Re: [RFC PATCH 1/4] Add a RPMSG driver for the APU in the mt8183

[Mathieu Poirier]

Hi Alexandre,

On Wed, Sep 30, 2020 at 01:53:47PM +0200, Alexandre Bailon wrote:
> This adds a driver to communicate with the APU available
> in the mt8183. The driver is generic and could be used for other APU.
> It mostly provides a userspace interface to send messages and
> and share big buffers with the APU.
> 
> Signed-off-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
> ---
>  drivers/rpmsg/Kconfig          |   9 +
>  drivers/rpmsg/Makefile         |   1 +
>  drivers/rpmsg/apu_rpmsg.c      | 606 +++++++++++++++++++++++++++++++++
>  drivers/rpmsg/apu_rpmsg.h      |  52 +++
>  include/uapi/linux/apu_rpmsg.h |  36 ++
>  5 files changed, 704 insertions(+)
>  create mode 100644 drivers/rpmsg/apu_rpmsg.c
>  create mode 100644 drivers/rpmsg/apu_rpmsg.h
>  create mode 100644 include/uapi/linux/apu_rpmsg.h
> 
> diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
> index f96716893c2a..3437c6fc8647 100644
> --- a/drivers/rpmsg/Kconfig
> +++ b/drivers/rpmsg/Kconfig
> @@ -64,4 +64,13 @@ config RPMSG_VIRTIO
>  	select RPMSG
>  	select VIRTIO
>  
> +config RPMSG_APU
> +	tristate "APU RPMSG driver"
> +	help
> +	  This provides a RPMSG driver that provides some facilities to
> +	  communicate with an accelerated processing unit (APU).
> +	  This creates one or more char files that could be used by userspace
> +	  to send a message to an APU. In addition, this also take care of
> +	  sharing the memory buffer with the APU.
> +
>  endmenu
> diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
> index ffe932ef6050..93e0f3de99c9 100644
> --- a/drivers/rpmsg/Makefile
> +++ b/drivers/rpmsg/Makefile
> @@ -8,3 +8,4 @@ obj-$(CONFIG_RPMSG_QCOM_GLINK_RPM) += qcom_glink_rpm.o
>  obj-$(CONFIG_RPMSG_QCOM_GLINK_SMEM) += qcom_glink_smem.o
>  obj-$(CONFIG_RPMSG_QCOM_SMD)	+= qcom_smd.o
>  obj-$(CONFIG_RPMSG_VIRTIO)	+= virtio_rpmsg_bus.o
> +obj-$(CONFIG_RPMSG_APU)		+= apu_rpmsg.o
> diff --git a/drivers/rpmsg/apu_rpmsg.c b/drivers/rpmsg/apu_rpmsg.c
> new file mode 100644
> index 000000000000..5131b8b8e1f2
> --- /dev/null
> +++ b/drivers/rpmsg/apu_rpmsg.c
> @@ -0,0 +1,606 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// Copyright 2020 BayLibre SAS
> +
> +#include <linux/cdev.h>
> +#include <linux/dma-buf.h>
> +#include <linux/iommu.h>
> +#include <linux/iova.h>
> +#include <linux/types.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/remoteproc.h>
> +#include <linux/rpmsg.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include "rpmsg_internal.h"
> +
> +#include <uapi/linux/apu_rpmsg.h>
> +
> +#include "apu_rpmsg.h"
> +
> +/* Maximum of APU devices supported */
> +#define APU_DEV_MAX 2
> +
> +#define dev_to_apu(dev) container_of(dev, struct rpmsg_apu, dev)
> +#define cdev_to_apu(i_cdev) container_of(i_cdev, struct rpmsg_apu, cdev)
> +
> +struct rpmsg_apu {
> +	struct rpmsg_device *rpdev;
> +	struct cdev cdev;
> +	struct device dev;
> +
> +	struct rproc *rproc;
> +	struct iommu_domain *domain;
> +	struct iova_domain *iovad;
> +	int iova_limit_pfn;
> +};
> +
> +struct rpmsg_request {
> +	struct completion completion;
> +	struct list_head node;
> +	void *req;
> +};
> +
> +struct apu_buffer {
> +	int fd;
> +	struct dma_buf *dma_buf;
> +	struct dma_buf_attachment *attachment;
> +	struct sg_table *sg_table;
> +	u32 iova;
> +};
> +
> +/*
> + * Shared IOVA domain.
