On Thu, Apr 21, 2022 at 12:22:03PM -0700, José Roberto de Souza wrote: > Intel hardware supports change between modes with different refresh > rates without any glitches or visual artifacts, that feature is called > seamless DRRS. > > So far i915 driver was automatically changing between preferred panel > mode and lower refresh rate mode based on idleness but ChromeOS > compositor team is requesting to be in control of the mode switch. > So for a certain types of content it can switch to mode with a lower > refresh rate without user noticing a thing and saving power. > > This seamless mode switch will be triggered when user-space dispatch > a atomic commit with the new mode and clears the > DRM_MODE_ATOMIC_ALLOW_MODESET flag. > > A driver that don't implement atomic_seamless_mode_switch_check > function will continue to fail in the atomic check phase with > "[CRTC:%d:%s] requires full modeset" debug message. > While a driver that implements it and support the seamless change > between old and new mode will return 0 otherwise it should return the > appropried errno. > > So here adding basic drm infrastructure to that be supported by i915 > and other drivers. I don't see the need for any extra infrastructure for this. I think we just need: - fix the fastset code to not suck - reprogram M/N during fastset - calculate eDP link params using panel's highest refresh rate mode to make sure we get the same link params for all refresh rates > > Cc: Vidya Srinivas <vidya.srinivas@xxxxxxxxx> > Cc: Sean Paul <seanpaul@xxxxxxxxxxxx> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Signed-off-by: José Roberto de Souza <jose.souza@xxxxxxxxx> > --- > drivers/gpu/drm/drm_atomic.c | 1 + > drivers/gpu/drm/drm_atomic_helper.c | 16 +++++++++++++++ > drivers/gpu/drm/drm_atomic_state_helper.c | 1 + > include/drm/drm_crtc.h | 25 +++++++++++++++++++++++ > 4 files changed, 43 insertions(+) > > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c > index 58c0283fb6b0c..21525f9f4b4c1 100644 > --- a/drivers/gpu/drm/drm_atomic.c > +++ b/drivers/gpu/drm/drm_atomic.c > @@ -437,6 +437,7 @@ static void drm_atomic_crtc_print_state(struct drm_printer *p, > drm_printf(p, "\tself_refresh_active=%d\n", state->self_refresh_active); > drm_printf(p, "\tplanes_changed=%d\n", state->planes_changed); > drm_printf(p, "\tmode_changed=%d\n", state->mode_changed); > + drm_printf(p, "\tseamless_mode_changed=%d\n", state->seamless_mode_changed); > drm_printf(p, "\tactive_changed=%d\n", state->active_changed); > drm_printf(p, "\tconnectors_changed=%d\n", state->connectors_changed); > drm_printf(p, "\tcolor_mgmt_changed=%d\n", state->color_mgmt_changed); > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > index 9603193d2fa13..e6f3a966f7b86 100644 > --- a/drivers/gpu/drm/drm_atomic_helper.c > +++ b/drivers/gpu/drm/drm_atomic_helper.c > @@ -631,6 +631,22 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, > drm_dbg_atomic(dev, "[CRTC:%d:%s] mode changed\n", > crtc->base.id, crtc->name); > new_crtc_state->mode_changed = true; > + > + if (!state->allow_modeset && > + crtc->funcs->atomic_seamless_mode_switch_check) { > + ret = crtc->funcs->atomic_seamless_mode_switch_check(state, crtc); > + if (ret == -EOPNOTSUPP) { > + drm_dbg_atomic(dev, "[CRTC:%d:%s] Seamless mode switch not supported\n", > + crtc->base.id, crtc->name); > + return ret; > + } > + > + if (ret < 0) > + return ret; > + > + new_crtc_state->seamless_mode_changed = true; > + new_crtc_state->mode_changed = false; > + } > } > > if (old_crtc_state->enable != new_crtc_state->enable) { > diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c > index 3b6d3bdbd0996..c093073ea6e11 100644 > --- a/drivers/gpu/drm/drm_atomic_state_helper.c > +++ b/drivers/gpu/drm/drm_atomic_state_helper.c > @@ -142,6 +142,7 @@ void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc, > if (state->gamma_lut) > drm_property_blob_get(state->gamma_lut); > state->mode_changed = false; > + state->seamless_mode_changed = false; > state->active_changed = false; > state->planes_changed = false; > state->connectors_changed = false; > diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h > index a70baea0636ca..b7ce378d679d3 100644 > --- a/include/drm/drm_crtc.h > +++ b/include/drm/drm_crtc.h > @@ -140,6 +140,16 @@ struct drm_crtc_state { > */ > bool mode_changed : 1; > > + /** > + * @seamless_mode_changed: @mode has been changed but user-space > + * is requesting to change to the new mode with a fastset and driver > + * supports this request. > + * To be used by drivers to steer the atomic commit control flow to > + * appropriate paths to change mode without any visual corruption. > + * Never set together with @mode_changed. > + */ > + bool seamless_mode_changed : 1; > + > /** > * @active_changed: @active has been toggled. Used by the atomic > * helpers and drivers to steer the atomic commit control flow. See also > @@ -939,6 +949,21 @@ struct drm_crtc_funcs { > int *max_error, > ktime_t *vblank_time, > bool in_vblank_irq); > + > + /** > + * @atomic_seamless_mode_switch_check > + * > + * Called when user-space wants to change mode without do a modeset. > + * Drivers can optionally support do a mode switch without any visual > + * corruption when changing between certain modes. > + * > + * Returns: > + * Zero if possible to seamless switch mode, -EOPNOTSUPP if not > + * supported seamless mode change or appropriate errno if an error > + * happened. > + */ > + int (*atomic_seamless_mode_switch_check)(struct drm_atomic_state *state, > + struct drm_crtc *crtc); > }; > > /** > -- > 2.36.0 -- Ville Syrjälä Intel