Hi Maxime,
On Tue, 14 Jan 2025 13:54:56 +0100
Herve Codina <herve.codina@xxxxxxxxxxx> wrote:
> Hi Maxime,
>
> On Tue, 14 Jan 2025 08:40:51 +0100
> Maxime Ripard <mripard@xxxxxxxxxx> wrote:
>
> ...
>
> > >
> > > +static int sn65dsi83_reset_pipe(struct sn65dsi83 *sn65dsi83)
> > > +{
> > > + struct drm_atomic_state *state = ERR_PTR(-EINVAL);
> > > + struct drm_device *dev = sn65dsi83->bridge.dev;
> > > + struct drm_connector_state *connector_state;
> > > + struct drm_modeset_acquire_ctx ctx;
> > > + struct drm_connector *connector;
> > > + int err;
> > > +
> > > + /*
> > > + * Reset active outputs of the related CRTC.
> > > + *
> > > + * This way, drm core will reconfigure each components in the CRTC
> > > + * outputs path. In our case, this will force the previous component to
> > > + * go back in LP11 mode and so allow the reconfiguration of SN64DSI83
> > > + * bridge.
> > > + *
> > > + * Keep the lock during the whole operation to be atomic.
> > > + */
> > > +
> > > + DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, err);
> > > +
> > > + state = drm_atomic_helper_duplicate_state(dev, &ctx);
> > > + if (IS_ERR(state)) {
> > > + err = PTR_ERR(state);
> > > + goto unlock;
> > > + }
> >
> > No, you must not allocate a new state for this, you need to reuse the
> > existing state. You'll find it in bridge->base.state->state.
>
> Thanks for pointing that. I didn't know about bridge->base.state->state.
>
> I will use that if using the state is still relevant (see next comment).
>
> >
> > > + state->acquire_ctx = &ctx;
> > > +
> > > + connector = drm_atomic_get_old_connector_for_encoder(state,
> > > + sn65dsi83->bridge.encoder);
> > > + if (!connector) {
> > > + err = -EINVAL;
> > > + goto unlock;
> > > + }
> > > +
> > > + connector_state = drm_atomic_get_connector_state(state, connector);
> > > + if (IS_ERR(connector_state)) {
> > > + err = PTR_ERR(connector_state);
> > > + goto unlock;
> > > + }
> > > +
> > > + err = drm_atomic_helper_reset_pipe(connector_state->crtc, &ctx);
> > > + if (err < 0)
> > > + goto unlock;
> >
> > And you'll find the crtc in bridge->encoder->crtc.
>
> I am a bit confused. I looked at the drm_encoder structure [1] and the crtc
> field available in this structure should not be used by atomic drivers. They
> should rely on &drm_connector_state.crtc.
>
> In my case, I have the feeling that I should get the ctrc from the current
> state (i.e. bridge->base.state->state) using the sequence provided in this
> current patch:
> Retrieve the connector with drm_atomic_get_old_connector_for_encoder()
> Retrieve the connector state with drm_atomic_get_connector_state()
>
> but you pointed out the bridge->encoder->crtc field.
>
> Should I use this field or use the &drm_connector_state.crtc with the drm
> connector state retrieved from bridge->base.state->state using the proposed
> sequence?
>
> [1] https://elixir.bootlin.com/linux/v6.13-rc1/source/include/drm/drm_encoder.h#L180
>
I did some test and I cannot use bridge->base.state->state to retrieve the
CRTC from the current state because this last state field is not set in my
case (i.e. NULL pointer).
So, in the next iteration, I will use directly bridge->encoder->crtc to get
the CRTC.
Best regards,
Hervé
