/*
 * Intel MIC Platform Software Stack (MPSS)
 *
 * Copyright(c) 2013 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * The full GNU General Public License is included in this distribution in
 * the file called "COPYING".
 *
 * Disclaimer: The codes contained in these modules may be specific to
 * the Intel Software Development Platform codenamed: Knights Ferry, and
 * the Intel product codenamed: Knights Corner, and are not backward
 * compatible with other Intel products. Additionally, Intel will NOT
 * support the codes or instruction set in future products.
 *
 * Adapted from:
 *
 * virtio for kvm on s390
 *
 * Copyright IBM Corp. 2008
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (version 2 only)
 * as published by the Free Software Foundation.
 *
 *    Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
 *
 * Intel MIC Card driver.
 *
 */
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/virtio_config.h>

#include "../common/mic_dev.h"
#include "mic_virtio.h"

#define VIRTIO_SUBCODE_64 0x0D00

#define MIC_MAX_VRINGS                4
struct mic_vdev {
	struct virtio_device vdev;
	struct mic_device_desc __iomem *desc;
	struct mic_device_ctrl __iomem *dc;
	struct mic_device *mdev;
	void __iomem *vr[MIC_MAX_VRINGS];
	int used_size[MIC_MAX_VRINGS];
	struct completion reset_done;
	struct mic_irq *virtio_cookie;
	int c2h_vdev_db;
};

static struct mic_irq *virtio_config_cookie;
#define to_micvdev(vd) container_of(vd, struct mic_vdev, vdev)

/* Helper API to obtain the parent of the virtio device */
static inline struct device *mic_dev(struct mic_vdev *mvdev)
{
	return mvdev->vdev.dev.parent;
}

/* This gets the device's feature bits. */
static u64 mic_get_features(struct virtio_device *vdev)
{
	unsigned int i, bits;
	u32 features = 0;
	struct mic_device_desc __iomem *desc = to_micvdev(vdev)->desc;
	u8 __iomem *in_features = mic_vq_features(desc);
	int feature_len = ioread8(&desc->feature_len);

	bits = min_t(unsigned, feature_len, sizeof(features)) * 8;
	for (i = 0; i < bits; i++)
		if (ioread8(&in_features[i / 8]) & (BIT(i % 8)))
			features |= BIT(i);

	return features;
}

static int mic_finalize_features(struct virtio_device *vdev)
{
	unsigned int i, bits;
	struct mic_device_desc __iomem *desc = to_micvdev(vdev)->desc;
	u8 feature_len = ioread8(&desc->feature_len);
	/* Second half of bitmap is features we accept. */
	u8 __iomem *out_features =
		mic_vq_features(desc) + feature_len;

	/* Give virtio_ring a chance to accept features. */
	vring_transport_features(vdev);

	/* Make sure we don't have any features > 32 bits! */
	BUG_ON((u32)vdev->features != vdev->features);

	memset_io(out_features, 0, feature_len);
	bits = min_t(unsigned, feature_len,
		sizeof(vdev->features)) * 8;
	for (i = 0; i < bits; i++) {
		if (__virtio_test_bit(vdev, i))
			iowrite8(ioread8(&out_features[i / 8]) | (1 << (i % 8)),
				 &out_features[i / 8]);
	}

	return 0;
}

/*
 * Reading and writing elements in config space
 */
static void mic_get(struct virtio_device *vdev, unsigned int offset,
		   void *buf, unsigned len)
{
	struct mic_device_desc __iomem *desc = to_micvdev(vdev)->desc;

	if (offset + len > ioread8(&desc->config_len))
		return;
	memcpy_fromio(buf, mic_vq_configspace(desc) + offset, len);
}

static void mic_set(struct virtio_device *vdev, unsigned int offset,
		   const void *buf, unsigned len)
{
	struct mic_device_desc __iomem *desc = to_micvdev(vdev)->desc;

	if (offset + len > ioread8(&desc->config_len))
		return;
	memcpy_toio(mic_vq_configspace(desc) + offset, buf, len);
}

