From: Dom Cobley popcornmix@gmail.com
Whenever the maximum BPC is changed, vc4_hdmi_encoder_compute_config() might pick up a different BPC or format depending on the display capabilities.
That change will have a number of side effects, including the clock rates and whether the scrambling is enabled.
However, only drm_crtc_state.connectors_changed will be set to true, since that properly only affects the connector.
This means that while drm_atomic_crtc_needs_modeset() will return true, and thus drm_atomic_helper_commit_modeset_enables() will call our encoder atomic_enable() hook, mode_changed will be false.
So crtc_set_mode() will not call our encoder .atomic_mode_set() hook. We use this hook in vc4 to set the vc4_hdmi_connector_state.output_bpc (and output_format), and will then reuse the value in .atomic_enable() to select whether or not scrambling should be enabled.
However, since our clock rate is pre-computed during .atomic_check(), we end up with the clocks properly configured, but the scrambling disabled, leading to a blank screen.
Let's set mode_changed to true in our HDMI driver to force the update of output_bpc, and thus prevent the issue entirely.
Fixes: ba8c0faebbb0 ("drm/vc4: hdmi: Enable 10/12 bpc output") Signed-off-by: Dom Cobley popcornmix@gmail.com Signed-off-by: Maxime Ripard maxime@cerno.tech --- drivers/gpu/drm/vc4/vc4_hdmi.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index 305807791ebd..03fa2d4c1827 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -1604,9 +1604,14 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder, struct drm_crtc_state *crtc_state, struct drm_connector_state *conn_state) { + struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder); + struct drm_connector *connector = &vc4_hdmi->connector; + struct drm_connector_state *old_conn_state = + drm_atomic_get_old_connector_state(conn_state->state, connector); + struct vc4_hdmi_connector_state *old_vc4_state = + conn_state_to_vc4_hdmi_conn_state(old_conn_state); struct vc4_hdmi_connector_state *vc4_state = conn_state_to_vc4_hdmi_conn_state(conn_state); struct drm_display_mode *mode = &crtc_state->adjusted_mode; - struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder); unsigned long long tmds_char_rate = mode->clock * 1000; unsigned long long tmds_bit_rate; int ret; @@ -1635,6 +1640,11 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder, if (ret) return ret;
+ /* vc4_hdmi_encoder_compute_config may have changed output_bpc and/or output_format */ + if (vc4_state->output_bpc != old_vc4_state->output_bpc || + vc4_state->output_format != old_vc4_state->output_format) + crtc_state->mode_changed = true; + return 0; }