remoteproc_core.c

/*
 * Remote Processor Framework
 *
 * Copyright (C) 2011 Texas Instruments, Inc.
 * Copyright (C) 2011 Google, Inc.
 *
 * Ohad Ben-Cohen <ohad@wizery.com>
 * Brian Swetland <swetland@google.com>
 * Mark Grosen <mgrosen@ti.com>
 * Fernando Guzman Lugo <fernando.lugo@ti.com>
 * Suman Anna <s-anna@ti.com>
 * Robert Tivy <rtivy@ti.com>
 * Armando Uribe De Leon <x0095078@ti.com>
 *
 * 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.
 */

#define pr_fmt(fmt)    "%s: " fmt, __func__

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/dma-mapping.h>
#include <linux/firmware.h>
#include <linux/string.h>
#include <linux/debugfs.h>
#include <linux/remoteproc.h>
#include <linux/iommu.h>
#include <linux/klist.h>
#include <linux/elf.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_ring.h>

#include "remoteproc_internal.h"

static void klist_rproc_get(struct klist_node *n);
static void klist_rproc_put(struct klist_node *n);

/*
 * klist of the available remote processors.
 *
 * We need this in order to support name-based lookups (needed by the
 * rproc_get_by_name()).
 *
 * That said, we don't use rproc_get_by_name() anymore within the rpmsg
 * framework. The use cases that do require its existence should be
 * scrutinized, and hopefully migrated to rproc_boot() using device-based
 * binding.
 *
 * If/when this materializes, we could drop the klist (and the by_name
 * API).
 */
static DEFINE_KLIST(rprocs, klist_rproc_get, klist_rproc_put);

typedef int (*rproc_handle_resources_t)(struct rproc *rproc,
				struct fw_resource *rsc, int len);

/*
 * This is the IOMMU fault handler we register with the IOMMU API
 * (when relevant; not all remote processors access memory through
 * an IOMMU).
 *
 * IOMMU core will invoke this handler whenever the remote processor
 * will try to access an unmapped device address.
 *
 * Currently this is mostly a stub, but it will be later used to trigger
 * the recovery of the remote processor.
 */
static int rproc_iommu_fault(struct iommu_domain *domain, struct device *dev,
		unsigned long iova, int flags)
{
	dev_err(dev, "iommu fault: da 0x%lx flags 0x%x\n", iova, flags);

	/*
	 * Let the iommu core know we're not really handling this fault;
	 * we just plan to use this as a recovery trigger.
	 */
	return -ENOSYS;
}

static int rproc_enable_iommu(struct rproc *rproc)
{
	struct iommu_domain *domain;
	struct device *dev = rproc->dev;
	int ret;

	/*
	 * We currently use iommu_present() to decide if an IOMMU
	 * setup is needed.
	 *
	 * This works for simple cases, but will easily fail with
	 * platforms that do have an IOMMU, but not for this specific
	 * rproc.
	 *
	 * This will be easily solved by introducing hw capabilities
	 * that will be set by the remoteproc driver.
	 */
	if (!iommu_present(dev->bus)) {
		dev_dbg(dev, "iommu not found\n");
		return 0;
	}

	domain = iommu_domain_alloc(dev->bus);
	if (!domain) {
		dev_err(dev, "can't alloc iommu domain\n");
		return -ENOMEM;
	}

	iommu_set_fault_handler(domain, rproc_iommu_fault);

	ret = iommu_attach_device(domain, dev);
	if (ret) {
		dev_err(dev, "can't attach iommu device: %d\n", ret);
		goto free_domain;
	}

	rproc->domain = domain;

	return 0;

free_domain:
	iommu_domain_free(domain);
	return ret;
}

static void rproc_disable_iommu(struct rproc *rproc)
{
	struct iommu_domain *domain = rproc->domain;
	struct device *dev = rproc->dev;

	if (!domain)
		return;

	iommu_detach_device(domain, dev);
	iommu_domain_free(domain);

	return;
}

/*
 * Some remote processors will ask us to allocate them physically contiguous
 * memory regions (which we call "carveouts"), and map them to specific
 * device addresses (which are hardcoded in the firmware).
 *
 * They may then ask us to copy objects into specific device addresses (e.g.
 * code/data sections) or expose us certain symbols in other device address
 * (e.g. their trace buffer).
 *
 * This function is an internal helper with which we can go over the allocated
 * carveouts and translate specific device address to kernel virtual addresses
 * so we can access the referenced memory.
 *
 * Note: phys_to_virt(iommu_iova_to_phys(rproc->domain, da)) will work too,
 * but only on kernel direct mapped RAM memory. Instead, we're just using
 * here the output of the DMA API, which should be more correct.
 */
static void *rproc_da_to_va(struct rproc *rproc, u64 da, int len)
{
	struct rproc_mem_entry *carveout;
	void *ptr = NULL;

	list_for_each_entry(carveout, &rproc->carveouts, node) {
		int offset = da - carveout->da;

		/* try next carveout if da is too small */
		if (offset < 0)
			continue;