/*
 * The operations to get and set the status word just access the status
 * field of the device descriptor. set_status also interrupts the host
 * to tell about status changes.
 */
static u8 mic_get_status(struct virtio_device *vdev)
{
	return ioread8(&to_micvdev(vdev)->desc->status);
}

static void mic_set_status(struct virtio_device *vdev, u8 status)
{
	struct mic_vdev *mvdev = to_micvdev(vdev);
	if (!status)
		return;
	iowrite8(status, &mvdev->desc->status);
	mic_send_intr(mvdev->mdev, mvdev->c2h_vdev_db);
}

/* Inform host on a virtio device reset and wait for ack from host */
static void mic_reset_inform_host(struct virtio_device *vdev)
{
	struct mic_vdev *mvdev = to_micvdev(vdev);
	struct mic_device_ctrl __iomem *dc = mvdev->dc;
	int retry;

	iowrite8(0, &dc->host_ack);
	iowrite8(1, &dc->vdev_reset);
	mic_send_intr(mvdev->mdev, mvdev->c2h_vdev_db);

	/* Wait till host completes all card accesses and acks the reset */
	for (retry = 100; retry--;) {
		if (ioread8(&dc->host_ack))
			break;
		msleep(100);
	};

	dev_dbg(mic_dev(mvdev), "%s: retry: %d\n", __func__, retry);

	/* Reset status to 0 in case we timed out */
	iowrite8(0, &mvdev->desc->status);
}

static void mic_reset(struct virtio_device *vdev)
{
	struct mic_vdev *mvdev = to_micvdev(vdev);

	dev_dbg(mic_dev(mvdev), "%s: virtio id %d\n",
		__func__, vdev->id.device);

	mic_reset_inform_host(vdev);
	complete_all(&mvdev->reset_done);
}

/*
 * The virtio_ring code calls this API when it wants to notify the Host.
 */
static bool mic_notify(struct virtqueue *vq)
{
	struct mic_vdev *mvdev = vq->priv;

	mic_send_intr(mvdev->mdev, mvdev->c2h_vdev_db);
	return true;
}

static void mic_del_vq(struct virtqueue *vq, int n)
{
	struct mic_vdev *mvdev = to_micvdev(vq->vdev);
	struct vring *vr = (struct vring *)(vq + 1);

	free_pages((unsigned long) vr->used, get_order(mvdev->used_size[n]));
	vring_del_virtqueue(vq);
	mic_card_unmap(mvdev->mdev, mvdev->vr[n]);
	mvdev->vr[n] = NULL;
}

static void mic_del_vqs(struct virtio_device *vdev)
{
	struct mic_vdev *mvdev = to_micvdev(vdev);
	struct virtqueue *vq, *n;
	int idx = 0;

	dev_dbg(mic_dev(mvdev), "%s\n", __func__);

	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
		mic_del_vq(vq, idx++);
}

/*
 * This routine will assign vring's allocated in host/io memory. Code in
 * virtio_ring.c however continues to access this io memory as if it were local
 * memory without io accessors.
 */
static struct virtqueue *mic_find_vq(struct virtio_device *vdev,
				     unsigned index,
				     void (*callback)(struct virtqueue *vq),
				     const char *name)
{
	struct mic_vdev *mvdev = to_micvdev(vdev);
	struct mic_vqconfig __iomem *vqconfig;
	struct mic_vqconfig config;
	struct virtqueue *vq;
	void __iomem *va;
	struct _mic_vring_info __iomem *info;
	void *used;
	int vr_size, _vr_size, err, magic;
	struct vring *vr;
	u8 type = ioread8(&mvdev->desc->type);

	if (index >= ioread8(&mvdev->desc->num_vq))
		return ERR_PTR(-ENOENT);

	if (!name)
		return ERR_PTR(-ENOENT);

	/* First assign the vring's allocated in host memory */
	vqconfig = mic_vq_config(mvdev->desc) + index;
	memcpy_fromio(&config, vqconfig, sizeof(config));
	_vr_size = vring_size(le16_to_cpu(config.num), MIC_VIRTIO_RING_ALIGN);
	vr_size = PAGE_ALIGN(_vr_size + sizeof(struct _mic_vring_info));
	va = mic_card_map(mvdev->mdev, le64_to_cpu(config.address), vr_size);
	if (!va)
		return ERR_PTR(-ENOMEM);
	mvdev->vr[index] = va;
	memset_io(va, 0x0, _vr_size);
	vq = vring_new_virtqueue(index, le16_to_cpu(config.num),
				 MIC_VIRTIO_RING_ALIGN, vdev, false,
				 (void __force *)va, mic_notify, callback,
				 name);
	if (!vq) {
		err = -ENOMEM;
		goto unmap;
	}
	info = va + _vr_size;
	magic = ioread32(&info->magic);

	if (WARN(magic != MIC_MAGIC + type + index, "magic mismatch")) {
		err = -EIO;
		goto unmap;
	}

