linux-kernel - Re: [PATCH 2/8] drm/rockchip: Get rid of some unnecessary code

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Date:   Sun, 18 Sep 2016 09:50:38 +0800
From:   Mark yao <mark.yao@...k-chips.com>
To:     Tomasz Figa <tfiga@...omium.org>, dri-devel@...ts.freedesktop.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Heiko Stuebner <heiko@...ech.de>,
        David Airlie <airlied@...ux.ie>,
        Sean Paul <seanpaul@...omium.org>,
        Daniel Kurtz <djkurtz@...omium.org>
Subject: Re: [PATCH 2/8] drm/rockchip: Get rid of some unnecessary code

On 2016年09月14日 20:54, Tomasz Figa wrote:
> Current code implements prepare_fb and cleanup_fb callbacks only to
> grab/release fb references, which is already done by atomic framework
> when creating/destryoing plane state. Let's remove these
> unused bits.
>
> Signed-off-by: Tomasz Figa <tfiga@...omium.org>
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 18 ------------------
>   1 file changed, 18 deletions(-)

Hi Tomasz

I think we can't get rid of the prepare_fb and cleanup_fb

see the reason:
commit 44d0237a26395ac94160cf23f32769013b365590
Author: Mark Yao <mark.yao@...k-chips.com>
Date:   Fri Apr 29 11:37:20 2016 +0800

     drm/rockchip: vop: fix iommu crash with async atomic

     After async atomic_commit callback, drm_atomic_clean_old_fb will
     clean all old fb, but because async, the old fb may be also on
     the vop hardware, dma will access the old fb buffer, clean old
     fb will cause iommu page fault.

     Reference the fb and unreference it when the fb actuall swap out
     from vop hardware.


> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 7e811cf..68988c6 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -641,22 +641,6 @@ static void vop_plane_destroy(struct drm_plane *plane)
>   	drm_plane_cleanup(plane);
>   }
>   
> -static int vop_plane_prepare_fb(struct drm_plane *plane,
> -				struct drm_plane_state *new_state)
> -{
> -	if (plane->state->fb)
> -		drm_framebuffer_reference(plane->state->fb);
> -
> -	return 0;
> -}
> -
> -static void vop_plane_cleanup_fb(struct drm_plane *plane,
> -				 struct drm_plane_state *old_state)
> -{
> -	if (old_state->fb)
> -		drm_framebuffer_unreference(old_state->fb);
> -}
> -
>   static int vop_plane_atomic_check(struct drm_plane *plane,
>   			   struct drm_plane_state *state)
>   {
> @@ -849,8 +833,6 @@ static void vop_plane_atomic_update(struct drm_plane *plane,
>   }
>   
>   static const struct drm_plane_helper_funcs plane_helper_funcs = {
> -	.prepare_fb = vop_plane_prepare_fb,
> -	.cleanup_fb = vop_plane_cleanup_fb,
>   	.atomic_check = vop_plane_atomic_check,
>   	.atomic_update = vop_plane_atomic_update,
>   	.atomic_disable = vop_plane_atomic_disable,


-- 
Ｍark Yao