On Thu, Feb 13, 2020 at 04:04:12PM +0200, Stanislav Lisovskiy 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.
>
> Cc: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> Fixes: ff2cd8635e41 ("drm/i915: Correctly map DBUF slices to pipes")
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
> ---
> 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 1e3f2cc27db8..df47b2fdfa38 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)
> --
> 2.24.1.485.gad05a3d8e5
>
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--
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
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