> + * The MT8183 has two VP6 core but they are sharing the IOVA.
> + * They could be used alone, or together. In order to avoid conflict,
> + * create an IOVA domain that could be shared by those two core.
> + * @iovad: The IOVA domain to share between the APU cores
> + * @refcount: Allow to automatically release the IOVA domain once all the APU
> + *            cores has been stopped
> + */
> +struct apu_iova_domain {
> +	struct iova_domain iovad;
> +	struct kref refcount;
> +};
> +
> +static dev_t rpmsg_major;
> +static DEFINE_IDA(rpmsg_ctrl_ida);
> +static DEFINE_IDA(rpmsg_minor_ida);
> +static DEFINE_IDA(req_ida);
> +static LIST_HEAD(requests);
> +static struct apu_iova_domain *apu_iovad;
> +
> +static int apu_rpmsg_callback(struct rpmsg_device *dev, void *data, int count,
> +			      void *priv, u32 addr)
> +{
> +	struct rpmsg_request *rpmsg_req;
> +	struct apu_dev_request *hdr = data;
> +
> +	list_for_each_entry(rpmsg_req, &requests, node) {
> +		struct apu_dev_request *tmp_hdr = rpmsg_req->req;
> +
> +		if (hdr->id == tmp_hdr->id) {
> +			memcpy(rpmsg_req->req, data, count);
> +			complete(&rpmsg_req->completion);
> +
> +			return 0;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int apu_device_memory_map(struct rpmsg_apu *apu,
> +				 struct apu_buffer *buffer)
> +{
> +	struct rpmsg_device *rpdev = apu->rpdev;
> +	phys_addr_t phys;
> +	int total_buf_space;
> +	int iova_pfn;
> +	int ret;
> +
> +	if (!buffer->fd)
> +		return 0;
> +
> +	buffer->dma_buf = dma_buf_get(buffer->fd);
> +	if (IS_ERR(buffer->dma_buf)) {
> +		dev_err(&rpdev->dev, "Failed to get dma_buf from fd: %ld\n",
> +			PTR_ERR(buffer->dma_buf));
> +		return PTR_ERR(buffer->dma_buf);
> +	}
> +
> +	buffer->attachment = dma_buf_attach(buffer->dma_buf, &rpdev->dev);
> +	if (IS_ERR(buffer->attachment)) {
> +		dev_err(&rpdev->dev, "Failed to attach dma_buf\n");
> +		ret = PTR_ERR(buffer->attachment);
> +		goto err_dma_buf_put;
> +	}
> +
> +	buffer->sg_table = dma_buf_map_attachment(buffer->attachment,
> +						   DMA_BIDIRECTIONAL);
> +	if (IS_ERR(buffer->sg_table)) {
> +		dev_err(&rpdev->dev, "Failed to map attachment\n");
> +		ret = PTR_ERR(buffer->sg_table);
> +		goto err_dma_buf_detach;
> +	}
> +	phys = page_to_phys(sg_page(buffer->sg_table->sgl));
> +	total_buf_space = sg_dma_len(buffer->sg_table->sgl);
> +
> +	iova_pfn = alloc_iova_fast(apu->iovad, total_buf_space >> PAGE_SHIFT,
> +				   apu->iova_limit_pfn, true);
> +	if (!iova_pfn) {
> +		dev_err(&rpdev->dev, "Failed to allocate iova address\n");
> +		ret = -ENOMEM;
> +		goto err_dma_unmap_attachment;
> +	}
> +
> +	buffer->iova = PFN_PHYS(iova_pfn);
> +	ret = iommu_map(apu->rproc->domain, buffer->iova, phys, total_buf_space,
> +			IOMMU_READ | IOMMU_WRITE | IOMMU_CACHE);
> +	if (ret) {
> +		dev_err(&rpdev->dev, "Failed to iommu map\n");
> +		goto err_free_iova;
> +	}
> +
> +	return 0;
