Re: [PATCH v3 3/5] drm/msm: fix fb references in async update

[Helen Koike <helen@koikeco.de>]

Hello,

On 3/13/19 9:20 PM, Helen Koike 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.

I got this tested on a dragonboard 410c, no regressions where found and
no extra warnings.

These two tests where already failing for other reasons:
flip-vs-cursor-crc-atomic
flip-vs-cursor-crc-legacy

If you want to see the full log:

https://people.collabora.com/~koike/drm-fixes-results.zip

Thanks
Helen

> 
> 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
> 
> 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 = {
>