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drm/vc4: hdmi: Force modeset when bpc or format changes

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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>
Link: https://lore.kernel.org/r/20220613144800.326124-32-maxime@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
This commit is contained in:
Dom Cobley 2022-06-13 16:47:58 +02:00 committed by Maxime Ripard
parent 0ee5a40152
commit c94cd0620a
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GPG Key ID: E3EF0D6F671851C5
1 changed files with 11 additions and 1 deletions
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12
drivers/gpu/drm/vc4/vc4_hdmi.c
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@ -1605,9 +1605,14 @@ 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;
@ -1636,6 +1641,11 @@ 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;
}