Hi Rob,
On 3/27/19 11:52 AM, Rob Clark wrote:
On Wed, Mar 13, 2019 at 8:21 PM Helen Koike helen.koike@collabora.com wrote:
Async update callbacks are expected to set the old_fb in the new_state so prepare/cleanup framebuffers are balanced.
Cc: stable@vger.kernel.org # v4.14+ Fixes: 224a4c970987 ("drm/msm: update cursors asynchronously through atomic") Suggested-by: Boris Brezillon boris.brezillon@collabora.com Signed-off-by: Helen Koike helen.koike@collabora.com
Hello,
As mentioned in the cover letter, But I couldn't test on MSM because I don't have the hardware and I would appreciate if anyone could test it.
In other platforms (VC4, AMD, Rockchip), there is a hidden drm_framebuffer_get(new_fb)/drm_framebuffer_put(old_fb) in async_update that is wrong, but I couldn't identify those here, not sure if it is hidden somewhere else, but if tests fail this is probably the cause.
Thanks! Helen
Apologies, I haven't had a chance to test this yet, and it is likely to be a few weeks before I have a chance..
That said, not refcnt'ing the fb seems suspicious. I read the explanation in the other patches, but kind of think it is more clear to keep the extra refcnt'ing.. or at least have a comment.
Refcnt'ing is taken care by drm_mode_cursor_universal() when calling drm_atomic_helper_update_plane(). The other codes had a drm_atomic_set_fb_for_plane() (which get a referent of the new fb and put the old fb), but the problem is that the cleanup_plane will also put the ref of the old fb. In the other drivers I saw, drm_atomic_set_fb_for_plane() shouldn't be called, but this issue should be triggered very easily with a test.
I can add this is in the async_check() docs.
I do a bit wonder if we hold the ref to the outgoing cursor long enough.. I think the hw will actually continue to scan it out until the next vblank. But Archit was the one who added async_update support so maybe that is handled somewhere else. It's been a while since I've looked at this.
I don't know much about MSM, but if I understand correctly, MSM don't support true async, is that correct?
Then I think we need to do something similar to the rockchip:
https://patchwork.kernel.org/patch/10852039/
and setup a drm_flip_work_queue(). But this seems another problem that is already there no? Not really related to this patch. I could send a separate patch for this (but I don't have the means to test it).
Regards, Helen
BR, -R
Changes in v3: None Changes in v2:
- update CC stable and Fixes tag
drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c index be13140967b4..b854f471e9e5 100644 --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c @@ -502,6 +502,8 @@ static int mdp5_plane_atomic_async_check(struct drm_plane *plane, static void mdp5_plane_atomic_async_update(struct drm_plane *plane, struct drm_plane_state *new_state) {
struct drm_framebuffer *old_fb = plane->state->fb;plane->state->src_x = new_state->src_x; plane->state->src_y = new_state->src_y; plane->state->crtc_x = new_state->crtc_x;@@ -524,6 +526,8 @@ static void mdp5_plane_atomic_async_update(struct drm_plane *plane,
*to_mdp5_plane_state(plane->state) = *to_mdp5_plane_state(new_state);
new_state->fb = old_fb;}
static const struct drm_plane_helper_funcs mdp5_plane_helper_funcs = {
2.20.1