	/* Allocate and reassign used ring now */
	mvdev->used_size[index] = PAGE_ALIGN(sizeof(__u16) * 3 +
					     sizeof(struct vring_used_elem) *
					     le16_to_cpu(config.num));
	used = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
					get_order(mvdev->used_size[index]));
	if (!used) {
		err = -ENOMEM;
		dev_err(mic_dev(mvdev), "%s %d err %d\n",
			__func__, __LINE__, err);
		goto del_vq;
	}
	iowrite64(virt_to_phys(used), &vqconfig->used_address);

	/*
	 * To reassign the used ring here we are directly accessing
	 * struct vring_virtqueue which is a private data structure
	 * in virtio_ring.c. At the minimum, a BUILD_BUG_ON() in
	 * vring_new_virtqueue() would ensure that
	 *  (&vq->vring == (struct vring *) (&vq->vq + 1));
	 */
	vr = (struct vring *)(vq + 1);
	vr->used = used;

	vq->priv = mvdev;
	return vq;
del_vq:
	vring_del_virtqueue(vq);
unmap:
	mic_card_unmap(mvdev->mdev, mvdev->vr[index]);
	return ERR_PTR(err);
}

static int mic_find_vqs(struct virtio_device *vdev, unsigned nvqs,
			struct virtqueue *vqs[],
			vq_callback_t *callbacks[],
			const char *names[])
{
	struct mic_vdev *mvdev = to_micvdev(vdev);
	struct mic_device_ctrl __iomem *dc = mvdev->dc;
	int i, err, retry;

	/* We must have this many virtqueues. */
	if (nvqs > ioread8(&mvdev->desc->num_vq))
		return -ENOENT;

	for (i = 0; i < nvqs; ++i) {
		dev_dbg(mic_dev(mvdev), "%s: %d: %s\n",
			__func__, i, names[i]);
		vqs[i] = mic_find_vq(vdev, i, callbacks[i], names[i]);
		if (IS_ERR(vqs[i])) {
			err = PTR_ERR(vqs[i]);
			goto error;
		}
	}

	iowrite8(1, &dc->used_address_updated);
	/*
	 * Send an interrupt to the host to inform it that used
	 * rings have been re-assigned.
	 */
	mic_send_intr(mvdev->mdev, mvdev->c2h_vdev_db);
	for (retry = 100; retry--;) {
		if (!ioread8(&dc->used_address_updated))
			break;
		msleep(100);
	};

	dev_dbg(mic_dev(mvdev), "%s: retry: %d\n", __func__, retry);
	if (!retry) {
		err = -ENODEV;
		goto error;
	}

	return 0;
error:
	mic_del_vqs(vdev);
	return err;
}

/*
 * The config ops structure as defined by virtio config
 */
static struct virtio_config_ops mic_vq_config_ops = {
	.get_features = mic_get_features,
	.finalize_features = mic_finalize_features,
	.get = mic_get,
	.set = mic_set,
	.get_status = mic_get_status,
	.set_status = mic_set_status,
	.reset = mic_reset,
	.find_vqs = mic_find_vqs,
	.del_vqs = mic_del_vqs,
};

static irqreturn_t
mic_virtio_intr_handler(int irq, void *data)
{
	struct mic_vdev *mvdev = data;
	struct virtqueue *vq;

	mic_ack_interrupt(mvdev->mdev);
	list_for_each_entry(vq, &mvdev->vdev.vqs, list)
		vring_interrupt(0, vq);

	return IRQ_HANDLED;
}

static void mic_virtio_release_dev(struct device *_d)
{
	/*
	 * No need for a release method similar to virtio PCI.
	 * Provide an empty one to avoid getting a warning from core.
	 */
}