		/* try next carveout if da is too large */
		if (offset + len > carveout->len)
			continue;

		ptr = carveout->va + offset;

		break;
	}

	return ptr;
}

/**
 * rproc_load_segments() - load firmware segments to memory
 * @rproc: remote processor which will be booted using these fw segments
 * @elf_data: the content of the ELF firmware image
 *
 * This function loads the firmware segments to memory, where the remote
 * processor expects them.
 *
 * Some remote processors will expect their code and data to be placed
 * in specific device addresses, and can't have them dynamically assigned.
 *
 * We currently support only those kind of remote processors, and expect
 * the program header's paddr member to contain those addresses. We then go
 * through the physically contiguous "carveout" memory regions which we
 * allocated (and mapped) earlier on behalf of the remote processor,
 * and "translate" device address to kernel addresses, so we can copy the
 * segments where they are expected.
 *
 * Currently we only support remote processors that required carveout
 * allocations and got them mapped onto their iommus. Some processors
 * might be different: they might not have iommus, and would prefer to
 * directly allocate memory for every segment/resource. This is not yet
 * supported, though.
 */
static int rproc_load_segments(struct rproc *rproc, const u8 *elf_data)
{
	struct device *dev = rproc->dev;
	struct elf32_hdr *ehdr;
	struct elf32_phdr *phdr;
	int i, ret = 0;

	ehdr = (struct elf32_hdr *)elf_data;
	phdr = (struct elf32_phdr *)(elf_data + ehdr->e_phoff);

	/* go through the available ELF segments */
	for (i = 0; i < ehdr->e_phnum; i++, phdr++) {
		u32 da = phdr->p_paddr;
		u32 memsz = phdr->p_memsz;
		u32 filesz = phdr->p_filesz;
		void *ptr;

		if (phdr->p_type != PT_LOAD)
			continue;

		dev_dbg(dev, "phdr: type %d da 0x%x memsz 0x%x filesz 0x%x\n",
					phdr->p_type, da, memsz, filesz);

		if (filesz > memsz) {
			dev_err(dev, "bad phdr filesz 0x%x memsz 0x%x\n",
							filesz, memsz);
			ret = -EINVAL;
			break;
		}

		/* grab the kernel address for this device address */
		ptr = rproc_da_to_va(rproc, da, memsz);
		if (!ptr) {
			dev_err(dev, "bad phdr da 0x%x mem 0x%x\n", da, memsz);
			ret = -EINVAL;
			break;
		}

		/* put the segment where the remote processor expects it */
		if (phdr->p_filesz)
			memcpy(ptr, elf_data + phdr->p_offset, filesz);

		/*
		 * Zero out remaining memory for this segment.
		 *
		 * This isn't strictly required since dma_alloc_coherent already
		 * did this for us. albeit harmless, we may consider removing
		 * this.
		 */
		if (memsz > filesz)
			memset(ptr + filesz, 0, memsz - filesz);
	}

	return ret;
}

/**
 * rproc_handle_virtio_hdr() - handle a virtio header resource
 * @rproc: the remote processor
 * @rsc: the resource descriptor
 *
 * The existence of this virtio hdr resource entry means that the firmware
 * of this @rproc supports this virtio device.
 *
 * Currently we support only a single virtio device of type VIRTIO_ID_RPMSG,
 * but the plan is to remove this limitation and support any number
 * of virtio devices (and of any type). We'll also add support for dynamically
 * adding (and removing) virtio devices over the rpmsg bus, but small
 * firmwares that doesn't want to get involved with rpmsg will be able
 * to simple use the resource table for this.
 *
 * At this point this virtio header entry is rather simple: it just
 * announces the virtio device id and the supported virtio device features.
 * The plan though is to extend this to include the vring information and
 * the virtio config space, too (but first, some resource table overhaul
 * is needed: move from fixed-sized to variable-length TLV entries).
 *
 * For now, the 'flags' member of the resource entry contains the virtio
 * device id, the 'da' member contains the device features, and 'pa' is
 * where we need to store the guest features once negotiation completes.
 * As usual, the 'id' member of this resource contains the index of this
 * resource type (i.e. is this the first virtio hdr entry, the 2nd, ...).
 *
 * Returns 0 on success, or an appropriate error code otherwise
 */
static int rproc_handle_virtio_hdr(struct rproc *rproc, struct fw_resource *rsc)
{
	struct rproc_vdev *rvdev;

	/* we only support VIRTIO_ID_RPMSG devices for now */
	if (rsc->flags != VIRTIO_ID_RPMSG) {
		dev_warn(rproc->dev, "unsupported vdev: %d\n", rsc->flags);
		return -EINVAL;
	}

	/* we only support a single vdev per rproc for now */
	if (rsc->id || rproc->rvdev) {
		dev_warn(rproc->dev, "redundant vdev entry: %s\n", rsc->name);
		return -EINVAL;
	}

	rvdev = kzalloc(sizeof(struct rproc_vdev), GFP_KERNEL);
	if (!rvdev)
		return -ENOMEM;

	/* remember the device features */
	rvdev->dfeatures = rsc->da;

	rproc->rvdev = rvdev;
	rvdev->rproc = rproc;

	return 0;
}

/**
 * rproc_handle_vring() - handle a vring fw resource
 * @rproc: the remote processor
 * @rsc: the vring resource descriptor
 *
 * This resource entry requires allocation of non-cacheable memory
 * for a virtio vring. Currently we only support two vrings per remote
 * processor, required for the virtio rpmsg device.
 *
 * The 'len' member of @rsc should contain the number of buffers this vring
 * support and 'da' should either contain the device address where
 * the remote processor is expecting the vring, or indicate that
 * dynamically allocation of the vring's device address is supported.
 *
 * Note: 'da' is currently not handled. This will be revised when the generic
 * iommu-based DMA API will arrive, or a dynanic & non-iommu use case show
 * up. Meanwhile, statically-addressed iommu-based images should use
 * RSC_DEVMEM resource entries to map their require 'da' to the physical
 * address of their base CMA region.
 *
 * Returns 0 on success, or an appropriate error code otherwise
 */
static int rproc_handle_vring(struct rproc *rproc, struct fw_resource *rsc)
{
	struct device *dev = rproc->dev;
	struct rproc_vdev *rvdev = rproc->rvdev;
	dma_addr_t dma;
	int size, id = rsc->id;
	void *va;

