/*
 * AMD Cryptographic Coprocessor (CCP) driver
 *
 * Copyright (C) 2013 Advanced Micro Devices, Inc.
 *
 * Author: Tom Lendacky <thomas.lendacky@amd.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.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/hw_random.h>
#include <linux/cpu.h>
#include <asm/cpu_device_id.h>
#include <linux/ccp.h>

#include "ccp-dev.h"

MODULE_AUTHOR("Tom Lendacky <thomas.lendacky@amd.com>");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0.0");
MODULE_DESCRIPTION("AMD Cryptographic Coprocessor driver");

struct ccp_tasklet_data {
        struct completion completion;
        struct ccp_cmd *cmd;
};


static struct ccp_device *ccp_dev;
static inline struct ccp_device *ccp_get_device(void)
{
        return ccp_dev;
}

static inline void ccp_add_device(struct ccp_device *ccp)
{
        ccp_dev = ccp;
}

static inline void ccp_del_device(struct ccp_device *ccp)
{
        ccp_dev = NULL;
}

/**
 * ccp_enqueue_cmd - queue an operation for processing by the CCP
 *
 * @cmd: ccp_cmd struct to be processed
 *
 * Queue a cmd to be processed by the CCP. If queueing the cmd
 * would exceed the defined length of the cmd queue the cmd will
 * only be queued if the CCP_CMD_MAY_BACKLOG flag is set and will
 * result in a return code of -EBUSY.
 *
 * The callback routine specified in the ccp_cmd struct will be
 * called to notify the caller of completion (if the cmd was not
 * backlogged) or advancement out of the backlog. If the cmd has
 * advanced out of the backlog the "err" value of the callback
 * will be -EINPROGRESS. Any other "err" value during callback is
 * the result of the operation.
 *
 * The cmd has been successfully queued if:
 *   the return code is -EINPROGRESS or
 *   the return code is -EBUSY and CCP_CMD_MAY_BACKLOG flag is set
 */
int ccp_enqueue_cmd(struct ccp_cmd *cmd)
{
        struct ccp_device *ccp = ccp_get_device();
        unsigned long flags;
        unsigned int i;
        int ret;

        if (!ccp)
                return -ENODEV;

        /* Caller must supply a callback routine */
        if (!cmd->callback)
                return -EINVAL;

        cmd->ccp = ccp;

        spin_lock_irqsave(&ccp->cmd_lock, flags);

        i = ccp->cmd_q_count;

        if (ccp->cmd_count >= MAX_CMD_QLEN) {
                ret = -EBUSY;
                if (cmd->flags & CCP_CMD_MAY_BACKLOG)
                        list_add_tail(&cmd->entry, &ccp->backlog);
        } else {
                ret = -EINPROGRESS;
                ccp->cmd_count++;
                list_add_tail(&cmd->entry, &ccp->cmd);

                /* Find an idle queue */
                if (!ccp->suspending) {
                        for (i = 0; i < ccp->cmd_q_count; i++) {
                                if (ccp->cmd_q[i].active)
                                        continue;

                                break;
                        }
                }
        }

        spin_unlock_irqrestore(&ccp->cmd_lock, flags);

        /* If we found an idle queue, wake it up */
        if (i < ccp->cmd_q_count)
                wake_up_process(ccp->cmd_q[i].kthread);

        return ret;
}
EXPORT_SYMBOL_GPL(ccp_enqueue_cmd);

static void ccp_do_cmd_backlog(struct work_struct *work)
{
        struct ccp_cmd *cmd = container_of(work, struct ccp_cmd, work);
        struct ccp_device *ccp = cmd->ccp;
        unsigned long flags;
        unsigned int i;

        cmd->callback(cmd->data, -EINPROGRESS);

        spin_lock_irqsave(&ccp->cmd_lock, flags);

        ccp->cmd_count++;
        list_add_tail(&cmd->entry, &ccp->cmd);

        /* Find an idle queue */
        for (i = 0; i < ccp->cmd_q_count; i++) {
                if (ccp->cmd_q[i].active)
                        continue;

                break;
        }

        spin_unlock_irqrestore(&ccp->cmd_lock, flags);

