linux-kernel - Re: [PATCH v4 2/5] drm/amd: fix fb references in async update

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Message-ID: <6edde2bb-c760-884c-1b84-1f88a8752699@collabora.com>
Date:   Mon, 3 Jun 2019 17:14:59 -0300
From:   Helen Koike <helen.koike@...labora.com>
To:     dri-devel@...ts.freedesktop.org, nicholas.kazlauskas@....com
Cc:     andrey.grodzovsky@....com, daniel.vetter@...ll.ch,
        linux-kernel@...r.kernel.org, Tomasz Figa <tfiga@...omium.org>,
        boris.brezillon@...labora.com, David Airlie <airlied@...ux.ie>,
        Sean Paul <seanpaul@...gle.com>, kernel@...labora.com,
        harry.wentland@....com,
        Stéphane Marchesin <marcheu@...gle.com>,
        Leo Li <sunpeng.li@....com>,
        David Francis <David.Francis@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        Anthony Koo <Anthony.Koo@....com>,
        amd-gfx@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
        Christian König <christian.koenig@....com>,
        Mario Kleiner <mario.kleiner.de@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v4 2/5] drm/amd: fix fb references in async update



On 6/3/19 1:56 PM, 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().
> 
> Suggested-by: Boris Brezillon <boris.brezillon@...labora.com>
> Signed-off-by: Helen Koike <helen.koike@...labora.com>
> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

Cc: <stable@...r.kernel.org> # v4.20+
Fixes: 674e78acae0d ("drm/amd/display: Add fast path for cursor plane
updates")


> 
> ---
> 
> Changes in v4: None
> Changes in v3: None
> Changes in v2:
> - added reviewed-by tag
> 
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 443b13ec268d..40624b2c630e 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4347,8 +4347,7 @@ static void dm_plane_atomic_async_update(struct drm_plane *plane,
>  	struct drm_plane_state *old_state =
>  		drm_atomic_get_old_plane_state(new_state->state, plane);
>  
> -	if (plane->state->fb != new_state->fb)
> -		drm_atomic_set_fb_for_plane(plane->state, new_state->fb);
> +	swap(plane->state->fb, new_state->fb);
>  
>  	plane->state->src_x = new_state->src_x;
>  	plane->state->src_y = new_state->src_y;
>