	/* no vdev is in place ? */
	if (!rvdev) {
		dev_err(dev, "vring requested without a virtio dev entry\n");
		return -EINVAL;
	}

	/* the firmware must provide the expected queue size */
	if (!rsc->len) {
		dev_err(dev, "missing expected queue size\n");
		return -EINVAL;
	}

	/* we currently support two vrings per rproc (for rx and tx) */
	if (id >= ARRAY_SIZE(rvdev->vring)) {
		dev_err(dev, "%s: invalid vring id %d\n", rsc->name, id);
		return -EINVAL;
	}

	/* have we already allocated this vring id ? */
	if (rvdev->vring[id].len) {
		dev_err(dev, "%s: duplicated id %d\n", rsc->name, id);
		return -EINVAL;
	}

	/* actual size of vring (in bytes) */
	size = PAGE_ALIGN(vring_size(rsc->len, AMP_VRING_ALIGN));

	/*
	 * Allocate non-cacheable memory for the vring. In the future
	 * this call will also configure the IOMMU for us
	 */
	va = dma_alloc_coherent(dev, size, &dma, GFP_KERNEL);
	if (!va) {
		dev_err(dev, "dma_alloc_coherent failed\n");
		return -ENOMEM;
	}

	dev_dbg(dev, "vring%d: va %p dma %x qsz %d ring size %x\n", id, va,
					dma, rsc->len, size);

	rvdev->vring[id].len = rsc->len;
	rvdev->vring[id].va = va;
	rvdev->vring[id].dma = dma;

	return 0;
}

/**
 * rproc_handle_trace() - handle a shared trace buffer resource
 * @rproc: the remote processor
 * @rsc: the trace resource descriptor
 *
 * In case the remote processor dumps trace logs into memory,
 * export it via debugfs.
 *
 * Currently, the 'da' member of @rsc should contain the device address
 * where the remote processor is dumping the traces. Later we could also
 * support dynamically allocating this address using the generic
 * DMA API (but currently there isn't a use case for that).
 *
 * Returns 0 on success, or an appropriate error code otherwise
 */
static int rproc_handle_trace(struct rproc *rproc, struct fw_resource *rsc)
{
	struct rproc_mem_entry *trace;
	struct device *dev = rproc->dev;
	void *ptr;
	char name[15];

	/* what's the kernel address of this resource ? */
	ptr = rproc_da_to_va(rproc, rsc->da, rsc->len);
	if (!ptr) {
		dev_err(dev, "erroneous trace resource entry\n");
		return -EINVAL;
	}

	trace = kzalloc(sizeof(*trace), GFP_KERNEL);
	if (!trace) {
		dev_err(dev, "kzalloc trace failed\n");
		return -ENOMEM;
	}

	/* set the trace buffer dma properties */
	trace->len = rsc->len;
	trace->va = ptr;

	/* make sure snprintf always null terminates, even if truncating */
	snprintf(name, sizeof(name), "trace%d", rproc->num_traces);

	/* create the debugfs entry */
	trace->priv = rproc_create_trace_file(name, rproc, trace);
	if (!trace->priv) {
		trace->va = NULL;
		kfree(trace);
		return -EINVAL;
	}

	list_add_tail(&trace->node, &rproc->traces);

	rproc->num_traces++;

	dev_dbg(dev, "%s added: va %p, da 0x%llx, len 0x%x\n", name, ptr,
						rsc->da, rsc->len);

	return 0;
}

/**
 * rproc_handle_devmem() - handle devmem resource entry
 * @rproc: remote processor handle
 * @rsc: the devmem resource entry
 *
 * Remote processors commonly need to access certain on-chip peripherals.
 *
 * Some of these remote processors access memory via an iommu device,
 * and might require us to configure their iommu before they can access
 * the on-chip peripherals they need.
 *
 * This resource entry is a request to map such a peripheral device.
 *
 * These devmem entries will contain the physical address of the device in
 * the 'pa' member. If a specific device address is expected, then 'da' will
 * contain it (currently this is the only use case supported). 'len' will
 * contain the size of the physical region we need to map.
 *
 * Currently we just "trust" those devmem entries to contain valid physical
 * addresses, but this is going to change: we want the implementations to
 * tell us ranges of physical addresses the firmware is allowed to request,
 * and not allow firmwares to request access to physical addresses that
 * are outside those ranges.
 */
static int rproc_handle_devmem(struct rproc *rproc, struct fw_resource *rsc)
{
	struct rproc_mem_entry *mapping;
	int ret;

	/* no point in handling this resource without a valid iommu domain */
	if (!rproc->domain)
		return -EINVAL;

	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
	if (!mapping) {
		dev_err(rproc->dev, "kzalloc mapping failed\n");
		return -ENOMEM;
	}

	ret = iommu_map(rproc->domain, rsc->da, rsc->pa, rsc->len, rsc->flags);
	if (ret) {
		dev_err(rproc->dev, "failed to map devmem: %d\n", ret);
		goto out;
	}

