1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (c) 2019, Linaro Limited
4 */
5
6 #include <dm.h>
7 #include <log.h>
8 #include <rng.h>
9 #include <virtio_types.h>
10 #include <virtio.h>
11 #include <virtio_ring.h>
12
13 #define BUFFER_SIZE 16UL
14
15 struct virtio_rng_priv {
16 struct virtqueue *rng_vq;
17 };
18
virtio_rng_read(struct udevice * dev,void * data,size_t len)19 static int virtio_rng_read(struct udevice *dev, void *data, size_t len)
20 {
21 int ret;
22 unsigned int rsize = 1;
23 unsigned char buf[BUFFER_SIZE] __aligned(4);
24 unsigned char *ptr = data;
25 struct virtio_sg sg;
26 struct virtio_sg *sgs[1];
27 struct virtio_rng_priv *priv = dev_get_priv(dev);
28
29 while (len) {
30 sg.addr = buf;
31 /*
32 * Work around implementations which always return 8 bytes
33 * less than requested, down to 0 bytes, which would
34 * cause an endless loop otherwise.
35 */
36 sg.length = min(rsize ? len : len + 8, sizeof(buf));
37 sgs[0] = &sg;
38
39 ret = virtqueue_add(priv->rng_vq, sgs, 0, 1);
40 if (ret)
41 return ret;
42
43 virtqueue_kick(priv->rng_vq);
44
45 while (!virtqueue_get_buf(priv->rng_vq, &rsize))
46 ;
47
48 if (rsize > sg.length)
49 return -EIO;
50
51 memcpy(ptr, buf, rsize);
52 len -= rsize;
53 ptr += rsize;
54 }
55
56 return 0;
57 }
58
virtio_rng_bind(struct udevice * dev)59 static int virtio_rng_bind(struct udevice *dev)
60 {
61 struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(dev->parent);
62
63 /* Indicate what driver features we support */
64 virtio_driver_features_init(uc_priv, NULL, 0, NULL, 0);
65
66 return 0;
67 }
68
virtio_rng_probe(struct udevice * dev)69 static int virtio_rng_probe(struct udevice *dev)
70 {
71 struct virtio_rng_priv *priv = dev_get_priv(dev);
72 int ret;
73
74 ret = virtio_find_vqs(dev, 1, &priv->rng_vq);
75 if (ret < 0) {
76 debug("%s: virtio_find_vqs failed\n", __func__);
77 return ret;
78 }
79
80 return 0;
81 }
82
83 static const struct dm_rng_ops virtio_rng_ops = {
84 .read = virtio_rng_read,
85 };
86
87 U_BOOT_DRIVER(virtio_rng) = {
88 .name = VIRTIO_RNG_DRV_NAME,
89 .id = UCLASS_RNG,
90 .bind = virtio_rng_bind,
91 .probe = virtio_rng_probe,
92 .remove = virtio_reset,
93 .ops = &virtio_rng_ops,
94 .priv_auto = sizeof(struct virtio_rng_priv),
95 .flags = DM_FLAG_ACTIVE_DMA,
96 };
97