        /* If we found an idle queue, wake it up */
        if (i < ccp->cmd_q_count)
                wake_up_process(ccp->cmd_q[i].kthread);
}

static struct ccp_cmd *ccp_dequeue_cmd(struct ccp_cmd_queue *cmd_q)
{
        struct ccp_device *ccp = cmd_q->ccp;
        struct ccp_cmd *cmd = NULL;
        struct ccp_cmd *backlog = NULL;
        unsigned long flags;

        spin_lock_irqsave(&ccp->cmd_lock, flags);

        cmd_q->active = 0;

        if (ccp->suspending) {
                cmd_q->suspended = 1;

                spin_unlock_irqrestore(&ccp->cmd_lock, flags);
                wake_up_interruptible(&ccp->suspend_queue);

                return NULL;
        }

        if (ccp->cmd_count) {
                cmd_q->active = 1;

                cmd = list_first_entry(&ccp->cmd, struct ccp_cmd, entry);
                list_del(&cmd->entry);

                ccp->cmd_count--;
        }

        if (!list_empty(&ccp->backlog)) {
                backlog = list_first_entry(&ccp->backlog, struct ccp_cmd,
                                           entry);
                list_del(&backlog->entry);
        }

        spin_unlock_irqrestore(&ccp->cmd_lock, flags);

        if (backlog) {
                INIT_WORK(&backlog->work, ccp_do_cmd_backlog);
                schedule_work(&backlog->work);
        }

        return cmd;
}

static void ccp_do_cmd_complete(unsigned long data)
{
        struct ccp_tasklet_data *tdata = (struct ccp_tasklet_data *)data;
        struct ccp_cmd *cmd = tdata->cmd;

        cmd->callback(cmd->data, cmd->ret);
        complete(&tdata->completion);
}

static int ccp_cmd_queue_thread(void *data)
{
        struct ccp_cmd_queue *cmd_q = (struct ccp_cmd_queue *)data;
        struct ccp_cmd *cmd;
        struct ccp_tasklet_data tdata;
        struct tasklet_struct tasklet;

        tasklet_init(&tasklet, ccp_do_cmd_complete, (unsigned long)&tdata);

        set_current_state(TASK_INTERRUPTIBLE);
        while (!kthread_should_stop()) {
                schedule();

                set_current_state(TASK_INTERRUPTIBLE);

                cmd = ccp_dequeue_cmd(cmd_q);
                if (!cmd)
                        continue;

                __set_current_state(TASK_RUNNING);

                /* Execute the command */
                cmd->ret = ccp_run_cmd(cmd_q, cmd);

                /* Schedule the completion callback */
                tdata.cmd = cmd;
                init_completion(&tdata.completion);
                tasklet_schedule(&tasklet);
                wait_for_completion(&tdata.completion);
        }

        __set_current_state(TASK_RUNNING);

        return 0;
}

static int ccp_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)
{
        struct ccp_device *ccp = container_of(rng, struct ccp_device, hwrng);
        u32 trng_value;
        int len = min_t(int, sizeof(trng_value), max);

        /*
         * Locking is provided by the caller so we can update device
         * hwrng-related fields safely
         */
        trng_value = ioread32(ccp->io_regs + TRNG_OUT_REG);
        if (!trng_value) {
                /* Zero is returned if not data is available or if a
                 * bad-entropy error is present. Assume an error if
                 * we exceed TRNG_RETRIES reads of zero.
                 */
                if (ccp->hwrng_retries++ > TRNG_RETRIES)
                        return -EIO;

                return 0;
        }

        /* Reset the counter and save the rng value */
        ccp->hwrng_retries = 0;
        memcpy(data, &trng_value, len);

        return len;
}

/**
 * ccp_alloc_struct - allocate and initialize the ccp_device struct
 *
 * @dev: device struct of the CCP
 */
struct ccp_device *ccp_alloc_struct(struct device *dev)
{
        struct ccp_device *ccp;

        ccp = kzalloc(sizeof(*ccp), GFP_KERNEL);
        if (ccp == NULL) {
                dev_err(dev, "unable to allocate device struct\n");
                return NULL;
        }
        ccp->dev = dev;

        INIT_LIST_HEAD(&ccp->cmd);
        INIT_LIST_HEAD(&ccp->backlog);

        spin_lock_init(&ccp->cmd_lock);
        mutex_init(&ccp->req_mutex);
        mutex_init(&ccp->ksb_mutex);
        ccp->ksb_count = KSB_COUNT;
        ccp->ksb_start = 0;

        return ccp;
}

/**
 * ccp_init - initialize the CCP device
 *
 * @ccp: ccp_device struct
 */
int ccp_init(struct ccp_device *ccp)
{
        struct device *dev = ccp->dev;
        struct ccp_cmd_queue *cmd_q;
        struct dma_pool *dma_pool;
        char dma_pool_name[MAX_DMAPOOL_NAME_LEN];
        unsigned int qmr, qim, i;
        int ret;

        /* Find available queues */
        qim = 0;
        qmr = ioread32(ccp->io_regs + Q_MASK_REG);
        for (i = 0; i < MAX_HW_QUEUES; i++) {
                if (!(qmr & (1 << i)))
                        continue;

