Re: [PATCH v6] drm/mediatek: add dma buffer control for drm plane disable

[CK Hu (胡俊光)]

Hi, Yongqiang:

On Tue, 2023-11-21 at 14:50 +0800, Yongqiang Niu wrote:
> the DMA buffer is released when still accessed by Mediatek display
> hardware,
> this flow can lead to M4U reporting a translation fault warning
> 
> add dma buffer control flow in mediatek driver:
> get dma buffer when drm plane disable
> put dma buffer when overlay really disable

In drm_atomic_helper_commit(), it call
drm_atomic_helper_wait_for_vblanks(). And I think this would make sure
that setting has been applied to hardware. So you don't need to modify
mtk_plane_atomic_disable(). If there is bug in
drm_atomic_helper_wait_for_vblanks(), fix
drm_atomic_helper_wait_for_vblanks().

Regards,
CK

> 
> Fixes: 41016fe1028e ("drm: Rename plane->state variables in atomic
> update and disable")
> Signed-off-by: Yongqiang Niu <yongqiang.niu@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c  | 25
> ++++++++++++++++++++++++
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c   |  1 +
>  drivers/gpu/drm/mediatek/mtk_drm_plane.c | 12 ++++++++++++
>  drivers/gpu/drm/mediatek/mtk_drm_plane.h |  1 +
>  4 files changed, 39 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index c277b9fae950..188aaa97e5e3 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -4,6 +4,7 @@
>   */
>  
>  #include <linux/clk.h>
> +#include <linux/dma-buf.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/mailbox_controller.h>
>  #include <linux/of.h>
> @@ -283,6 +284,23 @@ struct mtk_ddp_comp
> *mtk_drm_ddp_comp_for_plane(struct drm_crtc *crtc,
>  	return NULL;
>  }
>  
> +static void mtk_drm_dma_buf_put(struct mtk_drm_crtc *mtk_crtc)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < mtk_crtc->layer_nr; i++) {
> +		struct drm_plane *plane = &mtk_crtc->planes[i];
> +		struct mtk_plane_state *plane_state;
> +
> +		plane_state = to_mtk_plane_state(plane->state);
> +
> +		if (plane_state && plane_state->pending.dma_buf) {
> +			dma_buf_put(plane_state->pending.dma_buf);
> +			plane_state->pending.dma_buf = NULL;
> +		}
> +	}
> +}
> +
>  #if IS_REACHABLE(CONFIG_MTK_CMDQ)
>  static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>  {
> @@ -323,6 +341,8 @@ static void ddp_cmdq_cb(struct mbox_client *cl,
> void *mssg)
>  		mtk_crtc->pending_async_planes = false;
>  	}
>  
> +	mtk_drm_dma_buf_put(mtk_crtc);
> +
>  	mtk_crtc->cmdq_vblank_cnt = 0;
>  	wake_up(&mtk_crtc->cb_blocking_queue);
>  }
> @@ -627,9 +647,14 @@ static void mtk_crtc_ddp_irq(void *data)
>  	else if (mtk_crtc->cmdq_vblank_cnt > 0 && --mtk_crtc-
> >cmdq_vblank_cnt == 0)
>  		DRM_ERROR("mtk_crtc %d CMDQ execute command
> timeout!\n",
>  			  drm_crtc_index(&mtk_crtc->base));
> +
> +	if (!mtk_crtc->cmdq_client.chan)
> +		mtk_drm_dma_buf_put(mtk_crtc);
>  #else
>  	if (!priv->data->shadow_register)
>  		mtk_crtc_ddp_config(crtc, NULL);
> +
> +	mtk_drm_dma_buf_put(mtk_crtc);
>  #endif
>  	mtk_drm_finish_page_flip(mtk_crtc);
>  }
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 2dfaa613276a..4fd232644383 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -1019,4 +1019,5 @@ module_exit(mtk_drm_exit);
>  
>  MODULE_AUTHOR("YT SHEN <yt.shen@xxxxxxxxxxxx>");
>  MODULE_DESCRIPTION("Mediatek SoC DRM driver");
> +MODULE_IMPORT_NS(DMA_BUF);
>  MODULE_LICENSE("GPL v2");
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> index ddc9355b06d5..fbfcd0d1a56c 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> @@ -12,6 +12,7 @@
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_gem_atomic_helper.h>
>  #include <linux/align.h>
> +#include <linux/dma-buf.h>
>  
>  #include "mtk_drm_crtc.h"
>  #include "mtk_drm_ddp_comp.h"
> @@ -283,6 +284,17 @@ static void mtk_plane_atomic_disable(struct
> drm_plane *plane,
>  	struct drm_plane_state *new_state =
> drm_atomic_get_new_plane_state(state,
>  									
>    plane);
>  	struct mtk_plane_state *mtk_plane_state =
> to_mtk_plane_state(new_state);
> +	struct drm_plane_state *old_state =
> drm_atomic_get_old_plane_state(state,
> +									
>    plane);
> +
> +	if (old_state && old_state->fb) {
> +		struct drm_gem_object *gem = old_state->fb->obj[0];
> +
> +		if (gem && gem->dma_buf) {
> +			get_dma_buf(gem->dma_buf);
> +			mtk_plane_state->pending.dma_buf = gem-
> >dma_buf;
> +		}
> +	}
>  	mtk_plane_state->pending.enable = false;
>  	wmb(); /* Make sure the above parameter is set before update */
>  	mtk_plane_state->pending.dirty = true;
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> b/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> index 99aff7da0831..3aba0b58ef3c 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> @@ -33,6 +33,7 @@ struct mtk_plane_pending_state {
>  	bool				async_dirty;
>  	bool				async_config;
>  	enum drm_color_encoding		color_encoding;
> +	struct dma_buf			*dma_buf;
>  };
>  
>  struct mtk_plane_state {