diff --git a/MAINTAINERS b/MAINTAINERS
index a61f4f3b78a91f13e25826d1b407e9ccbbb48cf8..db1c7b74642e66899262b5549e0d212ae82fca12 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17940,6 +17940,7 @@ F: drivers/regulator/scmi-regulator.c
F: drivers/reset/reset-scmi.c
F: include/linux/sc[mp]i_protocol.h
F: include/trace/events/scmi.h
+F: include/uapi/linux/virtio_scmi.h
SYSTEM RESET/SHUTDOWN DRIVERS
M: Sebastian Reichel <sre@kernel.org>
diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig
index 24fed705b02c829c3e2521322453085221d3f04c..7f4d2435503b8ad2e650bce50c0cfc8e1cf616b9 100644
--- a/drivers/firmware/arm_scmi/Kconfig
+++ b/drivers/firmware/arm_scmi/Kconfig
@@ -66,6 +66,17 @@ config ARM_SCMI_TRANSPORT_SMC
If you want the ARM SCMI PROTOCOL stack to include support for a
transport based on SMC, answer Y.
+config ARM_SCMI_TRANSPORT_VIRTIO
+ bool "SCMI transport based on VirtIO"
+ depends on VIRTIO
+ select ARM_SCMI_HAVE_TRANSPORT
+ select ARM_SCMI_HAVE_MSG
+ help
+ This enables the virtio based transport for SCMI.
+
+ If you want the ARM SCMI PROTOCOL stack to include support for a
+ transport based on VirtIO, answer Y.
+
endif #ARM_SCMI_PROTOCOL
config ARM_SCMI_POWER_DOMAIN
diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index aaad9f6589aa7900a0d90f8d883b203044b22b2f..1dcf123d64abc02eba59d73ffa4aebe922a387bd 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -5,6 +5,7 @@ scmi-transport-$(CONFIG_ARM_SCMI_HAVE_SHMEM) = shmem.o
scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_MAILBOX) += mailbox.o
scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_SMC) += smc.o
scmi-transport-$(CONFIG_ARM_SCMI_HAVE_MSG) += msg.o
+scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_VIRTIO) += virtio.o
scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o
scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
$(scmi-transport-y)
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 7864c21269b090ed5cb7d929f0e0493a585cb8b5..dea1bfbe10527c593caff1934c903475ead6ecd1 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -418,6 +418,9 @@ extern const struct scmi_desc scmi_mailbox_desc;
#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
extern const struct scmi_desc scmi_smc_desc;
#endif
+#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
+extern const struct scmi_desc scmi_virtio_desc;
+#endif
void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr, void *priv);
void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id);
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index aaca01a4d75217fb610c11863bad2395a3bb1d97..00fcacd06562803b5e47950e8366b1f3ca165435 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -1983,6 +1983,9 @@ static const struct of_device_id scmi_of_match[] = {
#endif
#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
+#endif
+#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
+ { .compatible = "arm,scmi-virtio", .data = &scmi_virtio_desc},
#endif
{ /* Sentinel */ },
};
diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c
new file mode 100644
index 0000000000000000000000000000000000000000..3dacf794b177c4286a047cc2d28f42cebbb7099d
--- /dev/null
+++ b/drivers/firmware/arm_scmi/virtio.c
@@ -0,0 +1,491 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Virtio Transport driver for Arm System Control and Management Interface
+ * (SCMI).
+ *
+ * Copyright (C) 2020-2021 OpenSynergy.
+ * Copyright (C) 2021 ARM Ltd.
+ */
+
+/**
+ * DOC: Theory of Operation
+ *
+ * The scmi-virtio transport implements a driver for the virtio SCMI device.
+ *
+ * There is one Tx channel (virtio cmdq, A2P channel) and at most one Rx
+ * channel (virtio eventq, P2A channel). Each channel is implemented through a
+ * virtqueue. Access to each virtqueue is protected by spinlocks.
