On Wed, 12 Feb 2020, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > Currently when we load the driver we set distrust_bios_wm=true, which > will cause active_pipe_changes to get flagged even when we're not > toggling any pipes on/off. The reason being that we want to fully > redistribute the dbuf among the active pipes and ignore whatever > state the firmware left behind. > > Unfortunately when the code flags active_pipe_changes it doesn't > set state->modeset to true, which means the hardware dbuf state > won't actually get updated. Hence the hardware and software > states go out of sync, which can result in planes trying to use a > disabled dbuf slice. Suprisingly that only seems to corrupt the > display rather than making the whole display engine keel over. > > Let's fix this for now by flagging state->modeset whenever > distrust_bios_wm is set. > > Eventually we'll likely want to rip out all of this mess and > introduce proper statye tracking for dbuf. But that requires > more work. Toss in a FIXME to that effect. I have a hard time following all the implications of this change. Would this under some circumstances lead to a case where we use the state read at probe, and do a full modeset on that state? DSC, lacking full state readout, fails badly with this change [1]. We'll do DSC enable using a mostly zeroed out DSC config in state. Leading to division by zero. BR, Jani. [1] https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16544/fi-tgl-dsi/boot0.txt > > Cc: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx> > Fixes: ff2cd8635e41 ("drm/i915: Correctly map DBUF slices to pipes") > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/display/intel_display.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > index 61ba1f2256a0..9e4f99ae81fb 100644 > --- a/drivers/gpu/drm/i915/display/intel_display.c > +++ b/drivers/gpu/drm/i915/display/intel_display.c > @@ -15027,6 +15027,20 @@ static int intel_atomic_check(struct drm_device *dev, > if (new_cdclk_state && new_cdclk_state->force_min_cdclk_changed) > any_ms = true; > > + /* > + * distrust_bios_wm will force a full dbuf recomputation > + * but the hardware state will only get updated accordingly > + * if state->modeset==true. Hence distrust_bios_wm==true && > + * state->modeset==false is an invalid combination which > + * would cause the hardware and software dbuf state to get > + * out of sync. We must prevent that. > + * > + * FIXME clean up this mess and introduce better > + * state tracking for dbuf. > + */ > + if (dev_priv->wm.distrust_bios_wm) > + any_ms = true; > + > if (any_ms) { > ret = intel_modeset_checks(state); > if (ret) -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