/*
 * adds a new device and register it with virtio
 * appropriate drivers are loaded by the device model
 */
static int mic_add_device(struct mic_device_desc __iomem *d,
	unsigned int offset, struct mic_driver *mdrv)
{
	struct mic_vdev *mvdev;
	int ret;
	int virtio_db;
	u8 type = ioread8(&d->type);

	mvdev = kzalloc(sizeof(*mvdev), GFP_KERNEL);
	if (!mvdev) {
		dev_err(mdrv->dev, "Cannot allocate mic dev %u type %u\n",
			offset, type);
		return -ENOMEM;
	}

	mvdev->mdev = &mdrv->mdev;
	mvdev->vdev.dev.parent = mdrv->dev;
	mvdev->vdev.dev.release = mic_virtio_release_dev;
	mvdev->vdev.id.device = type;
	mvdev->vdev.config = &mic_vq_config_ops;
	mvdev->desc = d;
	mvdev->dc = (void __iomem *)d + mic_aligned_desc_size(d);
	init_completion(&mvdev->reset_done);

	virtio_db = mic_next_card_db();
	mvdev->virtio_cookie = mic_request_card_irq(mic_virtio_intr_handler,
			NULL, "virtio intr", mvdev, virtio_db);
	if (IS_ERR(mvdev->virtio_cookie)) {
		ret = PTR_ERR(mvdev->virtio_cookie);
		goto kfree;
	}
	iowrite8((u8)virtio_db, &mvdev->dc->h2c_vdev_db);
	mvdev->c2h_vdev_db = ioread8(&mvdev->dc->c2h_vdev_db);

	ret = register_virtio_device(&mvdev->vdev);
	if (ret) {
		dev_err(mic_dev(mvdev),
			"Failed to register mic device %u type %u\n",
			offset, type);
		goto free_irq;
	}
	iowrite64((u64)mvdev, &mvdev->dc->vdev);
	dev_dbg(mic_dev(mvdev), "%s: registered mic device %u type %u mvdev %p\n",
		__func__, offset, type, mvdev);

	return 0;

free_irq:
	mic_free_card_irq(mvdev->virtio_cookie, mvdev);
kfree:
	kfree(mvdev);
	return ret;
}

/*
 * match for a mic device with a specific desc pointer
 */
static int mic_match_desc(struct device *dev, void *data)
{
	struct virtio_device *vdev = dev_to_virtio(dev);
	struct mic_vdev *mvdev = to_micvdev(vdev);

	return mvdev->desc == (void __iomem *)data;
}

static void mic_handle_config_change(struct mic_device_desc __iomem *d,
	unsigned int offset, struct mic_driver *mdrv)
{
	struct mic_device_ctrl __iomem *dc
		= (void __iomem *)d + mic_aligned_desc_size(d);
	struct mic_vdev *mvdev = (struct mic_vdev *)ioread64(&dc->vdev);

	if (ioread8(&dc->config_change) != MIC_VIRTIO_PARAM_CONFIG_CHANGED)
		return;

	dev_dbg(mdrv->dev, "%s %d\n", __func__, __LINE__);
	virtio_config_changed(&mvdev->vdev);
	iowrite8(1, &dc->guest_ack);
}

/*
 * removes a virtio device if a hot remove event has been
 * requested by the host.
 */
static int mic_remove_device(struct mic_device_desc __iomem *d,
	unsigned int offset, struct mic_driver *mdrv)
{
	struct mic_device_ctrl __iomem *dc
		= (void __iomem *)d + mic_aligned_desc_size(d);
	struct mic_vdev *mvdev = (struct mic_vdev *)ioread64(&dc->vdev);
	u8 status;
	int ret = -1;

	if (ioread8(&dc->config_change) == MIC_VIRTIO_PARAM_DEV_REMOVE) {
		dev_dbg(mdrv->dev,
			"%s %d config_change %d type %d mvdev %p\n",
			__func__, __LINE__,
			ioread8(&dc->config_change), ioread8(&d->type), mvdev);