	/*
	 * We'll need this info later when we'll want to unmap everything
	 * (e.g. on shutdown).
	 *
	 * We can't trust the remote processor not to change the resource
	 * table, so we must maintain this info independently.
	 */
	mapping->da = rsc->da;
	mapping->len = rsc->len;
	list_add_tail(&mapping->node, &rproc->mappings);

	dev_dbg(rproc->dev, "mapped devmem pa 0x%llx, da 0x%llx, len 0x%x\n",
					rsc->pa, rsc->da, rsc->len);

	return 0;

out:
	kfree(mapping);
	return ret;
}

/**
 * rproc_handle_carveout() - handle phys contig memory allocation requests
 * @rproc: rproc handle
 * @rsc: the resource entry
 *
 * This function will handle firmware requests for allocation of physically
 * contiguous memory regions.
 *
 * These request entries should come first in the firmware's resource table,
 * as other firmware entries might request placing other data objects inside
 * these memory regions (e.g. data/code segments, trace resource entries, ...).
 *
 * Allocating memory this way helps utilizing the reserved physical memory
 * (e.g. CMA) more efficiently, and also minimizes the number of TLB entries
 * needed to map it (in case @rproc is using an IOMMU). Reducing the TLB
 * pressure is important; it may have a substantial impact on performance.
 */
static int rproc_handle_carveout(struct rproc *rproc, struct fw_resource *rsc)
{
	struct rproc_mem_entry *carveout, *mapping;
	struct device *dev = rproc->dev;
	dma_addr_t dma;
	void *va;
	int ret;

	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
	if (!mapping) {
		dev_err(dev, "kzalloc mapping failed\n");
		return -ENOMEM;
	}

	carveout = kzalloc(sizeof(*carveout), GFP_KERNEL);
	if (!carveout) {
		dev_err(dev, "kzalloc carveout failed\n");
		ret = -ENOMEM;
		goto free_mapping;
	}

	va = dma_alloc_coherent(dev, rsc->len, &dma, GFP_KERNEL);
	if (!va) {
		dev_err(dev, "failed to dma alloc carveout: %d\n", rsc->len);
		ret = -ENOMEM;
		goto free_carv;
	}

	dev_dbg(dev, "carveout va %p, dma %x, len 0x%x\n", va, dma, rsc->len);

	/*
	 * Ok, this is non-standard.
	 *
	 * Sometimes we can't rely on the generic iommu-based DMA API
	 * to dynamically allocate the device address and then set the IOMMU
	 * tables accordingly, because some remote processors might
	 * _require_ us to use hard coded device addresses that their
	 * firmware was compiled with.
	 *
	 * In this case, we must use the IOMMU API directly and map
	 * the memory to the device address as expected by the remote
	 * processor.
	 *
	 * Obviously such remote processor devices should not be configured
	 * to use the iommu-based DMA API: we expect 'dma' to contain the
	 * physical address in this case.
	 */
	if (rproc->domain) {
		ret = iommu_map(rproc->domain, rsc->da, dma, rsc->len,
								rsc->flags);
		if (ret) {
			dev_err(dev, "iommu_map failed: %d\n", ret);
			goto dma_free;
		}

		/*
		 * We'll need this info later when we'll want to unmap
		 * everything (e.g. on shutdown).
		 *
		 * We can't trust the remote processor not to change the
		 * resource table, so we must maintain this info independently.
		 */
		mapping->da = rsc->da;
		mapping->len = rsc->len;
		list_add_tail(&mapping->node, &rproc->mappings);

		dev_dbg(dev, "carveout mapped 0x%llx to 0x%x\n", rsc->da, dma);

		/*
		 * Some remote processors might need to know the pa
		 * even though they are behind an IOMMU. E.g., OMAP4's
		 * remote M3 processor needs this so it can control
		 * on-chip hardware accelerators that are not behind
		 * the IOMMU, and therefor must know the pa.
		 *
		 * Generally we don't want to expose physical addresses
		 * if we don't have to (remote processors are generally
		 * _not_ trusted), so we might want to do this only for
		 * remote processor that _must_ have this (e.g. OMAP4's
		 * dual M3 subsystem).
		 */
		rsc->pa = dma;
	}

	carveout->va = va;
	carveout->len = rsc->len;
	carveout->dma = dma;
	carveout->da = rsc->da;

	list_add_tail(&carveout->node, &rproc->carveouts);

	return 0;

dma_free:
	dma_free_coherent(dev, rsc->len, va, dma);
free_carv:
	kfree(carveout);
free_mapping:
	kfree(mapping);
	return ret;
}

/* handle firmware resource entries before booting the remote processor */
static int
rproc_handle_boot_rsc(struct rproc *rproc, struct fw_resource *rsc, int len)
{
	struct device *dev = rproc->dev;
	int ret = 0;

	while (len >= sizeof(*rsc)) {
		dev_dbg(dev, "rsc: type %d, da 0x%llx, pa 0x%llx, len 0x%x, "
			"id %d, name %s, flags %x\n", rsc->type, rsc->da,
			rsc->pa, rsc->len, rsc->id, rsc->name, rsc->flags);

		switch (rsc->type) {
		case RSC_CARVEOUT:
			ret = rproc_handle_carveout(rproc, rsc);
			break;
		case RSC_DEVMEM:
			ret = rproc_handle_devmem(rproc, rsc);
			break;
		case RSC_TRACE:
			ret = rproc_handle_trace(rproc, rsc);
			break;
		case RSC_VRING:
			ret = rproc_handle_vring(rproc, rsc);
			break;
		case RSC_VIRTIO_DEV:
			/* this one is handled early upon registration */
			break;
		default:
			dev_warn(dev, "unsupported resource %d\n", rsc->type);
			break;
		}