> +
> +err_free_iova:
> +	free_iova(apu->iovad, iova_pfn);
> +err_dma_unmap_attachment:
> +	dma_buf_unmap_attachment(buffer->attachment,
> +				 buffer->sg_table,
> +				 DMA_BIDIRECTIONAL);
> +err_dma_buf_detach:
> +	dma_buf_detach(buffer->dma_buf, buffer->attachment);
> +err_dma_buf_put:
> +	dma_buf_put(buffer->dma_buf);
> +
> +	return ret;
> +}
> +
> +static void apu_device_memory_unmap(struct rpmsg_apu *apu,
> +				    struct apu_buffer *buffer)
> +{
> +	int total_buf_space;
> +
> +	if (!buffer->fd)
> +		return;
> +
> +	total_buf_space = sg_dma_len(buffer->sg_table->sgl);
> +	iommu_unmap(apu->rproc->domain, buffer->iova, total_buf_space);
> +	free_iova(apu->iovad, PHYS_PFN(buffer->iova));
> +	dma_buf_unmap_attachment(buffer->attachment,
> +				 buffer->sg_table,
> +				 DMA_BIDIRECTIONAL);
> +	dma_buf_detach(buffer->dma_buf, buffer->attachment);
> +	dma_buf_put(buffer->dma_buf);
> +}
> +
> +static int _apu_send_request(struct rpmsg_apu *apu,
> +			     struct rpmsg_device *rpdev,
> +			     struct apu_dev_request *req, int len)
> +{
> +
> +	struct rpmsg_request *rpmsg_req;
> +	int ret = 0;
> +
> +	req->id = ida_simple_get(&req_ida, 0, 0xffff, GFP_KERNEL);
> +	if (req->id < 0)
> +		return ret;
> +
> +	rpmsg_req = kzalloc(sizeof(*rpmsg_req), GFP_KERNEL);
> +	if (!rpmsg_req)
> +		return -ENOMEM;
> +
> +	rpmsg_req->req = req;
> +	init_completion(&rpmsg_req->completion);
> +	list_add(&rpmsg_req->node, &requests);
> +
> +	ret = rpmsg_send(rpdev->ept, req, len);
> +	if (ret)
> +		goto free_req;
> +
> +	/* be careful with race here between timeout and callback*/
> +	ret = wait_for_completion_timeout(&rpmsg_req->completion,
> +					  msecs_to_jiffies(1000));
> +	if (!ret)
> +		ret = -ETIMEDOUT;
> +	else
> +		ret = 0;
> +
> +	ida_simple_remove(&req_ida, req->id);
> +
> +free_req:
> +
> +	list_del(&rpmsg_req->node);
> +	kfree(rpmsg_req);
> +
> +	return ret;
> +}
> +
> +static int apu_send_request(struct rpmsg_apu *apu,
> +			    struct apu_request *req)
> +{
> +	int ret;
> +	struct rpmsg_device *rpdev = apu->rpdev;
> +	struct apu_dev_request *dev_req;
> +	struct apu_buffer *buffer;
> +
> +	int size = req->size_in + req->size_out +
> +		sizeof(u32) * req->count * 2 + sizeof(*dev_req);
> +	u32 *fd = (u32 *)(req->data + req->size_in + req->size_out);
> +	u32 *buffer_size = (u32 *)(fd + req->count);
> +	u32 *dev_req_da;
> +	u32 *dev_req_buffer_size;
> +	int i;
> +
> +	dev_req = kmalloc(size, GFP_KERNEL);
> +	if (!dev_req)
> +		return -ENOMEM;
> +
> +	dev_req->cmd = req->cmd;
> +	dev_req->size_in = req->size_in;
> +	dev_req->size_out = req->size_out;
> +	dev_req->count = req->count;
> +	dev_req_da = (u32 *)(dev_req->data + req->size_in + req->size_out);

I have started to review this set but it will take me more time to wrap my head
around what you are doing (the overall lack of comments in the code doesn't
help).

