Re: [PATCH 2/2 v2] drm/atomic: clear new_state pointers at hw_done

[Enric Balletbo Serra <eballetbo@gmail.com>]

Hi Rob,

Missatge de Rob Clark <robdclark@gmail.com> del dia dl., 4 de nov.
2019 a les 18:42:
>
> From: Rob Clark <robdclark@chromium.org>
>
> The new state should not be accessed after this point.  Clear the
> pointers to make that explicit.
>
> Signed-off-by: Rob Clark <robdclark@chromium.org>

While looking to another issue I applied this patch on top of 5.4-rc7
and my display stopped working. The system gets stuck with the
messages below

...
[   17.558689] rockchip-vop ff8f0000.vop: Adding to iommu group 1
[   17.566014] rk3399-gru-sound sound: ASoC: failed to init link DP: -517
[   17.567618] rockchip-vop ff900000.vop: Adding to iommu group 2
[   17.580671] rk3399-gru-sound sound: ASoC: failed to init link DP: -517
[   17.585996] rockchip-drm display-subsystem: bound ff8f0000.vop (ops
vop_component_ops [rockchipdrm])
[   17.589294] rk3399-gru-sound sound: ASoC: failed to init link DP: -517
[   17.599899] rockchip-drm display-subsystem: bound ff900000.vop (ops
vop_component_ops [rockchipdrm])
[   17.615846] rockchip-dp ff970000.edp: no DP phy configured
[   17.622495] rockchip-drm display-subsystem: bound ff970000.edp (ops
rockchip_dp_component_ops [rockchipdrm])
[   17.633688] rockchip-drm display-subsystem: bound fec00000.dp (ops
cdn_dp_component_ops [rockchipdrm])
[   17.644141] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[   17.651548] [drm] No driver support for vblank timestamp query.

Not really useful information at this point, but I am wondering if
could be that the rockchip driver is doing something wrong more than
this patch is wrong?

Thanks,
 Enric

> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 30 +++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 648494c813e5..aec9759d9df2 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2246,12 +2246,42 @@ EXPORT_SYMBOL(drm_atomic_helper_fake_vblank);
>   */
>  void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
>  {
> +       struct drm_connector *connector;
> +       struct drm_connector_state *old_conn_state, *new_conn_state;
>         struct drm_crtc *crtc;
>         struct drm_crtc_state *old_crtc_state, *new_crtc_state;
> +       struct drm_plane *plane;
> +       struct drm_plane_state *old_plane_state, *new_plane_state;
>         struct drm_crtc_commit *commit;
> +       struct drm_private_obj *obj;
> +       struct drm_private_state *old_obj_state, *new_obj_state;
>         int i;
>
> +       /*
> +        * After this point, drivers should not access the permanent modeset
> +        * state, so we also clear the new_state pointers to make this
> +        * restriction explicit.
> +        *
> +        * For the CRTC state, we do this in the same loop where we signal
> +        * hw_done, since we still need to new_crtc_state to fish out the
> +        * commit.
> +        */
> +
> +       for_each_oldnew_connector_in_state(old_state, connector, old_conn_state, new_conn_state, i) {
> +               old_state->connectors[i].new_state = NULL;
> +       }
> +
> +       for_each_oldnew_plane_in_state(old_state, plane, old_plane_state, new_plane_state, i) {
> +               old_state->planes[i].new_state = NULL;
> +       }
> +
> +       for_each_oldnew_private_obj_in_state(old_state, obj, old_obj_state, new_obj_state, i) {
> +               old_state->private_objs[i].new_state = NULL;
> +       }
> +
>         for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
> +               old_state->crtcs[i].new_state = NULL;
> +
>                 commit = new_crtc_state->commit;
>                 if (!commit)
>                         continue;
> --
> 2.23.0
>
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