                /* Allocate a dma pool for this queue */
                snprintf(dma_pool_name, sizeof(dma_pool_name), "ccp_q%d", i);
                dma_pool = dma_pool_create(dma_pool_name, dev,
                                           CCP_DMAPOOL_MAX_SIZE,
                                           CCP_DMAPOOL_ALIGN, 0);
                if (!dma_pool) {
                        dev_err(dev, "unable to allocate dma pool\n");
                        ret = -ENOMEM;
                        goto e_pool;
                }

                cmd_q = &ccp->cmd_q[ccp->cmd_q_count];
                ccp->cmd_q_count++;

                cmd_q->ccp = ccp;
                cmd_q->id = i;
                cmd_q->dma_pool = dma_pool;

                /* Reserve 2 KSB regions for the queue */
                cmd_q->ksb_key = KSB_START + ccp->ksb_start++;
                cmd_q->ksb_ctx = KSB_START + ccp->ksb_start++;
                ccp->ksb_count -= 2;

                /* Preset some register values and masks that are queue
                 * number dependent
                 */
                cmd_q->reg_status = ccp->io_regs + CMD_Q_STATUS_BASE +
                                    (CMD_Q_STATUS_INCR * i);
                cmd_q->reg_int_status = ccp->io_regs + CMD_Q_INT_STATUS_BASE +
                                        (CMD_Q_STATUS_INCR * i);
                cmd_q->int_ok = 1 << (i * 2);
                cmd_q->int_err = 1 << ((i * 2) + 1);

                cmd_q->free_slots = CMD_Q_DEPTH(ioread32(cmd_q->reg_status));

                init_waitqueue_head(&cmd_q->int_queue);

                /* Build queue interrupt mask (two interrupts per queue) */
                qim |= cmd_q->int_ok | cmd_q->int_err;

                dev_dbg(dev, "queue #%u available\n", i);
        }
        if (ccp->cmd_q_count == 0) {
                dev_notice(dev, "no command queues available\n");
                ret = -EIO;
                goto e_pool;
        }
        dev_notice(dev, "%u command queues available\n", ccp->cmd_q_count);

        /* Disable and clear interrupts until ready */
        iowrite32(0x00, ccp->io_regs + IRQ_MASK_REG);
        for (i = 0; i < ccp->cmd_q_count; i++) {
                cmd_q = &ccp->cmd_q[i];

                ioread32(cmd_q->reg_int_status);
                ioread32(cmd_q->reg_status);
        }
        iowrite32(qim, ccp->io_regs + IRQ_STATUS_REG);

        /* Request an irq */
        ret = ccp->get_irq(ccp);
        if (ret) {
                dev_err(dev, "unable to allocate an IRQ\n");
                goto e_pool;
        }

        /* Initialize the queues used to wait for KSB space and suspend */
        init_waitqueue_head(&ccp->ksb_queue);
        init_waitqueue_head(&ccp->suspend_queue);

        /* Create a kthread for each queue */
        for (i = 0; i < ccp->cmd_q_count; i++) {
                struct task_struct *kthread;

                cmd_q = &ccp->cmd_q[i];

                kthread = kthread_create(ccp_cmd_queue_thread, cmd_q,
                                         "ccp-q%u", cmd_q->id);
                if (IS_ERR(kthread)) {
                        dev_err(dev, "error creating queue thread (%ld)\n",
                                PTR_ERR(kthread));
                        ret = PTR_ERR(kthread);
                        goto e_kthread;
                }

                cmd_q->kthread = kthread;
                wake_up_process(kthread);
        }

        /* Register the RNG */
        ccp->hwrng.name = "ccp-rng";
        ccp->hwrng.read = ccp_trng_read;
        ret = hwrng_register(&ccp->hwrng);
        if (ret) {
                dev_err(dev, "error registering hwrng (%d)\n", ret);
                goto e_kthread;
        }

        /* Make the device struct available before enabling interrupts */
        ccp_add_device(ccp);

        /* Enable interrupts */
        iowrite32(qim, ccp->io_regs + IRQ_MASK_REG);

        return 0;

e_kthread:
        for (i = 0; i < ccp->cmd_q_count; i++)
                if (ccp->cmd_q[i].kthread)
                        kthread_stop(ccp->cmd_q[i].kthread);

        ccp->free_irq(ccp);

e_pool:
        for (i = 0; i < ccp->cmd_q_count; i++)
                dma_pool_destroy(ccp->cmd_q[i].dma_pool);

        return ret;
}

/**
 * ccp_destroy - tear down the CCP device
 *
 * @ccp: ccp_device struct
 */
void ccp_destroy(struct ccp_device *ccp)
{
        struct ccp_cmd_queue *cmd_q;
        struct ccp_cmd *cmd;
        unsigned int qim, i;

        /* Remove general access to the device struct */
        ccp_del_device(ccp);

        /* Unregister the RNG */
        hwrng_unregister(&ccp->hwrng);