In the mean time the "dev_req->data" above is very puzzling to me - did you mean
to write "req-data"?  Otherwise I don't know how this can work since
dev_req->data is not initalised after the kmalloc(). 

More comments will come tomorrow.

Thanks,
Mathieu

> +	dev_req_buffer_size = (u32 *)(dev_req_da + dev_req->count);
> +	memcpy(dev_req->data, req->data, req->size_in);
> +
> +	buffer = kmalloc_array(req->count, sizeof(*buffer), GFP_KERNEL);
> +	for (i = 0; i < req->count; i++) {
> +		buffer[i].fd = fd[i];
> +		ret = apu_device_memory_map(apu, &buffer[i]);
> +		if (ret)
> +			goto err_free_memory;
> +		dev_req_da[i] = buffer[i].iova;
> +		dev_req_buffer_size[i] = buffer_size[i];
> +	}
> +
> +	ret = _apu_send_request(apu, rpdev, dev_req, size);
> +
> +err_free_memory:
> +	for (i--; i >= 0; i--)
> +		apu_device_memory_unmap(apu, &buffer[i]);
> +
> +	req->result = dev_req->result;
> +	req->size_in = dev_req->size_in;
> +	req->size_out = dev_req->size_out;
> +	memcpy(req->data, dev_req->data, dev_req->size_in + dev_req->size_out +
> +	       sizeof(u32) * req->count);
> +
> +	kfree(buffer);
> +	kfree(dev_req);
> +
> +	return ret;
> +}
> +
> +
> +static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
> +			       unsigned long arg)
> +{
> +	struct rpmsg_apu *apu = fp->private_data;
> +	struct apu_request apu_req;
> +	struct apu_request *apu_req_full;
> +	void __user *argp = (void __user *)arg;
> +	int len;
> +	int ret;
> +
> +	switch (cmd) {
> +	case APU_SEND_REQ_IOCTL:
> +		/* Get the header */
> +		if (copy_from_user(&apu_req, argp,
> +				   sizeof(apu_req)))
> +			return -EFAULT;
> +
> +		len = sizeof(*apu_req_full) + apu_req.size_in +
> +			apu_req.size_out + apu_req.count * sizeof(u32) * 2;
> +		apu_req_full = kzalloc(len, GFP_KERNEL);
> +		if (!apu_req_full)
> +			return -ENOMEM;
> +
> +		/* Get the whole request */
> +		if (copy_from_user(apu_req_full, argp, len)) {
> +			kfree(apu_req_full);
> +			return -EFAULT;
> +		}
> +
> +		ret = apu_send_request(apu, apu_req_full);
> +		if (ret) {
> +			kfree(apu_req_full);
> +			return ret;
> +		}
> +
> +		if (copy_to_user(argp, apu_req_full, sizeof(apu_req) +
> +				 sizeof(u32) * apu_req_full->count +
> +				 apu_req_full->size_in + apu_req_full->size_out))
> +			ret = -EFAULT;
> +
> +		kfree(apu_req_full);
> +		return ret;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
> +{
> +	struct rpmsg_apu *apu = cdev_to_apu(inode->i_cdev);
> +
> +	get_device(&apu->dev);
> +	filp->private_data = apu;
> +
> +	return 0;
> +}
> +
> +static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
> +{
> +	struct rpmsg_apu *apu = cdev_to_apu(inode->i_cdev);
> +
> +	put_device(&apu->dev);
> +
> +	return 0;
> +}
> +
> +static const struct file_operations rpmsg_eptdev_fops = {
> +	.owner = THIS_MODULE,