+ */
+
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+
+#include <uapi/linux/virtio_ids.h>
+#include <uapi/linux/virtio_scmi.h>
+
+#include "common.h"
+
+#define VIRTIO_SCMI_MAX_MSG_SIZE 128 /* Value may be increased. */
+#define VIRTIO_SCMI_MAX_PDU_SIZE \
+ (VIRTIO_SCMI_MAX_MSG_SIZE + SCMI_MSG_MAX_PROT_OVERHEAD)
+#define DESCRIPTORS_PER_TX_MSG 2
+
+/**
+ * struct scmi_vio_channel - Transport channel information
+ *
+ * @vqueue: Associated virtqueue
+ * @cinfo: SCMI Tx or Rx channel
+ * @free_list: List of unused scmi_vio_msg, maintained for Tx channels only
+ * @is_rx: Whether channel is an Rx channel
+ * @ready: Whether transport user is ready to hear about channel
+ * @max_msg: Maximum number of pending messages for this channel.
+ * @lock: Protects access to all members except ready.
+ * @ready_lock: Protects access to ready. If required, it must be taken before
+ * lock.
+ */
+struct scmi_vio_channel {
+ struct virtqueue *vqueue;
+ struct scmi_chan_info *cinfo;
+ struct list_head free_list;
+ bool is_rx;
+ bool ready;
+ unsigned int max_msg;
+ /* lock to protect access to all members except ready. */
+ spinlock_t lock;
+ /* lock to rotects access to ready flag. */
+ spinlock_t ready_lock;
+};
+
+/**
+ * struct scmi_vio_msg - Transport PDU information
+ *
+ * @request: SDU used for commands
+ * @input: SDU used for (delayed) responses and notifications
+ * @list: List which scmi_vio_msg may be part of
+ * @rx_len: Input SDU size in bytes, once input has been received
+ */
+struct scmi_vio_msg {
+ struct scmi_msg_payld *request;
+ struct scmi_msg_payld *input;
+ struct list_head list;
+ unsigned int rx_len;
+};
+
+/* Only one SCMI VirtIO device can possibly exist */
+static struct virtio_device *scmi_vdev;
+
+static bool scmi_vio_have_vq_rx(struct virtio_device *vdev)
+{
+ return virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);
+}
+
+static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch,
+ struct scmi_vio_msg *msg)
+{
+ struct scatterlist sg_in;
+ int rc;
+ unsigned long flags;
+
+ sg_init_one(&sg_in, msg->input, VIRTIO_SCMI_MAX_PDU_SIZE);
+
+ spin_lock_irqsave(&vioch->lock, flags);
+
+ rc = virtqueue_add_inbuf(vioch->vqueue, &sg_in, 1, msg, GFP_ATOMIC);
+ if (rc)
+ dev_err_once(vioch->cinfo->dev,
+ "failed to add to virtqueue (%d)\n", rc);
+ else
+ virtqueue_kick(vioch->vqueue);
+
+ spin_unlock_irqrestore(&vioch->lock, flags);
+
+ return rc;
+}
+
+static void scmi_finalize_message(struct scmi_vio_channel *vioch,
+ struct scmi_vio_msg *msg)
+{
+ if (vioch->is_rx) {
+ scmi_vio_feed_vq_rx(vioch, msg);
+ } else {
+ unsigned long flags;
+
+ spin_lock_irqsave(&vioch->lock, flags);
+ list_add(&msg->list, &vioch->free_list);
+ spin_unlock_irqrestore(&vioch->lock, flags);
+ }
+}
+
+static void scmi_vio_complete_cb(struct virtqueue *vqueue)
+{
+ unsigned long ready_flags;
+ unsigned long flags;
+ unsigned int length;
+ struct scmi_vio_channel *vioch;
+ struct scmi_vio_msg *msg;
+ bool cb_enabled = true;
+
+ if (WARN_ON_ONCE(!vqueue->vdev->priv))
+ return;
+ vioch = &((struct scmi_vio_channel *)vqueue->vdev->priv)[vqueue->index];
+
+ for (;;) {
+ spin_lock_irqsave(&vioch->ready_lock, ready_flags);
+
+ if (!vioch->ready) {
+ if (!cb_enabled)
+ (void)virtqueue_enable_cb(vqueue);
+ goto unlock_ready_out;
+ }
+