        /* Stop the queue kthreads */
        for (i = 0; i < ccp->cmd_q_count; i++)
                if (ccp->cmd_q[i].kthread)
                        kthread_stop(ccp->cmd_q[i].kthread);

        /* Build queue interrupt mask (two interrupt masks per queue) */
        qim = 0;
        for (i = 0; i < ccp->cmd_q_count; i++) {
                cmd_q = &ccp->cmd_q[i];
                qim |= cmd_q->int_ok | cmd_q->int_err;
        }

        /* Disable and clear interrupts */
        iowrite32(0x00, ccp->io_regs + IRQ_MASK_REG);
        for (i = 0; i < ccp->cmd_q_count; i++) {
                cmd_q = &ccp->cmd_q[i];

                ioread32(cmd_q->reg_int_status);
                ioread32(cmd_q->reg_status);
        }
        iowrite32(qim, ccp->io_regs + IRQ_STATUS_REG);

        ccp->free_irq(ccp);

        for (i = 0; i < ccp->cmd_q_count; i++)
                dma_pool_destroy(ccp->cmd_q[i].dma_pool);

        /* Flush the cmd and backlog queue */
        while (!list_empty(&ccp->cmd)) {
                /* Invoke the callback directly with an error code */
                cmd = list_first_entry(&ccp->cmd, struct ccp_cmd, entry);
                list_del(&cmd->entry);
                cmd->callback(cmd->data, -ENODEV);
        }
        while (!list_empty(&ccp->backlog)) {
                /* Invoke the callback directly with an error code */
                cmd = list_first_entry(&ccp->backlog, struct ccp_cmd, entry);
                list_del(&cmd->entry);
                cmd->callback(cmd->data, -ENODEV);
        }
}

/**
 * ccp_irq_handler - handle interrupts generated by the CCP device
 *
 * @irq: the irq associated with the interrupt
 * @data: the data value supplied when the irq was created
 */
irqreturn_t ccp_irq_handler(int irq, void *data)
{
        struct device *dev = data;
        struct ccp_device *ccp = dev_get_drvdata(dev);
        struct ccp_cmd_queue *cmd_q;
        u32 q_int, status;
        unsigned int i;

        status = ioread32(ccp->io_regs + IRQ_STATUS_REG);

        for (i = 0; i < ccp->cmd_q_count; i++) {
                cmd_q = &ccp->cmd_q[i];

                q_int = status & (cmd_q->int_ok | cmd_q->int_err);
                if (q_int) {
                        cmd_q->int_status = status;
                        cmd_q->q_status = ioread32(cmd_q->reg_status);
                        cmd_q->q_int_status = ioread32(cmd_q->reg_int_status);

                        /* On error, only save the first error value */
                        if ((q_int & cmd_q->int_err) && !cmd_q->cmd_error)
                                cmd_q->cmd_error = CMD_Q_ERROR(cmd_q->q_status);

                        cmd_q->int_rcvd = 1;

                        /* Acknowledge the interrupt and wake the kthread */
                        iowrite32(q_int, ccp->io_regs + IRQ_STATUS_REG);
                        wake_up_interruptible(&cmd_q->int_queue);
                }
        }

        return IRQ_HANDLED;
}

#ifdef CONFIG_PM
bool ccp_queues_suspended(struct ccp_device *ccp)
{
        unsigned int suspended = 0;
        unsigned long flags;
        unsigned int i;

        spin_lock_irqsave(&ccp->cmd_lock, flags);

        for (i = 0; i < ccp->cmd_q_count; i++)
                if (ccp->cmd_q[i].suspended)
                        suspended++;

        spin_unlock_irqrestore(&ccp->cmd_lock, flags);

        return ccp->cmd_q_count == suspended;
}
#endif

static const struct x86_cpu_id ccp_support[] = {
        { X86_VENDOR_AMD, 22, },
};

static int __init ccp_mod_init(void)
{
        struct cpuinfo_x86 *cpuinfo = &boot_cpu_data;
        int ret;

        if (!x86_match_cpu(ccp_support))
                return -ENODEV;

        switch (cpuinfo->x86) {
        case 22:
                if ((cpuinfo->x86_model < 48) || (cpuinfo->x86_model > 63))
                        return -ENODEV;

                ret = ccp_pci_init();
                if (ret)
                        return ret;

                /* Don't leave the driver loaded if init failed */
                if (!ccp_get_device()) {
                        ccp_pci_exit();
                        return -ENODEV;
                }

                return 0;

                break;
        }

        return -ENODEV;
}

static void __exit ccp_mod_exit(void)
{
        struct cpuinfo_x86 *cpuinfo = &boot_cpu_data;

        switch (cpuinfo->x86) {
        case 22:
                ccp_pci_exit();
                break;
        }
}

module_init(ccp_mod_init);
module_exit(ccp_mod_exit);