> > > > > intel_atomic_state *state,
> > > > > if (psr->enabled && needs_to_disable)
> > > > > intel_psr_disable_locked(intel_dp);
> > > > >
> > > > > + if (psr->enabled && crtc_state->uapi.async_flip)
> > > > > + intel_psr_exit(intel_dp);
> > > > > +
> > > > > mutex_unlock(&psr->lock);
> > > > > }
> > > > > }
> > > > >
> > > > > static void _intel_psr_post_plane_update(const struct
> > > > > intel_atomic_state *state,
> > > > > - const struct intel_crtc_state
> > > > > *crtc_state)
> > > > > + const struct intel_crtc_state
> > > > > *old_crtc_state,
> > > > > + const struct intel_crtc_state
> > > > > *new_crtc_state)
> > > >
> > > > Might make sense to change this to match how psr_pre_plane_update()
> > > > works these days.
> > >
> > > Will do as follow up.
> > >
> > > >
> > > > > {
> > > > > struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> > > > > struct intel_encoder *encoder;
> > > > >
> > > > > - if (!crtc_state->has_psr)
> > > > > + if (!new_crtc_state->has_psr)
> > > > > return;
> > > > >
> > > > > for_each_intel_encoder_mask_with_psr(state->base.dev, encoder,
> > > > > -
> > > > > crtc_state->uapi.encoder_mask) {
> > > > > +
> > > > > new_crtc_state->uapi.encoder_mask) {
> > > > > struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > > > > struct intel_psr *psr = &intel_dp->psr;
> > > > >
> > > > > mutex_lock(&psr->lock);
> > > > >
> > > > > - drm_WARN_ON(&dev_priv->drm, psr->enabled &&
> > > > > !crtc_state->active_planes);
> > > > > + drm_WARN_ON(&dev_priv->drm, psr->enabled &&
> > > > > + !new_crtc_state->active_planes);
> > > > >
> > > > > /* Only enable if there is active planes */
> > > > > - if (!psr->enabled && crtc_state->active_planes)
> > > > > - intel_psr_enable_locked(intel_dp, crtc_state);
> > > > > + if (!psr->enabled && new_crtc_state->active_planes)
> > > > > + intel_psr_enable_locked(intel_dp,
> > > > > new_crtc_state);
> > > >
> > > > What prevents this guy from activating PSR while we're doing
> > > > an async flip?
> > >
> > > enabled != active, when doing a async flip it will set active = false but
> > > enabled will be kept on.
> >
> > intel_psr_enable_locked() calls intel_psr_activate() uncoditionally.
> > There is no active=false thing anywhere that I can see.
> >
> > >
> > > And to change the number of active_planes it will need to do a sync flip,
> > > so we are safe.
> >
> > Why would the number of active planes need to change for this
> > to get called?
>
> If CRTC is left on but the number of planes goes to 0, PSR is disabled.
> Then it is enabled again if the number of planes goes to 1 or more.
>
> >
> > I guess maybe there's some reason why this can't happen but it is
> > entirely non-obvious when reading this code. Also seems pretty
> > fragile if some other code now changes and suddenly causes this
> > to get called. In fact from the looks of things the only thing
> > needed would be for someone to call intel_psr_disable_locked()
> > so that psr->enabled gets cleared.
>
> If someone calls intel_psr_disable_locked() then in the next flip the code
> above will indeed enable it again but as PSR takes at least 2 frames to
> actually activate after registers are programmed, we are safe. (see PSR2
> EDP_PSR2_FRAME_BEFORE_SU and PSR1 psr_compute_idle_frames())
>
> Then on the next async flip, it will exited again and active set to false.
>
> >
> > I might suggest adding crtc_state->psr_active or soemthing along
> > those lines to make it obvious when we want to have psr logically
> > enabled, but actually inactive.
>
> Because of the invalidate frontbuffer rendering cases, we can't keep PSR
> status in atomic state.
Not fully. But it shouldn't prevent us from having something there as
well. So if crtc_state says to not activate PSR then don't, otherwise
let it activate/deactive as needed based on frontbuffer activity.
ATM it seems to be kind of ad-hoc when we fully disable vs. just
deactivate PSR. Dunno how feasible it would be to make that either:
a) logically enable/disable PSR only during full modesets, and
otherwise just activate/deactivate as needed whether it be due to
stuff we can calculate based on crtc_state (eg. active_planes or
async_flip) or frontbuffer activity
or
b) always logically enable/disable PSR based on stuff we can calculate
from the crtc state, and leave the activate/deactivate stuff to only
frontbuffer rendering activity
Although there is also the AUX vs. PSR case to consider, but looks like
that is still not fixed.
--
Ville Syrjälä
Intel