		if (ret)
			break;

		rsc++;
		len -= sizeof(*rsc);
	}

	return ret;
}

/* handle firmware resource entries while registering the remote processor */
static int
rproc_handle_virtio_rsc(struct rproc *rproc, struct fw_resource *rsc, int len)
{
	struct device *dev = rproc->dev;
	int ret = -ENODEV;

	for (; len >= sizeof(*rsc); rsc++, len -= sizeof(*rsc))
		if (rsc->type == RSC_VIRTIO_DEV) {
			dev_dbg(dev, "found vdev %d/%s features %llx\n",
					rsc->flags, rsc->name, rsc->da);
			ret = rproc_handle_virtio_hdr(rproc, rsc);
			break;
		}

	return ret;
}

/**
 * rproc_handle_resources() - find and handle the resource table
 * @rproc: the rproc handle
 * @elf_data: the content of the ELF firmware image
 * @handler: function that should be used to handle the resource table
 *
 * This function finds the resource table inside the remote processor's
 * firmware, and invoke a user-supplied handler with it (we have two
 * possible handlers: one is invoked upon registration of @rproc,
 * in order to register the supported virito devices, and the other is
 * invoked when @rproc is actually booted).
 *
 * Currently this function fails if a resource table doesn't exist.
 * This restriction will be removed when we'll start supporting remote
 * processors that don't need a resource table.
 */
static int rproc_handle_resources(struct rproc *rproc, const u8 *elf_data,
					rproc_handle_resources_t handler)

{
	struct elf32_hdr *ehdr;
	struct elf32_shdr *shdr;
	const char *name_table;
	int i, ret = -EINVAL;

	ehdr = (struct elf32_hdr *)elf_data;
	shdr = (struct elf32_shdr *)(elf_data + ehdr->e_shoff);
	name_table = elf_data + shdr[ehdr->e_shstrndx].sh_offset;

	/* look for the resource table and handle it */
	for (i = 0; i < ehdr->e_shnum; i++, shdr++) {
		if (!strcmp(name_table + shdr->sh_name, ".resource_table")) {
			struct fw_resource *table = (struct fw_resource *)
						(elf_data + shdr->sh_offset);

			ret = handler(rproc, table, shdr->sh_size);

			break;
		}
	}

	return ret;
}

/**
 * rproc_resource_cleanup() - clean up and free all acquired resources
 * @rproc: rproc handle
 *
 * This function will free all resources acquired for @rproc, and it
 * is called when @rproc shuts down, or just failed booting.
 */
static void rproc_resource_cleanup(struct rproc *rproc)
{
	struct rproc_mem_entry *entry, *tmp;
	struct device *dev = rproc->dev;
	struct rproc_vdev *rvdev = rproc->rvdev;
	int i;

	/* clean up debugfs trace entries */
	list_for_each_entry_safe(entry, tmp, &rproc->traces, node) {
		rproc_remove_trace_file(entry->priv);
		rproc->num_traces--;
		list_del(&entry->node);
		kfree(entry);
	}

	/* free the coherent memory allocated for the vrings */
	for (i = 0; rvdev && i < ARRAY_SIZE(rvdev->vring); i++) {
		int qsz = rvdev->vring[i].len;
		void *va = rvdev->vring[i].va;
		int dma = rvdev->vring[i].dma;

		/* virtqueue size is expressed in number of buffers supported */
		if (qsz) {
			/* how many bytes does this vring really occupy ? */
			int size = PAGE_ALIGN(vring_size(qsz, AMP_VRING_ALIGN));

			dma_free_coherent(rproc->dev, size, va, dma);

			rvdev->vring[i].len = 0;
		}
	}

	/* clean up carveout allocations */
	list_for_each_entry_safe(entry, tmp, &rproc->carveouts, node) {
		dma_free_coherent(dev, entry->len, entry->va, entry->dma);
		list_del(&entry->node);
		kfree(entry);
	}

	/* clean up iommu mapping entries */
	list_for_each_entry_safe(entry, tmp, &rproc->mappings, node) {
		size_t unmapped;

		unmapped = iommu_unmap(rproc->domain, entry->da, entry->len);
		if (unmapped != entry->len) {
			/* nothing much to do besides complaining */
			dev_err(dev, "failed to unmap %u/%u\n", entry->len,
								unmapped);
		}

		list_del(&entry->node);
		kfree(entry);
	}
}

/* make sure this fw image is sane */
static int rproc_fw_sanity_check(struct rproc *rproc, const struct firmware *fw)
{
	const char *name = rproc->firmware;
	struct device *dev = rproc->dev;
	struct elf32_hdr *ehdr;

	if (!fw) {
		dev_err(dev, "failed to load %s\n", name);
		return -EINVAL;
	}

	if (fw->size < sizeof(struct elf32_hdr)) {
		dev_err(dev, "Image is too small\n");
		return -EINVAL;
	}

	ehdr = (struct elf32_hdr *)fw->data;