		status = ioread8(&d->status);
		reinit_completion(&mvdev->reset_done);
		unregister_virtio_device(&mvdev->vdev);
		mic_free_card_irq(mvdev->virtio_cookie, mvdev);
		if (status & VIRTIO_CONFIG_S_DRIVER_OK)
			wait_for_completion(&mvdev->reset_done);
		kfree(mvdev);
		iowrite8(1, &dc->guest_ack);
		dev_dbg(mdrv->dev, "%s %d guest_ack %d\n",
			__func__, __LINE__, ioread8(&dc->guest_ack));
		ret = 0;
	}

	return ret;
}

#define REMOVE_DEVICES true

static void mic_scan_devices(struct mic_driver *mdrv, bool remove)
{
	s8 type;
	unsigned int i;
	struct mic_device_desc __iomem *d;
	struct mic_device_ctrl __iomem *dc;
	struct device *dev;
	int ret;

	for (i = sizeof(struct mic_bootparam); i < MIC_DP_SIZE;
		i += mic_total_desc_size(d)) {
		d = mdrv->dp + i;
		dc = (void __iomem *)d + mic_aligned_desc_size(d);
		/*
		 * This read barrier is paired with the corresponding write
		 * barrier on the host which is inserted before adding or
		 * removing a virtio device descriptor, by updating the type.
		 */
		rmb();
		type = ioread8(&d->type);

		/* end of list */
		if (type == 0)
			break;

		if (type == -1)
			continue;

		/* device already exists */
		dev = device_find_child(mdrv->dev, (void __force *)d,
					mic_match_desc);
		if (dev) {
			if (remove)
				iowrite8(MIC_VIRTIO_PARAM_DEV_REMOVE,
					 &dc->config_change);
			put_device(dev);
			mic_handle_config_change(d, i, mdrv);
			ret = mic_remove_device(d, i, mdrv);
			if (!ret && !remove)
				iowrite8(-1, &d->type);
			if (remove) {
				iowrite8(0, &dc->config_change);
				iowrite8(0, &dc->guest_ack);
			}
			continue;
		}

		/* new device */
		dev_dbg(mdrv->dev, "%s %d Adding new virtio device %p\n",
			__func__, __LINE__, d);
		if (!remove)
			mic_add_device(d, i, mdrv);
	}
}

/*
 * mic_hotplug_device tries to find changes in the device page.
 */
static void mic_hotplug_devices(struct work_struct *work)
{
	struct mic_driver *mdrv = container_of(work,
		struct mic_driver, hotplug_work);

	mic_scan_devices(mdrv, !REMOVE_DEVICES);
}

/*
 * Interrupt handler for hot plug/config changes etc.
 */
static irqreturn_t
mic_extint_handler(int irq, void *data)
{
	struct mic_driver *mdrv = (struct mic_driver *)data;

	dev_dbg(mdrv->dev, "%s %d hotplug work\n",
		__func__, __LINE__);
	mic_ack_interrupt(&mdrv->mdev);
	schedule_work(&mdrv->hotplug_work);
	return IRQ_HANDLED;
}

/*
 * Init function for virtio
 */
int mic_devices_init(struct mic_driver *mdrv)
{
	int rc;
	struct mic_bootparam __iomem *bootparam;
	int config_db;

	INIT_WORK(&mdrv->hotplug_work, mic_hotplug_devices);
	mic_scan_devices(mdrv, !REMOVE_DEVICES);

	config_db = mic_next_card_db();
	virtio_config_cookie = mic_request_card_irq(mic_extint_handler, NULL,
						    "virtio_config_intr", mdrv,
						    config_db);
	if (IS_ERR(virtio_config_cookie)) {
		rc = PTR_ERR(virtio_config_cookie);
		goto exit;
	}

	bootparam = mdrv->dp;
	iowrite8(config_db, &bootparam->h2c_config_db);
	return 0;
exit:
	return rc;
}

/*
 * Uninit function for virtio
 */
void mic_devices_uninit(struct mic_driver *mdrv)
{
	struct mic_bootparam __iomem *bootparam = mdrv->dp;
	iowrite8(-1, &bootparam->h2c_config_db);
	mic_free_card_irq(virtio_config_cookie, mdrv);
	flush_work(&mdrv->hotplug_work);
	mic_scan_devices(mdrv, REMOVE_DEVICES);
}