> +	.open = rpmsg_eptdev_open,
> +	.release = rpmsg_eptdev_release,
> +	.unlocked_ioctl = rpmsg_eptdev_ioctl,
> +	.compat_ioctl = rpmsg_eptdev_ioctl,
> +};
> +
> +static void iova_domain_release(struct kref *ref)
> +{
> +	put_iova_domain(&apu_iovad->iovad);
> +	kfree(apu_iovad);
> +	apu_iovad = NULL;
> +}
> +
> +static struct fw_rsc_iova *apu_find_rcs_iova(struct rpmsg_apu *apu)
> +{
> +	struct rproc *rproc = apu->rproc;
> +	struct resource_table *table;
> +	struct fw_rsc_iova *rsc;
> +	int i;
> +
> +	table = rproc->table_ptr;
> +	for (i = 0; i < table->num; i++) {
> +		int offset = table->offset[i];
> +		struct fw_rsc_hdr *hdr = (void *)table + offset;
> +
> +		switch (hdr->type) {
> +		case RSC_VENDOR_IOVA:
> +			rsc = (void *)hdr + sizeof(*hdr);
> +				return rsc;
> +			break;
> +		default:
> +			continue;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static int apu_reserve_iova(struct rpmsg_apu *apu, struct iova_domain *iovad)
> +{
> +	struct rproc *rproc = apu->rproc;
> +	struct resource_table *table;
> +	struct fw_rsc_carveout *rsc;
> +	int i;
> +
> +	table = rproc->table_ptr;
> +	for (i = 0; i < table->num; i++) {
> +		int offset = table->offset[i];
> +		struct fw_rsc_hdr *hdr = (void *)table + offset;
> +
> +		if (hdr->type == RSC_CARVEOUT) {
> +			struct iova *iova;
> +
> +			rsc = (void *)hdr + sizeof(*hdr);
> +			iova = reserve_iova(iovad, PHYS_PFN(rsc->da),
> +					    PHYS_PFN(rsc->da + rsc->len));
> +			if (!iova) {
> +				dev_err(&apu->dev, "failed to reserve iova\n");
> +				return -ENOMEM;
> +			}
> +			dev_dbg(&apu->dev, "Reserve: %x - %x\n",
> +				rsc->da, rsc->da + rsc->len);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int apu_init_iovad(struct rpmsg_apu *apu)
> +{
> +	struct fw_rsc_iova *rsc;
> +
> +	if (!apu->rproc->table_ptr) {
> +		dev_err(&apu->dev,
> +			"No resource_table: has the firmware been loaded ?\n");
> +		return -ENODEV;
> +	}
> +
> +	rsc = apu_find_rcs_iova(apu);
> +	if (!rsc) {
> +		dev_err(&apu->dev, "No iova range defined in resource_table\n");
> +		return -ENOMEM;
> +	}
> +
> +	if (!apu_iovad) {
> +		apu_iovad = kzalloc(sizeof(*apu_iovad), GFP_KERNEL);
> +		if (!apu_iovad)
> +			return -ENOMEM;
> +
> +		init_iova_domain(&apu_iovad->iovad, PAGE_SIZE,
> +				 PHYS_PFN(rsc->da));
> +		apu_reserve_iova(apu, &apu_iovad->iovad);
> +		kref_init(&apu_iovad->refcount);
> +	} else
> +		kref_get(&apu_iovad->refcount);
> +
> +	apu->iovad = &apu_iovad->iovad;
> +	apu->iova_limit_pfn = PHYS_PFN(rsc->da + rsc->len) - 1;
> +
> +	return 0;
> +}
> +
> +static struct rproc *apu_get_rproc(struct rpmsg_device *rpdev)
> +{
> +	/*
> +	 * To work, the APU RPMsg driver need to get the rproc device.
> +	 * Currently, we only use virtio so we could use that to find the
> +	 * remoteproc parent.
