linux-kernel - Re: [PATCH] drm/virtio: drop quirks handling

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Date:   Tue, 8 Sep 2020 10:57:21 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/virtio: drop quirks handling

On Tue, Sep 08, 2020 at 08:47:41AM +0200, Gerd Hoffmann wrote:
> These days dma ops can be overridden per device, and the virtio core

"can be overridden" or "are"? The comment above vring_use_dma_api()
suggests that's not yet done. If that's wrong then I think updating the
comment would be really good.
-Daniel

> uses that to handle the dma quirks transparently for the rest of the
> kernel.  So we can drop the virtio_has_dma_quirk() checks, just use
> the dma api unconditionally and depend on the virtio core having setup
> dma_ops as needed.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_object.c | 19 ++++++-------------
>  drivers/gpu/drm/virtio/virtgpu_vq.c     | 16 ++++++----------
>  2 files changed, 12 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
> index 729f98ad7c02..9c35ce64ff9e 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_object.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_object.c
> @@ -141,7 +141,6 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
>  					struct virtio_gpu_mem_entry **ents,
>  					unsigned int *nents)
>  {
> -	bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);
>  	struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo);
>  	struct scatterlist *sg;
>  	int si, ret;
> @@ -162,15 +161,11 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
>  		return -EINVAL;
>  	}
>  
> -	if (use_dma_api) {
> -		shmem->mapped = dma_map_sg(vgdev->vdev->dev.parent,
> -					   shmem->pages->sgl,
> -					   shmem->pages->nents,
> -					   DMA_TO_DEVICE);
> -		*nents = shmem->mapped;
> -	} else {
> -		*nents = shmem->pages->nents;
> -	}
> +	shmem->mapped = dma_map_sg(vgdev->vdev->dev.parent,
> +				   shmem->pages->sgl,
> +				   shmem->pages->nents,
> +				   DMA_TO_DEVICE);
> +	*nents = shmem->mapped;
>  
>  	*ents = kmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),
>  			      GFP_KERNEL);
> @@ -180,9 +175,7 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
>  	}
>  
>  	for_each_sg(shmem->pages->sgl, sg, *nents, si) {
> -		(*ents)[si].addr = cpu_to_le64(use_dma_api
> -					       ? sg_dma_address(sg)
> -					       : sg_phys(sg));
> +		(*ents)[si].addr = cpu_to_le64(sg_dma_address(sg));
>  		(*ents)[si].length = cpu_to_le32(sg->length);
>  		(*ents)[si].padding = 0;
>  	}
> diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
> index c93c2db35aaf..1c1d2834547d 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_vq.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
> @@ -599,13 +599,11 @@ void virtio_gpu_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev,
>  	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(objs->objs[0]);
>  	struct virtio_gpu_transfer_to_host_2d *cmd_p;
>  	struct virtio_gpu_vbuffer *vbuf;
> -	bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);
>  	struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo);
>  
> -	if (use_dma_api)
> -		dma_sync_sg_for_device(vgdev->vdev->dev.parent,
> -				       shmem->pages->sgl, shmem->pages->nents,
> -				       DMA_TO_DEVICE);
> +	dma_sync_sg_for_device(vgdev->vdev->dev.parent,
> +			       shmem->pages->sgl, shmem->pages->nents,
> +			       DMA_TO_DEVICE);
>  
>  	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
>  	memset(cmd_p, 0, sizeof(*cmd_p));
> @@ -1015,13 +1013,11 @@ void virtio_gpu_cmd_transfer_to_host_3d(struct virtio_gpu_device *vgdev,
>  	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(objs->objs[0]);
>  	struct virtio_gpu_transfer_host_3d *cmd_p;
>  	struct virtio_gpu_vbuffer *vbuf;
> -	bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);
>  	struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo);
>  
> -	if (use_dma_api)
> -		dma_sync_sg_for_device(vgdev->vdev->dev.parent,
> -				       shmem->pages->sgl, shmem->pages->nents,
> -				       DMA_TO_DEVICE);
> +	dma_sync_sg_for_device(vgdev->vdev->dev.parent,
> +			       shmem->pages->sgl, shmem->pages->nents,
> +			       DMA_TO_DEVICE);
>  
>  	cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p));
>  	memset(cmd_p, 0, sizeof(*cmd_p));
> -- 
> 2.27.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch