remoteproc: add framework for controlling remote processors

[mirror_ubuntu-zesty-kernel.git] / drivers / remoteproc / 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_err(dev, "iommu not found\n");
                return -ENODEV;
        }

        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 = 0;

        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");