> +	 */
> +	if (!rpdev->dev.parent && rpdev->dev.parent->bus) {
> +		dev_err(&rpdev->dev, "invalid rpmsg device\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	if (strcmp(rpdev->dev.parent->bus->name, "virtio")) {
> +		dev_err(&rpdev->dev, "unsupported bus\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	return vdev_to_rproc(dev_to_virtio(rpdev->dev.parent));
> +}
> +
> +static void rpmsg_apu_release_device(struct device *dev)
> +{
> +	struct rpmsg_apu *apu = dev_to_apu(dev);
> +
> +	ida_simple_remove(&rpmsg_ctrl_ida, dev->id);
> +	ida_simple_remove(&rpmsg_minor_ida, MINOR(dev->devt));
> +	cdev_del(&apu->cdev);
> +	kfree(apu);
> +}
> +
> +static int apu_rpmsg_probe(struct rpmsg_device *rpdev)
> +{
> +	struct rpmsg_apu *apu;
> +	struct device *dev;
> +	int ret;
> +
> +	apu = devm_kzalloc(&rpdev->dev, sizeof(*apu), GFP_KERNEL);
> +	if (!apu)
> +		return -ENOMEM;
> +	apu->rpdev = rpdev;
> +
> +	apu->rproc = apu_get_rproc(rpdev);
> +	if (IS_ERR_OR_NULL(apu->rproc))
> +		return PTR_ERR(apu->rproc);
> +
> +	dev = &apu->dev;
> +	device_initialize(dev);
> +	dev->parent = &rpdev->dev;
> +
> +	cdev_init(&apu->cdev, &rpmsg_eptdev_fops);
> +	apu->cdev.owner = THIS_MODULE;
> +
> +	ret = ida_simple_get(&rpmsg_minor_ida, 0, APU_DEV_MAX, GFP_KERNEL);
> +	if (ret < 0)
> +		goto free_apu;
> +	dev->devt = MKDEV(MAJOR(rpmsg_major), ret);
> +
> +	ret = ida_simple_get(&rpmsg_ctrl_ida, 0, 0, GFP_KERNEL);
> +	if (ret < 0)
> +		goto free_minor_ida;
> +	dev->id = ret;
> +	dev_set_name(&apu->dev, "apu%d", ret);
> +
> +	ret = cdev_add(&apu->cdev, dev->devt, 1);
> +	if (ret)
> +		goto free_ctrl_ida;
> +
> +	/* We can now rely on the release function for cleanup */
> +	dev->release = rpmsg_apu_release_device;
> +
> +	ret = device_add(dev);
> +	if (ret) {
> +		dev_err(&rpdev->dev, "device_add failed: %d\n", ret);
> +		put_device(dev);
> +	}
> +
> +	/* Make device dma capable by inheriting from parent's capabilities */
> +	set_dma_ops(&rpdev->dev, get_dma_ops(apu->rproc->dev.parent));
> +
> +	ret = dma_coerce_mask_and_coherent(&rpdev->dev,
> +					   dma_get_mask(apu->rproc->dev.parent));
> +	if (ret)
> +		goto err_put_device;
> +
> +	rpdev->dev.iommu_group = apu->rproc->dev.parent->iommu_group;
> +
> +	ret = apu_init_iovad(apu);
> +
> +	dev_set_drvdata(&rpdev->dev, apu);
> +
> +	return ret;
> +
> +err_put_device:
> +	put_device(dev);
> +free_ctrl_ida:
> +	ida_simple_remove(&rpmsg_ctrl_ida, dev->id);
> +free_minor_ida:
> +	ida_simple_remove(&rpmsg_minor_ida, MINOR(dev->devt));
> +free_apu:
> +	put_device(dev);
> +	kfree(apu);
> +
> +	return ret;
> +}
> +
> +static void apu_rpmsg_remove(struct rpmsg_device *rpdev)
> +{
> +	struct rpmsg_apu *apu = dev_get_drvdata(&rpdev->dev);
> +
> +	if (apu_iovad)
> +		kref_put(&apu_iovad->refcount, iova_domain_release);
> +
> +	device_del(&apu->dev);
> +	put_device(&apu->dev);
> +	kfree(apu);
> +}
> +
> +static const struct rpmsg_device_id apu_rpmsg_match[] = {
> +	{ APU_RPMSG_SERVICE_MT8183 },
> +	{}
> +};
> +
> +static struct rpmsg_driver apu_rpmsg_driver = {
> +	.probe = apu_rpmsg_probe,
> +	.remove = apu_rpmsg_remove,
> +	.callback = apu_rpmsg_callback,
> +	.id_table = apu_rpmsg_match,
> +	.drv  = {
> +		.name  = "apu_rpmsg",
> +	},
> +};
> +
> +static int __init apu_rpmsg_init(void)
> +{
> +	int ret;
> +
> +	ret = alloc_chrdev_region(&rpmsg_major, 0, APU_DEV_MAX, "apu");
> +	if (ret < 0) {
> +		pr_err("apu: failed to allocate char dev region\n");
> +		return ret;
> +	}
> +
> +	return register_rpmsg_driver(&apu_rpmsg_driver);
> +}
> +arch_initcall(apu_rpmsg_init);
> +
> +static void __exit apu_rpmsg_exit(void)
> +{
> +	unregister_rpmsg_driver(&apu_rpmsg_driver);
> +}
> +module_exit(apu_rpmsg_exit);
> +
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("APU RPMSG driver");
> diff --git a/drivers/rpmsg/apu_rpmsg.h b/drivers/rpmsg/apu_rpmsg.h
> new file mode 100644
> index 000000000000..54b5b7880750
> --- /dev/null
> +++ b/drivers/rpmsg/apu_rpmsg.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * Copyright 2020 BayLibre SAS
> + */
> +
> +#ifndef __APU_RPMSG_H__
> +#define __APU_RPMSG_H__
> +
> +/*
> + * Firmware request, must be aligned with the one defined in firmware.
