From: Helen Koike <helen.koike@collabora.com>
To: Rob Clark <robdclark@gmail.com>
Cc: "Sean Paul" <sean@poorly.run>,
"Stéphane Marchesin" <marcheu@google.com>,
"Sean Paul" <seanpaul@google.com>,
"David Airlie" <airlied@linux.ie>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
"Tomasz Figa" <tfiga@chromium.org>,
freedreno <freedreno@lists.freedesktop.org>,
boris.brezillon@collabora.com,
"Mamta Shukla" <mamtashukla555@gmail.com>,
stable <stable@vger.kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
kernel@collabora.com, nicholas.kazlauskas@amd.com
Subject: Re: [PATCH v3 3/5] drm/msm: fix fb references in async update
Date: Wed, 3 Apr 2019 15:03:53 -0300 [thread overview]
Message-ID: <7254be23-def1-ed04-7f87-c029e8c40172@collabora.com> (raw)
In-Reply-To: <CAF6AEGtsZ7eoErhnq08kKv3d0NTEG-GKH52ucgvRPNOHkPcOjA@mail.gmail.com>
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
>>
>
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next prev parent reply other threads:[~2019-04-03 18:03 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-14 0:20 [PATCH v3 0/5] drm: Fix fb changes for async updates Helen Koike
2019-03-14 0:20 ` [PATCH v3 3/5] drm/msm: fix fb references in async update Helen Koike
2019-03-27 14:52 ` Rob Clark
2019-04-03 18:03 ` Helen Koike [this message]
2019-05-31 17:54 ` Helen Koike
2019-05-31 18:50 ` Rob Clark
[not found] ` <20190314002027.7833-1-helen.koike-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>
2019-03-14 0:20 ` [PATCH v3 5/5] drm: don't block fb changes for async plane updates Helen Koike
2019-05-07 20:18 ` Sean Paul
2019-05-07 20:18 ` Sean Paul
2019-06-03 16:53 ` Helen Koike
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