+ spin_lock_irqsave(&vioch->lock, flags);
+ if (cb_enabled) {
+ virtqueue_disable_cb(vqueue);
+ cb_enabled = false;
+ }
+ msg = virtqueue_get_buf(vqueue, &length);
+ if (!msg) {
+ if (virtqueue_enable_cb(vqueue))
+ goto unlock_out;
+ cb_enabled = true;
+ }
+ spin_unlock_irqrestore(&vioch->lock, flags);
+
+ if (msg) {
+ msg->rx_len = length;
+ scmi_rx_callback(vioch->cinfo,
+ msg_read_header(msg->input), msg);
+
+ scmi_finalize_message(vioch, msg);
+ }
+
+ spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);
+ }
+
+unlock_out:
+ spin_unlock_irqrestore(&vioch->lock, flags);
+unlock_ready_out:
+ spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);
+}
+
+static const char *const scmi_vio_vqueue_names[] = { "tx", "rx" };
+
+static vq_callback_t *scmi_vio_complete_callbacks[] = {
+ scmi_vio_complete_cb,
+ scmi_vio_complete_cb
+};
+
+static unsigned int virtio_get_max_msg(struct scmi_chan_info *base_cinfo)
+{
+ struct scmi_vio_channel *vioch = base_cinfo->transport_info;
+
+ return vioch->max_msg;
+}
+
+static int virtio_link_supplier(struct device *dev)
+{
+ if (!scmi_vdev) {
+ dev_notice_once(dev,
+ "Deferring probe after not finding a bound scmi-virtio device\n");
+ return -EPROBE_DEFER;
+ }
+
+ if (!device_link_add(dev, &scmi_vdev->dev,
+ DL_FLAG_AUTOREMOVE_CONSUMER)) {
+ dev_err(dev, "Adding link to supplier virtio device failed\n");
+ return -ECANCELED;
+ }
+
+ return 0;
+}
+
+static bool virtio_chan_available(struct device *dev, int idx)
+{
+ struct scmi_vio_channel *channels, *vioch = NULL;
+
+ if (WARN_ON_ONCE(!scmi_vdev))
+ return false;
+
+ channels = (struct scmi_vio_channel *)scmi_vdev->priv;
+
+ switch (idx) {
+ case VIRTIO_SCMI_VQ_TX:
+ vioch = &channels[VIRTIO_SCMI_VQ_TX];
+ break;
+ case VIRTIO_SCMI_VQ_RX:
+ if (scmi_vio_have_vq_rx(scmi_vdev))
+ vioch = &channels[VIRTIO_SCMI_VQ_RX];
+ break;
+ default:
+ return false;
+ }
+
+ return vioch && !vioch->cinfo ? true : false;
+}
+
+static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
+ bool tx)
+{
+ unsigned long flags;
+ struct scmi_vio_channel *vioch;
+ int index = tx ? VIRTIO_SCMI_VQ_TX : VIRTIO_SCMI_VQ_RX;
+ int i;
+
+ if (!scmi_vdev)
+ return -EPROBE_DEFER;
+
+ vioch = &((struct scmi_vio_channel *)scmi_vdev->priv)[index];
+
+ for (i = 0; i < vioch->max_msg; i++) {
+ struct scmi_vio_msg *msg;
+
+ msg = devm_kzalloc(cinfo->dev, sizeof(*msg), GFP_KERNEL);
+ if (!msg)
+ return -ENOMEM;
+
+ if (tx) {
+ msg->request = devm_kzalloc(cinfo->dev,
+ VIRTIO_SCMI_MAX_PDU_SIZE,
+ GFP_KERNEL);
+ if (!msg->request)
+ return -ENOMEM;
+ }
+
+ msg->input = devm_kzalloc(cinfo->dev, VIRTIO_SCMI_MAX_PDU_SIZE,
+ GFP_KERNEL);
+ if (!msg->input)
+ return -ENOMEM;
+
+ if (tx) {
+ spin_lock_irqsave(&vioch->lock, flags);
+ list_add_tail(&msg->list, &vioch->free_list);
+ spin_unlock_irqrestore(&vioch->lock, flags);
+ } else {
+ scmi_vio_feed_vq_rx(vioch, msg);
+ }
+ }
+
+ spin_lock_irqsave(&vioch->lock, flags);
+ cinfo->transport_info = vioch;
+ /* Indirectly setting channel not available any more */
+ vioch->cinfo = cinfo;
+ spin_unlock_irqrestore(&vioch->lock, flags);
+
+ spin_lock_irqsave(&vioch->ready_lock, flags);
+ vioch->ready = true;
+ spin_unlock_irqrestore(&vioch->ready_lock, flags);
+
+ return 0;
+}
+
+static int virtio_chan_free(int id, void *p, void *data)
+{
+ unsigned long flags;