> + * @id: Request id, used in the case of reply, to find the pending request
> + * @cmd: The command id to execute in the firmware
> + * @result: The result of the command executed on the firmware
> + * @size: The size of the data available in this request
> + * @count: The number of shared buffer
> + * @data: Contains the data attached with the request if size is greater than
> + *        zero, and the addresses of shared buffers if count is greater than
> + *        zero. Both the data and the shared buffer could be read and write
> + *        by the APU.
> + */
> +struct  apu_dev_request {
> +	u16 id;
> +	u16 cmd;
> +	u16 result;
> +	u16 size_in;
> +	u16 size_out;
> +	u16 count;
> +	u8 data[0];
> +} __packed;
> +
> +#define APU_RPMSG_SERVICE_MT8183 "rpmsg-mt8183-apu0"
> +#define APU_CTRL_SRC 1
> +#define APU_CTRL_DST 1
> +
> +/* Vendor specific resource table entry */
> +#define RSC_VENDOR_IOVA 128
> +
> +/*
> + * Firmware IOVA resource table entry
> + * Define a range of virtual device address that could mapped using the IOMMU.
> + * @da: Start virtual device address
> + * @len: Length of the virtual device address
> + * @name: name of the resource
> + */
> +struct fw_rsc_iova {
> +	u32 da;
> +	u32 len;
> +	u32 reserved;
> +	u8 name[32];
> +} __packed;
> +
> +#endif /* __APU_RPMSG_H__ */
> diff --git a/include/uapi/linux/apu_rpmsg.h b/include/uapi/linux/apu_rpmsg.h
> new file mode 100644
> index 000000000000..81c9e4af9a94
> --- /dev/null
> +++ b/include/uapi/linux/apu_rpmsg.h
> @@ -0,0 +1,36 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * Copyright (c) 2020 BayLibre
> + */
> +
> +#ifndef _UAPI_RPMSG_APU_H_
> +#define _UAPI_RPMSG_APU_H_
> +
> +#include <linux/ioctl.h>
> +#include <linux/types.h>
> +
> +/*
> + * Structure containing the APU request from userspace application
> + * @cmd: The id of the command to execute on the APU
> + * @result: The result of the command executed on the APU
> + * @size: The size of the data available in this request
> + * @count: The number of shared buffer
> + * @data: Contains the data attached with the request if size is greater than
> + *        zero, and the files descriptors of shared buffers if count is greater
> + *        than zero. Both the data and the shared buffer could be read and write
> + *        by the APU.
> + */
> +struct apu_request {
> +	__u16 cmd;
> +	__u16 result;
> +	__u16 size_in;
> +	__u16 size_out;
> +	__u16 count;
> +	__u16 reserved;
> +	__u8 data[0];
> +};
> +
> +/* Send synchronous request to an APU */
> +#define APU_SEND_REQ_IOCTL	_IOWR(0xb7, 0x2, struct apu_request)
> +
> +#endif
> -- 
> 2.26.2
>