// SPDX-License-Identifier: GPL-2.0+

/*

 * Copyright (c) 2019, Linaro Limited

 */

#include <dm.h>

#include <log.h>

#include <rng.h>

#include <virtio_types.h>

#include <virtio.h>

#include <virtio_ring.h>

#define BUFFER_SIZE 16UL

struct virtio_rng_priv {

  struct virtqueue *rng_vq;

};

static int virtio_rng_read(struct udevice *dev, void *data, size_t len)

{

  int ret;

  unsigned int rsize = 1;

  unsigned char buf[BUFFER_SIZE] __aligned(4);

  unsigned char *ptr = data;

  struct virtio_sg sg;

  struct virtio_sg *sgs[1];

  struct virtio_rng_priv *priv = dev_get_priv(dev);

  while (len) {

    sg.addr = buf;

    /*

     * Work around implementations which always return 8 bytes

     * less than requested, down to 0 bytes, which would

     * cause an endless loop otherwise.

     */

    sg.length = min(rsize ? len : len + 8, sizeof(buf));

    sgs[0] = &sg;

    ret = virtqueue_add(priv->rng_vq, sgs, 0, 1);

    if (ret)

      return ret;

    virtqueue_kick(priv->rng_vq);

    while (!virtqueue_get_buf(priv->rng_vq, &rsize))

      ;

    if (rsize > sg.length)

      return -EIO;

    memcpy(ptr, buf, rsize);

    len -= rsize;

    ptr += rsize;

  }

  return 0;

}

static int virtio_rng_bind(struct udevice *dev)

{

  struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(dev->parent);

  /* Indicate what driver features we support */

  virtio_driver_features_init(uc_priv, NULL, 0, NULL, 0);

  return 0;

}

static int virtio_rng_probe(struct udevice *dev)

{

  struct virtio_rng_priv *priv = dev_get_priv(dev);

  int ret;

  ret = virtio_find_vqs(dev, 1, &priv->rng_vq);

  if (ret < 0) {

    debug("%s: virtio_find_vqs failed\n", __func__);

    return ret;

  }

  return 0;

}

static const struct dm_rng_ops virtio_rng_ops = {

  .read = virtio_rng_read,

};

U_BOOT_DRIVER(virtio_rng) = {

  .name = VIRTIO_RNG_DRV_NAME,

  .id = UCLASS_RNG,

  .bind = virtio_rng_bind,

  .probe  = virtio_rng_probe,

  .remove = virtio_reset,

  .ops  = &virtio_rng_ops,

  .priv_auto  = sizeof(struct virtio_rng_priv),

  .flags  = DM_FLAG_ACTIVE_DMA,

};