On Wed, Apr 23, 2014 at 05:37:30PM +0200, Daniel Vetter wrote:
> The introduction of primary planes has apparently caused a bit of fb
> refcounting fun for people. That makes it a good time to clean up the
> arcane rules and slight differences between ->update_plane and
> ->set_config. The new rules are:
>
> - The core holds a reference for both the new and the old fb (if
> they're non-NULL of course) while calling into the driver through
> either ->update_plane or ->set_config.
>
> - Drivers may not clobber plane->fb if their callback fails. If they
> do that, they need to store a pointer to the old fb in it again.
> When calling into the driver plane->fb still points at the current
> (old) framebuffer.
>
> - The core will update the plane->fb pointer on success. Drivers can
> do that themselves too, but aren't required to any more for the
> primary plane.
>
> - The core will update fb refcounts for the plane->fb pointer,
> presuming the drivers hold up their end of the bargain.
>
> v2: Remove now unused tmpfb (Thierry)
>
> v3: Drop broken changes from drm_mode_setplane (Ville). Also polish
> the commit message a bit.
>
> v4: Also fix up the handling of ->disable_plane in
> drm_plane_force_disable. The issue was that we didn't save plane->fb
> over the ->disable_plane call. Just paranoia, nothing relies on this.
>
> v5: Keep still useful comments about directly calling ->set_config,
> which I should have done for v4 already. Requested by Matt.
>
> Cc: Thierry Reding <treding@xxxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_crtc.c | 13 +++++++------
> drivers/gpu/drm/drm_plane_helper.c | 10 +---------
> 2 files changed, 8 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index d8b7099abece..f6633cb927bc 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -1145,16 +1145,17 @@ EXPORT_SYMBOL(drm_plane_cleanup);
> */
> void drm_plane_force_disable(struct drm_plane *plane)
> {
> + struct drm_framebuffer *old_fb = plane->fb;
> int ret;
>
> - if (!plane->fb)
> + if (!old_fb)
> return;
>
> ret = plane->funcs->disable_plane(plane);
> if (ret)
> DRM_ERROR("failed to disable plane with busy fb\n");
> /* disconnect the plane from the fb and crtc: */
> - __drm_framebuffer_unreference(plane->fb);
> + __drm_framebuffer_unreference(old_fb);
> plane->fb = NULL;
> plane->crtc = NULL;
> }
> @@ -2187,16 +2188,18 @@ int drm_mode_setplane(struct drm_device *dev, void *data,
> }
>
> drm_modeset_lock_all(dev);
> + old_fb = plane->fb;
> ret = plane->funcs->update_plane(plane, crtc, fb,
> plane_req->crtc_x, plane_req->crtc_y,
> plane_req->crtc_w, plane_req->crtc_h,
> plane_req->src_x, plane_req->src_y,
> plane_req->src_w, plane_req->src_h);
> if (!ret) {
> - old_fb = plane->fb;
> plane->crtc = crtc;
> plane->fb = fb;
> fb = NULL;
> + } else {
> + old_fb = NULL;
> }
> drm_modeset_unlock_all(dev);
>
> @@ -2239,9 +2242,7 @@ int drm_mode_set_config_internal(struct drm_mode_set *set)
> ret = crtc->funcs->set_config(set);
> if (ret == 0) {
> crtc->primary->crtc = crtc;
> -
> - /* crtc->fb must be updated by ->set_config, enforces this. */
> - WARN_ON(fb != crtc->primary->fb);
> + crtc->primary->fb = fb;
> }
>
> list_for_each_entry(tmp, &crtc->dev->mode_config.crtc_list, head) {
> diff --git a/drivers/gpu/drm/drm_plane_helper.c b/drivers/gpu/drm/drm_plane_helper.c
> index 9540ff9f97fe..d966afa7ecae 100644
> --- a/drivers/gpu/drm/drm_plane_helper.c
> +++ b/drivers/gpu/drm/drm_plane_helper.c
> @@ -124,7 +124,6 @@ int drm_primary_helper_update(struct drm_plane *plane, struct drm_crtc *crtc,
> .y2 = crtc->mode.vdisplay,
> };
> struct drm_connector **connector_list;
> - struct drm_framebuffer *tmpfb;
> int num_connectors, ret;
>
> if (!crtc->enabled) {
> @@ -178,21 +177,14 @@ int drm_primary_helper_update(struct drm_plane *plane, struct drm_crtc *crtc,
> set.num_connectors = num_connectors;
>
> /*
> - * set_config() adjusts crtc->primary->fb; however the DRM setplane
> - * code that called us expects to handle the framebuffer update and
> - * reference counting; save and restore the current fb before
> - * calling it.
> - *
> - * N.B., we call set_config() directly here rather than using
> + * We call set_config() directly here rather than using
> * drm_mode_set_config_internal. We're reprogramming the same
> * connectors that were already in use, so we shouldn't need the extra
> * cross-CRTC fb refcounting to accomodate stealing connectors.
> * drm_mode_setplane() already handles the basic refcounting for the
> * framebuffers involved in this operation.
> */
> - tmpfb = plane->fb;
> ret = crtc->funcs->set_config(&set);
> - plane->fb = tmpfb;
>
> kfree(connector_list);
> return ret;
> --
> 1.9.2
>
--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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