	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG)) {
		dev_err(dev, "Image is corrupted (bad magic)\n");
		return -EINVAL;
	}

	if (ehdr->e_phnum == 0) {
		dev_err(dev, "No loadable segments\n");
		return -EINVAL;
	}

	if (ehdr->e_phoff > fw->size) {
		dev_err(dev, "Firmware size is too small\n");
		return -EINVAL;
	}

	return 0;
}

/*
 * take a firmware and boot a remote processor with it.
 */
static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
{
	struct device *dev = rproc->dev;
	const char *name = rproc->firmware;
	struct elf32_hdr *ehdr;
	int ret;

	ret = rproc_fw_sanity_check(rproc, fw);
	if (ret)
		return ret;

	ehdr = (struct elf32_hdr *)fw->data;

	dev_info(dev, "Booting fw image %s, size %d\n", name, fw->size);

	/*
	 * if enabling an IOMMU isn't relevant for this rproc, this is
	 * just a nop
	 */
	ret = rproc_enable_iommu(rproc);
	if (ret) {
		dev_err(dev, "can't enable iommu: %d\n", ret);
		return ret;
	}

	/*
	 * The ELF entry point is the rproc's boot addr (though this is not
	 * a configurable property of all remote processors: some will always
	 * boot at a specific hardcoded address).
	 */
	rproc->bootaddr = ehdr->e_entry;

	/* handle fw resources which are required to boot rproc */
	ret = rproc_handle_resources(rproc, fw->data, rproc_handle_boot_rsc);
	if (ret) {
		dev_err(dev, "Failed to process resources: %d\n", ret);
		goto clean_up;
	}

	/* load the ELF segments to memory */
	ret = rproc_load_segments(rproc, fw->data);
	if (ret) {
		dev_err(dev, "Failed to load program segments: %d\n", ret);
		goto clean_up;
	}

	/* power up the remote processor */
	ret = rproc->ops->start(rproc);
	if (ret) {
		dev_err(dev, "can't start rproc %s: %d\n", rproc->name, ret);
		goto clean_up;
	}

	rproc->state = RPROC_RUNNING;

	dev_info(dev, "remote processor %s is now up\n", rproc->name);

	return 0;

clean_up:
	rproc_resource_cleanup(rproc);
	rproc_disable_iommu(rproc);
	return ret;
}

/*
 * take a firmware and look for virtio devices to register.
 *
 * Note: this function is called asynchronously upon registration of the
 * remote processor (so we must wait until it completes before we try
 * to unregister the device. one other option is just to use kref here,
 * that might be cleaner).
 */
static void rproc_fw_config_virtio(const struct firmware *fw, void *context)
{
	struct rproc *rproc = context;
	struct device *dev = rproc->dev;
	int ret;

	if (rproc_fw_sanity_check(rproc, fw) < 0)
		goto out;

	/* does the fw supports any virtio devices ? */
	ret = rproc_handle_resources(rproc, fw->data, rproc_handle_virtio_rsc);
	if (ret) {
		dev_info(dev, "No fw virtio device was found\n");
		goto out;
	}

	/* add the virtio device (currently only rpmsg vdevs are supported) */
	ret = rproc_add_rpmsg_vdev(rproc);
	if (ret)
		goto out;

out:
	if (fw)
		release_firmware(fw);
	/* allow rproc_unregister() contexts, if any, to proceed */
	complete_all(&rproc->firmware_loading_complete);
}

/**
 * rproc_boot() - boot a remote processor
 * @rproc: handle of a remote processor
 *
 * Boot a remote processor (i.e. load its firmware, power it on, ...).
 *
 * If the remote processor is already powered on, this function immediately
 * returns (successfully).
 *
 * Returns 0 on success, and an appropriate error value otherwise.
 */
int rproc_boot(struct rproc *rproc)
{
	const struct firmware *firmware_p;
	struct device *dev;
	int ret;

	if (!rproc) {
		pr_err("invalid rproc handle\n");
		return -EINVAL;
	}

	dev = rproc->dev;

	ret = mutex_lock_interruptible(&rproc->lock);
	if (ret) {
		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
		return ret;
	}

	/* loading a firmware is required */
	if (!rproc->firmware) {
		dev_err(dev, "%s: no firmware to load\n", __func__);
		ret = -EINVAL;
		goto unlock_mutex;
	}

	/* prevent underlying implementation from being removed */
	if (!try_module_get(dev->driver->owner)) {
		dev_err(dev, "%s: can't get owner\n", __func__);
		ret = -EINVAL;
		goto unlock_mutex;
	}

	/* skip the boot process if rproc is already powered up */
	if (atomic_inc_return(&rproc->power) > 1) {
		ret = 0;
		goto unlock_mutex;
	}

	dev_info(dev, "powering up %s\n", rproc->name);

	/* load firmware */
	ret = request_firmware(&firmware_p, rproc->firmware, dev);
	if (ret < 0) {
		dev_err(dev, "request_firmware failed: %d\n", ret);
		goto downref_rproc;
	}

	ret = rproc_fw_boot(rproc, firmware_p);

	release_firmware(firmware_p);

downref_rproc:
	if (ret) {
		module_put(dev->driver->owner);
		atomic_dec(&rproc->power);
	}
unlock_mutex:
	mutex_unlock(&rproc->lock);
	return ret;
}
EXPORT_SYMBOL(rproc_boot);

