On Tue, 2021-02-16 at 18:00 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> Populate conn_state->max_bpc with something sensible from the start.
> Otherwise it's possible that we get to compute_sink_pipe_bpp() with
> max_bpc==0.
>
> The specific scenario goes as follows:
> 1. Initial connector state allocated with max_bpc==0
> 2. Trigger a modeset on the crtc feeding the connector, without
> actually adding the connector to the commit
> 3. drm_atomic_connector_check() is skipped because the
> connector has not yet been added, hence conn_state->max_bpc
> retains its current value
> 4. drm_atomic_helper_check_modeset() ->
> drm_atomic_add_affected_connectors() -> the connector
> is now part of the commit
> 5. compute_baseline_pipe_bpp() -> MISSING_CASE(max_bpc==0)
>
> Note that pipe_bpp itself may not be populated on pre-g4x machines,
> in which case we just fall back to max_bpc==8 and let .compute_config()
> limit the resulting pipe_bpp further if necessary.
Reviewed-by: José Roberto de Souza <jose.souza@xxxxxxxxx>
>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Reported-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_display.c | 24 +++++++++++++-------
> 1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 0dc5cb36667a..4d63e68a5ea2 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -7987,19 +7987,27 @@ static void intel_modeset_update_connector_atomic_state(struct drm_device *dev)
>
>
>
>
> drm_connector_list_iter_begin(dev, &conn_iter);
> for_each_intel_connector_iter(connector, &conn_iter) {
> - if (connector->base.state->crtc)
> + struct drm_connector_state *conn_state = connector->base.state;
> + struct intel_encoder *encoder =
> + to_intel_encoder(connector->base.encoder);
> +
> + if (conn_state->crtc)
> drm_connector_put(&connector->base);
>
>
>
>
> - if (connector->base.encoder) {
> - connector->base.state->best_encoder =
> - connector->base.encoder;
> - connector->base.state->crtc =
> - connector->base.encoder->crtc;
> + if (encoder) {
> + struct intel_crtc *crtc =
> + to_intel_crtc(encoder->base.crtc);
> + const struct intel_crtc_state *crtc_state =
> + to_intel_crtc_state(crtc->base.state);
> +
> + conn_state->best_encoder = &encoder->base;
> + conn_state->crtc = &crtc->base;
> + conn_state->max_bpc = (crtc_state->pipe_bpp ?: 24) / 3;
>
>
>
>
> drm_connector_get(&connector->base);
> } else {
> - connector->base.state->best_encoder = NULL;
> - connector->base.state->crtc = NULL;
> + conn_state->best_encoder = NULL;
> + conn_state->crtc = NULL;
> }
> }
> drm_connector_list_iter_end(&conn_iter);
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