+ struct scmi_chan_info *cinfo = p;
+ struct scmi_vio_channel *vioch = cinfo->transport_info;
+
+ spin_lock_irqsave(&vioch->ready_lock, flags);
+ vioch->ready = false;
+ spin_unlock_irqrestore(&vioch->ready_lock, flags);
+
+ scmi_free_channel(cinfo, data, id);
+
+ spin_lock_irqsave(&vioch->lock, flags);
+ vioch->cinfo = NULL;
+ spin_unlock_irqrestore(&vioch->lock, flags);
+
+ return 0;
+}
+
+static int virtio_send_message(struct scmi_chan_info *cinfo,
+ struct scmi_xfer *xfer)
+{
+ struct scmi_vio_channel *vioch = cinfo->transport_info;
+ struct scatterlist sg_out;
+ struct scatterlist sg_in;
+ struct scatterlist *sgs[DESCRIPTORS_PER_TX_MSG] = { &sg_out, &sg_in };
+ unsigned long flags;
+ int rc;
+ struct scmi_vio_msg *msg;
+
+ spin_lock_irqsave(&vioch->lock, flags);
+
+ if (list_empty(&vioch->free_list)) {
+ spin_unlock_irqrestore(&vioch->lock, flags);
+ return -EBUSY;
+ }
+
+ msg = list_first_entry(&vioch->free_list, typeof(*msg), list);
+ list_del(&msg->list);
+
+ msg_tx_prepare(msg->request, xfer);
+
+ sg_init_one(&sg_out, msg->request, msg_command_size(xfer));
+ sg_init_one(&sg_in, msg->input, msg_response_size(xfer));
+
+ rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, msg, GFP_ATOMIC);
+ if (rc) {
+ list_add(&msg->list, &vioch->free_list);
+ dev_err_once(vioch->cinfo->dev,
+ "%s() failed to add to virtqueue (%d)\n", __func__,
+ rc);
+ } else {
+ virtqueue_kick(vioch->vqueue);
+ }
+
+ spin_unlock_irqrestore(&vioch->lock, flags);
+
+ return rc;
+}
+
+static void virtio_fetch_response(struct scmi_chan_info *cinfo,
+ struct scmi_xfer *xfer)
+{
+ struct scmi_vio_msg *msg = xfer->priv;
+
+ if (msg) {
+ msg_fetch_response(msg->input, msg->rx_len, xfer);
+ xfer->priv = NULL;
+ }
+}
+
+static void virtio_fetch_notification(struct scmi_chan_info *cinfo,
+ size_t max_len, struct scmi_xfer *xfer)
+{
+ struct scmi_vio_msg *msg = xfer->priv;
+
+ if (msg) {
+ msg_fetch_notification(msg->input, msg->rx_len, max_len, xfer);
+ xfer->priv = NULL;
+ }
+}
+
+static const struct scmi_transport_ops scmi_virtio_ops = {
+ .link_supplier = virtio_link_supplier,
+ .chan_available = virtio_chan_available,
+ .chan_setup = virtio_chan_setup,
+ .chan_free = virtio_chan_free,
+ .get_max_msg = virtio_get_max_msg,
+ .send_message = virtio_send_message,
+ .fetch_response = virtio_fetch_response,
+ .fetch_notification = virtio_fetch_notification,
+};
+
+static int scmi_vio_probe(struct virtio_device *vdev)
+{
+ struct device *dev = &vdev->dev;
+ struct scmi_vio_channel *channels;
+ bool have_vq_rx;
+ int vq_cnt;
+ int i;
+ int ret;
+ struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
+
+ /* Only one SCMI VirtiO device allowed */
+ if (scmi_vdev)
+ return -EINVAL;
+
+ have_vq_rx = scmi_vio_have_vq_rx(vdev);
+ vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
+
+ channels = devm_kcalloc(dev, vq_cnt, sizeof(*channels), GFP_KERNEL);
+ if (!channels)
+ return -ENOMEM;
+
+ if (have_vq_rx)
+ channels[VIRTIO_SCMI_VQ_RX].is_rx = true;
+
+ ret = virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks,
+ scmi_vio_vqueue_names, NULL);
+ if (ret) {
+ dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt);
+ return ret;
+ }
+
+ for (i = 0; i < vq_cnt; i++) {
+ unsigned int sz;
+
+ spin_lock_init(&channels[i].lock);
+ spin_lock_init(&channels[i].ready_lock);
