Hi,
Correcting the tag, just for the record, is v5 of the patch.
On 6/10/19 10:36 AM, Helen Koike wrote:
> commit 89a4aac0ab0e6f5eea10d7bf4869dd15c3de2cd4 upstream.
>
> In the case of a normal sync update, the preparation of framebuffers (be
> it calling drm_atomic_helper_prepare_planes() or doing setups with
> drm_framebuffer_get()) are performed in the new_state and the respective
> cleanups are performed in the old_state.
>
> In the case of async updates, the preparation is also done in the
> new_state but the cleanups are done in the new_state (because updates
> are performed in place, i.e. in the current state).
>
> The current code blocks async udpates when the fb is changed, turning
> async updates into sync updates, slowing down cursor updates and
> introducing regressions in igt tests with errors of type:
>
> "CRITICAL: completed 97 cursor updated in a period of 30 flips, we
> expect to complete approximately 15360 updates, with the threshold set
> at 7680"
>
> Fb changes in async updates were prevented to avoid the following scenario:
>
> - Async update, oldfb = NULL, newfb = fb1, prepare fb1, cleanup fb1
> - Async update, oldfb = fb1, newfb = fb2, prepare fb2, cleanup fb2
> - Non-async commit, oldfb = fb2, newfb = fb1, prepare fb1, cleanup fb2 (wrong)
> Where we have a single call to prepare fb2 but double cleanup call to fb2.
>
> To solve the above problems, instead of blocking async fb changes, we
> place the old framebuffer in the new_state object, so when the code
> performs cleanups in the new_state it will cleanup the old_fb and we
> will have the following scenario instead:
>
> - Async update, oldfb = NULL, newfb = fb1, prepare fb1, no cleanup
> - Async update, oldfb = fb1, newfb = fb2, prepare fb2, cleanup fb1
> - Non-async commit, oldfb = fb2, newfb = fb1, prepare fb1, cleanup fb2
>
> Where calls to prepare/cleanup are balanced.
>
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
> Fixes: 25dc194b34dd ("drm: Block fb changes for async plane updates")
> Suggested-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Signed-off-by: Helen Koike <helen.koike@xxxxxxxxxxxxx>
> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Link: https://patchwork.freedesktop.org/patch/msgid/20190603165610.24614-6-helen.koike@xxxxxxxxxxxxx
> ---
>
> Hi,
>
> This patch failed to apply on kernel stable v4.14, I'm re-sending it
> fixing the conflict.
fyi, this patch was already applied in other stable branches.
Thanks
Helen
>
> Thanks
> Helen
>
> drivers/gpu/drm/drm_atomic_helper.c | 10 ++++++++++
> include/drm/drm_modeset_helper_vtables.h | 8 ++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index d05ed0521e20..331478bd2ff8 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1462,6 +1462,8 @@ EXPORT_SYMBOL(drm_atomic_helper_async_check);
> * drm_atomic_async_check() succeeds. Async commits are not supposed to swap
> * the states like normal sync commits, but just do in-place changes on the
> * current state.
> + *
> + * TODO: Implement full swap instead of doing in-place changes.
> */
> void drm_atomic_helper_async_commit(struct drm_device *dev,
> struct drm_atomic_state *state)
> @@ -1472,8 +1474,16 @@ void drm_atomic_helper_async_commit(struct drm_device *dev,
> int i;
>
> for_each_new_plane_in_state(state, plane, plane_state, i) {
> + struct drm_framebuffer *old_fb = plane->state->fb;
> +
> funcs = plane->helper_private;
> funcs->atomic_async_update(plane, plane_state);
> +
> + /*
> + * Make sure the FBs have been swapped so that cleanups in the
> + * new_state performs a cleanup in the old FB.
> + */
> + WARN_ON_ONCE(plane_state->fb != old_fb);
> }
> }
> EXPORT_SYMBOL(drm_atomic_helper_async_commit);
> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> index c55cf3ff6847..2f6d0f3ae985 100644
> --- a/include/drm/drm_modeset_helper_vtables.h
> +++ b/include/drm/drm_modeset_helper_vtables.h
> @@ -1159,6 +1159,14 @@ struct drm_plane_helper_funcs {
> * current one with the new plane configurations in the new
> * plane_state.
> *
> + * Drivers should also swap the framebuffers between current plane
> + * state (&drm_plane.state) and new_state.
> + * This is required since cleanup for async commits is performed on
> + * the new state, rather than old state like for traditional commits.
> + * Since we want to give up the reference on the current (old) fb
> + * instead of our brand new one, swap them in the driver during the
> + * async commit.
> + *
> * FIXME:
> * - It only works for single plane updates
> * - Async Pageflips are not supported yet
>
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