On Thu, May 30, 2024 at 03:06:20PM +0530, Aradhya Bhatia wrote:
> Move the bridge pre_enable call before crtc enable, and the bridge
> post_disable call after the crtc disable.
>
> The sequence of enable after this patch will look like:
>
> bridge[n]_pre_enable
> ...
> bridge[1]_pre_enable
>
> crtc_enable
> encoder_enable
>
> bridge[1]_enable
> ...
> bridge[n]__enable
>
> and vice-versa for the bridge chain disable sequence.
>
> The definition of bridge pre_enable hook says that,
> "The display pipe (i.e. clocks and timing signals) feeding this bridge
> will not yet be running when this callback is called".
>
> Since CRTC is also a source feeding the bridge, it should not be enabled
> before the bridges in the pipeline are pre_enabled. Fix that by
> re-ordering the sequence of bridge pre_enable and bridge post_disable.
>
> Signed-off-by: Aradhya Bhatia <a-bhatia1@xxxxxx>
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 70 +++++++++++++++++++++++++++--
> 1 file changed, 67 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index fb97b51b38f1..02e093950218 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1186,8 +1186,6 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
> else if (funcs->dpms)
> funcs->dpms(encoder, DRM_MODE_DPMS_OFF);
> }
> -
> - drm_atomic_bridge_chain_post_disable(bridge, old_state);
> }
>
> for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
> @@ -1234,6 +1232,49 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
> if (ret == 0)
> drm_crtc_vblank_put(crtc);
> }
> +
> + for_each_oldnew_connector_in_state(old_state, connector, old_conn_state,
> + new_conn_state, i) {
> + struct drm_encoder *encoder;
> + struct drm_bridge *bridge;
> +
> + /*
> + * Shut down everything that's in the changeset and currently
> + * still on. So need to check the old, saved state.
> + */
> + if (!old_conn_state->crtc)
> + continue;
> +
> + old_crtc_state = drm_atomic_get_old_crtc_state(old_state, old_conn_state->crtc);
> +
> + if (new_conn_state->crtc)
> + new_crtc_state = drm_atomic_get_new_crtc_state(old_state,
> + new_conn_state->crtc);
> + else
> + new_crtc_state = NULL;
> +
> + if (!crtc_needs_disable(old_crtc_state, new_crtc_state) ||
> + !drm_atomic_crtc_needs_modeset(old_conn_state->crtc->state))
> + continue;
> +
> + encoder = old_conn_state->best_encoder;
> +
> + /* We shouldn't get this far if we didn't previously have
> + * an encoder.. but WARN_ON() rather than explode.
> + */
> + if (WARN_ON(!encoder))
> + continue;
> +
> + drm_dbg_atomic(dev, "disabling [ENCODER:%d:%s]\n",
> + encoder->base.id, encoder->name);
This duplicates the code in the loop around
drm_atomic_bridge_chain_disable(). Can it be extracted to a separate
function? Code duplication is nearly always a bad idea.
The same comment applies to the next chunk too.
> +
> + /*
> + * Each encoder has at most one connector (since we always steal
> + * it away), so we won't call disable hooks twice.
> + */
> + bridge = drm_bridge_chain_get_first_bridge(encoder);
> + drm_atomic_bridge_chain_post_disable(bridge, old_state);
> + }
> }
>
> /**
--
With best wishes
Dmitry