+ INIT_LIST_HEAD(&channels[i].free_list);
+ channels[i].vqueue = vqs[i];
+
+ sz = virtqueue_get_vring_size(channels[i].vqueue);
+ /* Tx messages need multiple descriptors. */
+ if (!channels[i].is_rx)
+ sz /= DESCRIPTORS_PER_TX_MSG;
+
+ if (sz > MSG_TOKEN_MAX) {
+ dev_info_once(dev,
+ "%s virtqueue could hold %d messages. Only %ld allowed to be pending.\n",
+ channels[i].is_rx ? "rx" : "tx",
+ sz, MSG_TOKEN_MAX);
+ sz = MSG_TOKEN_MAX;
+ }
+ channels[i].max_msg = sz;
+ }
+
+ vdev->priv = channels;
+ scmi_vdev = vdev;
+
+ return 0;
+}
+
+static void scmi_vio_remove(struct virtio_device *vdev)
+{
+ vdev->config->reset(vdev);
+ vdev->config->del_vqs(vdev);
+ scmi_vdev = NULL;
+}
+
+static int scmi_vio_validate(struct virtio_device *vdev)
+{
+ if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+ dev_err(&vdev->dev,
+ "device does not comply with spec version 1.x\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static unsigned int features[] = {
+ VIRTIO_SCMI_F_P2A_CHANNELS,
+};
+
+static const struct virtio_device_id id_table[] = {
+ { VIRTIO_ID_SCMI, VIRTIO_DEV_ANY_ID },
+ { 0 }
+};
+
+static struct virtio_driver virtio_scmi_driver = {
+ .driver.name = "scmi-virtio",
+ .driver.owner = THIS_MODULE,
+ .feature_table = features,
+ .feature_table_size = ARRAY_SIZE(features),
+ .id_table = id_table,
+ .probe = scmi_vio_probe,
+ .remove = scmi_vio_remove,
+ .validate = scmi_vio_validate,
+};
+
+static int __init virtio_scmi_init(void)
+{
+ return register_virtio_driver(&virtio_scmi_driver);
+}
+
+static void __exit virtio_scmi_exit(void)
+{
+ unregister_virtio_driver(&virtio_scmi_driver);
+}
+
+const struct scmi_desc scmi_virtio_desc = {
+ .transport_init = virtio_scmi_init,
+ .transport_exit = virtio_scmi_exit,
+ .ops = &scmi_virtio_ops,
+ .max_rx_timeout_ms = 60000, /* for non-realtime virtio devices */
+ .max_msg = 0, /* overridden by virtio_get_max_msg() */
+ .max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE,
+};
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 70a8057ad4bbe195c3a565e2f87c6839c8b8c832..f74155f6882d82473db08944716f4ce84bedf6a0 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -55,6 +55,7 @@
#define VIRTIO_ID_FS 26 /* virtio filesystem */
#define VIRTIO_ID_PMEM 27 /* virtio pmem */
#define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
+#define VIRTIO_ID_SCMI 32 /* virtio SCMI */
#define VIRTIO_ID_BT 40 /* virtio bluetooth */
/*
diff --git a/include/uapi/linux/virtio_scmi.h b/include/uapi/linux/virtio_scmi.h
new file mode 100644
index 0000000000000000000000000000000000000000..f8ddd04a3ace9c3781704568a88167fe820cfb0d
--- /dev/null
+++ b/include/uapi/linux/virtio_scmi.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/*
+ * Copyright (C) 2020-2021 OpenSynergy GmbH
+ * Copyright (C) 2021 ARM Ltd.
+ */
+
+#ifndef _UAPI_LINUX_VIRTIO_SCMI_H
+#define _UAPI_LINUX_VIRTIO_SCMI_H
+
+#include <linux/virtio_types.h>
+
+/* Device implements some SCMI notifications, or delayed responses. */
+#define VIRTIO_SCMI_F_P2A_CHANNELS 0
+
+/* Device implements any SCMI statistics shared memory region */
+#define VIRTIO_SCMI_F_SHARED_MEMORY 1
+
+/* Virtqueues */
+
+#define VIRTIO_SCMI_VQ_TX 0 /* cmdq */
+#define VIRTIO_SCMI_VQ_RX 1 /* eventq */
+#define VIRTIO_SCMI_VQ_MAX_CNT 2
+
+#endif /* _UAPI_LINUX_VIRTIO_SCMI_H */