Hi Peter,

Thank you for the patch and sorry for the late review.

On Friday, 5 January 2018 13:30:37 EET Peter Ujfalusi wrote:
> Use the plane index as default zpos for all planes. Even if the
> application is not setting zpos/zorder explicitly we will have unique zpos
> for each plane.
> 
> Enforce that all planes must have unique zpos on the given crtc.

Could you explain the rationale for that in the commit message, what's wrong 
with duplicate zpos values ?

Isn't there a risk of breaking the non-atomic userspace with this ? Without 
atomic commits userspace can't change the zpos of multiple planes in one go, 
so it might be impossible to reorder planes without going through a state that 
has duplicated zpos values.

> Signed-off-by: Peter Ujfalusi <peter.ujfal...@ti.com>
> ---
> Hi,
> 
> Changes since v3:
> - Use drm_plane_index() instead of storing the same index wothin omap_plane
>   struct
> - Optimize the zpos validation loop so we avoid extra checks.
> 
> Changes since v2:
> - The check for duplicate zpos is moved to omap_crtc
> 
> Changes since v1:
> - Dropped the zpos normalization related patches
> - New patch based on the discussion, see commit message.
> 
> Regards,
> Peter
> 
>  drivers/gpu/drm/omapdrm/omap_crtc.c  | 36 ++++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/omapdrm/omap_plane.c | 15 ++++-----------
>  2 files changed, 39 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c
> b/drivers/gpu/drm/omapdrm/omap_crtc.c index cc85c16cbc2a..c68e3a4f5b7d
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_crtc.c
> +++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
> @@ -452,6 +452,40 @@ static void omap_crtc_mode_set_nofb(struct drm_crtc
> *crtc) }
>  }
> 
> +static int omap_crtc_validate_zpos(struct drm_crtc *crtc,
> +                                struct drm_crtc_state *state)
> +{
> +     struct drm_device *ddev = crtc->dev;
> +     struct drm_plane *p1;
> +     const struct drm_plane_state *pstate1;
> +
> +     /* Check the crts's planes against duplicated zpos value */
> +     drm_atomic_crtc_state_for_each_plane_state(p1, pstate1, state) {
> +             struct drm_plane *p2 = p1;
> +
> +             list_for_each_entry_continue(p2, &ddev->mode_config.plane_list,
> +                                          head) {
> +                     const struct drm_plane_state *pstate2;
> +
> +                     if (!(state->plane_mask & (1 << drm_plane_index(p2))))
> +                             continue;
> +
> +                     pstate2 = __drm_atomic_get_current_plane_state(
> +                                                     state->state, p2);
> +                     if (!pstate2)
> +                             continue;
> +
> +                     if (pstate1->zpos == pstate2->zpos) {
> +                             DBG("crtc%u: zpos must be unique (zpos: %u)",
> +                             crtc->index, pstate1->zpos);
> +                             return -EINVAL;
> +                     }
> +             }
> +     }

That seems a bit complicated to me. Couldn't we use a single loop and a zpos 
bitfield ? Something like the following (untested) code.

        struct drm_device *ddev = crtc->dev;
        const struct drm_plane_state *plane_state;
        struct drm_plane *plane;
        unsigned int zpos_mask = 0;

        /* Check the crts's planes against duplicated zpos value */
        drm_atomic_crtc_state_for_each_plane_state(plane, plane_state, state) {
                if (zpos_mask & BIT(plane_state->zpos)) {
                        DBG("crtc%u: zpos must be unique (zpos: %u)",
                            crtc->index, plane_state->zpos);
                        return -EINVAL;
                }

                zpos_mask |= BIT(plane_state->zpos); 
        }

        return 0;

> +     return 0;
> +}
> +
>  static int omap_crtc_atomic_check(struct drm_crtc *crtc,
>                               struct drm_crtc_state *state)
>  {
> @@ -475,7 +509,7 @@ static int omap_crtc_atomic_check(struct drm_crtc *crtc,
> omap_crtc_state->rotation = pri_state->rotation;
>       }
> 
> -     return 0;
> +     return omap_crtc_validate_zpos(crtc, state);
>  }
> 
>  static void omap_crtc_atomic_begin(struct drm_crtc *crtc,
> diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c
> b/drivers/gpu/drm/omapdrm/omap_plane.c index 15e5d5d325c6..d0057a23a5ac
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_plane.c
> +++ b/drivers/gpu/drm/omapdrm/omap_plane.c
> @@ -99,8 +99,7 @@ static void omap_plane_atomic_disable(struct drm_plane
> *plane, struct omap_plane *omap_plane = to_omap_plane(plane);
> 
>       plane->state->rotation = DRM_MODE_ROTATE_0;
> -     plane->state->zpos = plane->type == DRM_PLANE_TYPE_PRIMARY
> -                        ? 0 : omap_plane->id;
> +     plane->state->zpos = drm_plane_index(plane);
> 
>       priv->dispc_ops->ovl_enable(omap_plane->id, false);
>  }
> @@ -186,18 +185,12 @@ void omap_plane_install_properties(struct drm_plane
> *plane,
> 
>  static void omap_plane_reset(struct drm_plane *plane)
>  {
> -     struct omap_plane *omap_plane = to_omap_plane(plane);
> -
>       drm_atomic_helper_plane_reset(plane);
>       if (!plane->state)
>               return;
> 
> -     /*
> -      * Set the zpos default depending on whether we are a primary or overlay
> -      * plane.
> -      */
> -     plane->state->zpos = plane->type == DRM_PLANE_TYPE_PRIMARY
> -                        ? 0 : omap_plane->id;
> +     /* Set the zpos to the plane index. */
> +     plane->state->zpos = drm_plane_index(plane);
>  }
> 
>  static int omap_plane_atomic_set_property(struct drm_plane *plane,
> @@ -297,7 +290,7 @@ struct drm_plane *omap_plane_init(struct drm_device
> *dev, drm_plane_helper_add(plane, &omap_plane_helper_funcs);
> 
>       omap_plane_install_properties(plane, &plane->base);
> -     drm_plane_create_zpos_property(plane, 0, 0, num_planes - 1);
> +     drm_plane_create_zpos_property(plane, idx, 0, num_planes - 1);
> 
>       return plane;

-- 
Regards,

Laurent Pinchart

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