/**
 * rproc_shutdown() - power off the remote processor
 * @rproc: the remote processor
 *
 * Power off a remote processor (previously booted with rproc_boot()).
 *
 * In case @rproc is still being used by an additional user(s), then
 * this function will just decrement the power refcount and exit,
 * without really powering off the device.
 *
 * Every call to rproc_boot() must (eventually) be accompanied by a call
 * to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
 *
 * Notes:
 * - we're not decrementing the rproc's refcount, only the power refcount.
 *   which means that the @rproc handle stays valid even after rproc_shutdown()
 *   returns, and users can still use it with a subsequent rproc_boot(), if
 *   needed.
 * - don't call rproc_shutdown() to unroll rproc_get_by_name(), exactly
 *   because rproc_shutdown() _does not_ decrement the refcount of @rproc.
 *   To decrement the refcount of @rproc, use rproc_put() (but _only_ if
 *   you acquired @rproc using rproc_get_by_name()).
 */
void rproc_shutdown(struct rproc *rproc)
{
	struct device *dev = rproc->dev;
	int ret;

	ret = mutex_lock_interruptible(&rproc->lock);
	if (ret) {
		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
		return;
	}

	/* if the remote proc is still needed, bail out */
	if (!atomic_dec_and_test(&rproc->power))
		goto out;

	/* power off the remote processor */
	ret = rproc->ops->stop(rproc);
	if (ret) {
		atomic_inc(&rproc->power);
		dev_err(dev, "can't stop rproc: %d\n", ret);
		goto out;
	}

	/* clean up all acquired resources */
	rproc_resource_cleanup(rproc);

	rproc_disable_iommu(rproc);

	rproc->state = RPROC_OFFLINE;

	dev_info(dev, "stopped remote processor %s\n", rproc->name);

out:
	mutex_unlock(&rproc->lock);
	if (!ret)
		module_put(dev->driver->owner);
}
EXPORT_SYMBOL(rproc_shutdown);

/**
 * rproc_release() - completely deletes the existence of a remote processor
 * @kref: the rproc's kref
 *
 * This function should _never_ be called directly.
 *
 * The only reasonable location to use it is as an argument when kref_put'ing
 * @rproc's refcount.
 *
 * This way it will be called when no one holds a valid pointer to this @rproc
 * anymore (and obviously after it is removed from the rprocs klist).
 *
 * Note: this function is not static because rproc_vdev_release() needs it when
 * it decrements @rproc's refcount.
 */
void rproc_release(struct kref *kref)
{
	struct rproc *rproc = container_of(kref, struct rproc, refcount);

	dev_info(rproc->dev, "removing %s\n", rproc->name);

	rproc_delete_debug_dir(rproc);

	/* at this point no one holds a reference to rproc anymore */
	kfree(rproc);
}

/* will be called when an rproc is added to the rprocs klist */
static void klist_rproc_get(struct klist_node *n)
{
	struct rproc *rproc = container_of(n, struct rproc, node);

	kref_get(&rproc->refcount);
}

/* will be called when an rproc is removed from the rprocs klist */
static void klist_rproc_put(struct klist_node *n)
{
	struct rproc *rproc = container_of(n, struct rproc, node);

	kref_put(&rproc->refcount, rproc_release);
}

static struct rproc *next_rproc(struct klist_iter *i)
{
	struct klist_node *n;

	n = klist_next(i);
	if (!n)
		return NULL;

	return container_of(n, struct rproc, node);
}

/**
 * rproc_get_by_name() - find a remote processor by name and boot it
 * @name: name of the remote processor
 *
 * Finds an rproc handle using the remote processor's name, and then
 * boot it. If it's already powered on, then just immediately return
 * (successfully).
 *
 * Returns the rproc handle on success, and NULL on failure.
 *
 * This function increments the remote processor's refcount, so always
 * use rproc_put() to decrement it back once rproc isn't needed anymore.
 *
 * Note: currently this function (and its counterpart rproc_put()) are not
 * used anymore by the rpmsg subsystem. We need to scrutinize the use cases
 * that still need them, and see if we can migrate them to use the non
 * name-based boot/shutdown interface.
 */
struct rproc *rproc_get_by_name(const char *name)
{
	struct rproc *rproc;
	struct klist_iter i;
	int ret;

	/* find the remote processor, and upref its refcount */
	klist_iter_init(&rprocs, &i);
	while ((rproc = next_rproc(&i)) != NULL)
		if (!strcmp(rproc->name, name)) {
			kref_get(&rproc->refcount);
			break;
		}
	klist_iter_exit(&i);

	/* can't find this rproc ? */
	if (!rproc) {
		pr_err("can't find remote processor %s\n", name);
		return NULL;
	}

	ret = rproc_boot(rproc);
	if (ret < 0) {
		kref_put(&rproc->refcount, rproc_release);
		return NULL;
	}

	return rproc;
}
EXPORT_SYMBOL(rproc_get_by_name);

/**
 * rproc_put() - decrement the refcount of a remote processor, and shut it down
 * @rproc: the remote processor
 *
 * This function tries to shutdown @rproc, and it then decrements its
 * refcount.
 *
 * After this function returns, @rproc may _not_ be used anymore, and its
 * handle should be considered invalid.
 *
 * This function should be called _iff_ the @rproc handle was grabbed by
 * calling rproc_get_by_name().
 */
void rproc_put(struct rproc *rproc)
{
	/* try to power off the remote processor */
	rproc_shutdown(rproc);

	/* downref rproc's refcount */
	kref_put(&rproc->refcount, rproc_release);
}
EXPORT_SYMBOL(rproc_put);

