[RFC PATCH 02/12] virtio/s390: DMA support for virtio-ccw

[Halil Pasic <pasic@linux.ibm.com>]

Currently we have a problem if a virtio-ccw device has
VIRTIO_F_IOMMU_PLATFORM. In future we do want to support DMA API with
virtio-ccw.

Let us do the plumbing, so the feature VIRTIO_F_IOMMU_PLATFORM works
with virtio-ccw.

Let us also switch from legacy avail/used accessors to the DMA aware
ones (even if it isn't strictly necessary).

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
---
 drivers/s390/virtio/virtio_ccw.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index edf4afe2d688..5956c9e820bb 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -66,6 +66,7 @@ struct virtio_ccw_device {
 	bool device_lost;
 	unsigned int config_ready;
 	void *airq_info;
+	__u64 dma_mask;
 };
 
 struct vq_info_block_legacy {
@@ -536,8 +537,8 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
 		info->info_block->s.desc = queue;
 		info->info_block->s.index = i;
 		info->info_block->s.num = info->num;
-		info->info_block->s.avail = (__u64)virtqueue_get_avail(vq);
-		info->info_block->s.used = (__u64)virtqueue_get_used(vq);
+		info->info_block->s.avail = (__u64)virtqueue_get_avail_addr(vq);
+		info->info_block->s.used = (__u64)virtqueue_get_used_addr(vq);
 		ccw->count = sizeof(info->info_block->s);
 	}
 	ccw->cmd_code = CCW_CMD_SET_VQ;
@@ -769,10 +770,8 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
 static void ccw_transport_features(struct virtio_device *vdev)
 {
 	/*
-	 * Packed ring isn't enabled on virtio_ccw for now,
-	 * because virtio_ccw uses some legacy accessors,
-	 * e.g. virtqueue_get_avail() and virtqueue_get_used()
-	 * which aren't available in packed ring currently.
+	 * There shouldn't be anything that precludes supporting paced.
+	 * TODO: Remove the limitation after having another look into this.
 	 */
 	__virtio_clear_bit(vdev, VIRTIO_F_RING_PACKED);
 }
@@ -1255,6 +1254,18 @@ static int virtio_ccw_online(struct ccw_device *cdev)
 		ret = -ENOMEM;
 		goto out_free;
 	}
+	vcdev->vdev.dev.parent = &cdev->dev;
+	cdev->dev.dma_mask = &vcdev->dma_mask;
+
+	ret = dma_set_mask_and_coherent(&cdev->dev, DMA_BIT_MASK(64));
+	if (ret)
+		ret = dma_set_mask_and_coherent(&cdev->dev,
+						DMA_BIT_MASK(32));
+	if (ret) {
+		dev_warn(&cdev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");
+		goto out_free;
+	}
+
 	vcdev->config_block = kzalloc(sizeof(*vcdev->config_block),
 				   GFP_DMA | GFP_KERNEL);
 	if (!vcdev->config_block) {
-- 
2.16.4