Re: [PATCH 5/5] drm/vc4: fix fb references in async update

[Helen Koike]

On 3/4/19 11:49 AM, Helen Koike wrote:
> Async update callbacks are expected to set the old_fb in the new_state
> so prepare/cleanup framebuffers are balanced.
> 
> Calling drm_atomic_set_fb_for_plane() (which gets a reference of the new
> fb and put the old fb) is not required, as it's taken care by
> drm_mode_cursor_universal() when calling drm_atomic_helper_update_plane().
> 
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.19+: 25dc194b34dd: drm: Block fb changes for async plane updates
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.19+: 8105bbaf9afd: drm: don't block fb changes for async plane updates
> 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>
> 
> ---
> Hello,
> 
> As mentioned in the cover letter,
> I tested on the rockchip and on i915 using igt plane_cursor_legacy and
> kms_cursor_legacy and I didn't see any regressions.
> But I couldn't test on VC4. I have a Raspberry pi model B rev2, when
> FB_SIMPLE is running I can see output on the screen, but when vc4 is
> loaded my hdmi display is not detected anymore, I am still debugging
> this, probably some config in the firmware, but I would appreciate if
> anyone could help me testing it.

I managed to test on VC4, and the difference between the test results
with and without the patch is:

- cursor-vs-flip-toggle -> this test was getting a timeout and now is
failing due to:
completed 64 cursor updated in a period of 30 flips, we expect to
complete approximately 480 updates, with the threshold set at 240
Subtest cursor-vs-flip-toggle failed.
- flip-vs-cursor-toggle -> this was getting a timeout and now is passing
- short-flip-after-cursor-toggle -> this was failing and now is passing
- short-flip-before-cursor-toggle -> this was failing and now is passing

You can check the tests results before the patch series [1] and after
[2] in the links below:

[1] https://people.collabora.com/~koike/vc4-results-5.0.0-rc7+vanila/html/
[2] https://people.collabora.com/~koike/vc4-results-5.0.0-rc7+fb-patch/html/

I would appreciate is someone could review this patch.

Thanks!
Helen

> 
> Also the Cc statble commit hash dependency needs to be updated once the
> refered commit is merged.
> 
> Thanks!
> Helen
> 
>  drivers/gpu/drm/vc4/vc4_plane.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
> index 1babfeca0c92..1235e53b22a3 100644
> --- a/drivers/gpu/drm/vc4/vc4_plane.c
> +++ b/drivers/gpu/drm/vc4/vc4_plane.c
> @@ -968,7 +968,7 @@ static void vc4_plane_atomic_async_update(struct drm_plane *plane,
>  {
>  	struct vc4_plane_state *vc4_state, *new_vc4_state;
>  
> -	drm_atomic_set_fb_for_plane(plane->state, state->fb);
> +	swap(plane->state->fb, state->fb);
>  	plane->state->crtc_x = state->crtc_x;
>  	plane->state->crtc_y = state->crtc_y;
>  	plane->state->crtc_w = state->crtc_w;
>