/**
 * rproc_register() - register a remote processor
 * @rproc: the remote processor handle to register
 *
 * Registers @rproc with the remoteproc framework, after it has been
 * allocated with rproc_alloc().
 *
 * This is called by the platform-specific rproc implementation, whenever
 * a new remote processor device is probed.
 *
 * Returns 0 on success and an appropriate error code otherwise.
 *
 * Note: this function initiates an asynchronous firmware loading
 * context, which will look for virtio devices supported by the rproc's
 * firmware.
 *
 * If found, those virtio devices will be created and added, so as a result
 * of registering this remote processor, additional virtio drivers will be
 * probed.
 *
 * Currently, though, we only support a single RPMSG virtio vdev per remote
 * processor.
 */
int rproc_register(struct rproc *rproc)
{
	struct device *dev = rproc->dev;
	int ret = 0;

	/* expose to rproc_get_by_name users */
	klist_add_tail(&rproc->node, &rprocs);

	dev_info(rproc->dev, "%s is available\n", rproc->name);

	/* create debugfs entries */
	rproc_create_debug_dir(rproc);

	/* rproc_unregister() calls must wait until async loader completes */
	init_completion(&rproc->firmware_loading_complete);

	/*
	 * We must retrieve early virtio configuration info from
	 * the firmware (e.g. whether to register a virtio rpmsg device,
	 * what virtio features does it support, ...).
	 *
	 * We're initiating an asynchronous firmware loading, so we can
	 * be built-in kernel code, without hanging the boot process.
	 */
	ret = request_firmware_nowait(THIS_MODULE, FW_ACTION_HOTPLUG,
					rproc->firmware, dev, GFP_KERNEL,
					rproc, rproc_fw_config_virtio);
	if (ret < 0) {
		dev_err(dev, "request_firmware_nowait failed: %d\n", ret);
		complete_all(&rproc->firmware_loading_complete);
		klist_remove(&rproc->node);
	}

	return ret;
}
EXPORT_SYMBOL(rproc_register);

/**
 * rproc_alloc() - allocate a remote processor handle
 * @dev: the underlying device
 * @name: name of this remote processor
 * @ops: platform-specific handlers (mainly start/stop)
 * @firmware: name of firmware file to load
 * @len: length of private data needed by the rproc driver (in bytes)
 *
 * Allocates a new remote processor handle, but does not register
 * it yet.
 *
 * This function should be used by rproc implementations during initialization
 * of the remote processor.
 *
 * After creating an rproc handle using this function, and when ready,
 * implementations should then call rproc_register() to complete
 * the registration of the remote processor.
 *
 * On success the new rproc is returned, and on failure, NULL.
 *
 * Note: _never_ directly deallocate @rproc, even if it was not registered
 * yet. Instead, if you just need to unroll rproc_alloc(), use rproc_free().
 */
struct rproc *rproc_alloc(struct device *dev, const char *name,
				const struct rproc_ops *ops,
				const char *firmware, int len)
{
	struct rproc *rproc;

	if (!dev || !name || !ops)
		return NULL;

	rproc = kzalloc(sizeof(struct rproc) + len, GFP_KERNEL);
	if (!rproc) {
		dev_err(dev, "%s: kzalloc failed\n", __func__);
		return NULL;
	}

	rproc->dev = dev;
	rproc->name = name;
	rproc->ops = ops;
	rproc->firmware = firmware;
	rproc->priv = &rproc[1];

	atomic_set(&rproc->power, 0);

	kref_init(&rproc->refcount);

	mutex_init(&rproc->lock);

	INIT_LIST_HEAD(&rproc->carveouts);
	INIT_LIST_HEAD(&rproc->mappings);
	INIT_LIST_HEAD(&rproc->traces);

	rproc->state = RPROC_OFFLINE;

	return rproc;
}
EXPORT_SYMBOL(rproc_alloc);

/**
 * rproc_free() - free an rproc handle that was allocated by rproc_alloc
 * @rproc: the remote processor handle
 *
 * This function should _only_ be used if @rproc was only allocated,
 * but not registered yet.
 *
 * If @rproc was already successfully registered (by calling rproc_register()),
 * then use rproc_unregister() instead.
 */
void rproc_free(struct rproc *rproc)
{
	kfree(rproc);
}
EXPORT_SYMBOL(rproc_free);

/**
 * rproc_unregister() - unregister a remote processor
 * @rproc: rproc handle to unregister
 *
 * Unregisters a remote processor, and decrements its refcount.
 * If its refcount drops to zero, then @rproc will be freed. If not,
 * it will be freed later once the last reference is dropped.
 *
 * This function should be called when the platform specific rproc
 * implementation decides to remove the rproc device. it should
 * _only_ be called if a previous invocation of rproc_register()
 * has completed successfully.
 *
 * After rproc_unregister() returns, @rproc is _not_ valid anymore and
 * it shouldn't be used. More specifically, don't call rproc_free()
 * or try to directly free @rproc after rproc_unregister() returns;
 * none of these are needed, and calling them is a bug.
 *
 * Returns 0 on success and -EINVAL if @rproc isn't valid.
 */
int rproc_unregister(struct rproc *rproc)
{
	if (!rproc)
		return -EINVAL;

	/* if rproc is just being registered, wait */
	wait_for_completion(&rproc->firmware_loading_complete);

	/* was an rpmsg vdev created ? */
	if (rproc->rvdev)
		rproc_remove_rpmsg_vdev(rproc);

	klist_remove(&rproc->node);

	kref_put(&rproc->refcount, rproc_release);

	return 0;
}
EXPORT_SYMBOL(rproc_unregister);

static int __init remoteproc_init(void)
{
	rproc_init_debugfs();
	return 0;
}
module_init(remoteproc_init);

static void __exit remoteproc_exit(void)
{
	rproc_exit_debugfs();
}
module_exit(remoteproc_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Generic Remote Processor Framework");