[PATCH 2/2] drm: rcar-du: Don't restart group when enabling plane on Gen3

[Kieran Bingham]

Quoting Laurent Pinchart (2022-02-21 17:13:40)
> On Gen3 hardware enabling a VSP plane doesn't change any register that
> requires DRES to take effect. Avoid a group restart in that case.

This also makes it clear that the need_restart is due to the change
occuring in the VSP1 sink, so I think this is cleaner all round.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>

> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> ---
>  drivers/gpu/drm/rcar-du/rcar_du_plane.c | 6 ++++++
>  drivers/gpu/drm/rcar-du/rcar_du_vsp.c   | 9 ---------
>  2 files changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
> index 9b058d6cb032..22aeeb1cc1fb 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
> @@ -560,6 +560,12 @@ void __rcar_du_plane_setup(struct rcar_du_group *rgrp,
>                 if (rcdu->vspd1_sink != vspd1_sink) {
>                         rcdu->vspd1_sink = vspd1_sink;
>                         rcar_du_set_dpad0_vsp1_routing(rcdu);
> +
> +                       /*
> +                        * Changes to the VSP1 sink take effect on DRES and thus
> +                        * need a restart of the group.
> +                        */
> +                       rgrp->need_restart = true;
>                 }
>         }
>  }
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> index b7fc5b069cbc..32530d698e75 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
> @@ -84,15 +84,6 @@ void rcar_du_vsp_enable(struct rcar_du_crtc *crtc)
>  
>         __rcar_du_plane_setup(crtc->group, &state);
>  
> -       /*
> -        * Ensure that the plane source configuration takes effect by requesting
> -        * a restart of the group. See rcar_du_plane_atomic_update() for a more
> -        * detailed explanation.
> -        *
> -        * TODO: Check whether this is still needed on Gen3.
> -        */
> -       crtc->group->need_restart = true;
> -
>         vsp1_du_setup_lif(crtc->vsp->vsp, crtc->vsp_pipe, &cfg);
>  }
>  
> -- 
> Regards,
> 
> Laurent Pinchart
>