// SPDX-License-Identifier: GPL-2.0
/*
 * HMS Anybus-S Host Driver
 *
 * Copyright (C) 2018 Arcx Inc
 */

/*
 * Architecture Overview
 * =====================
 * This driver (running on the CPU/SoC) and the Anybus-S card communicate
 * by reading and writing data to/from the Anybus-S Dual-Port RAM (dpram).
 * This is memory connected to both the SoC and Anybus-S card, which both sides
 * can access freely and concurrently.
 *
 * Synchronization happens by means of two registers located in the dpram:
 * IND_AB: written exclusively by the Anybus card; and
 * IND_AP: written exclusively by this driver.
 *
 * Communication happens using one of the following mechanisms:
 * 1. reserve, read/write, release dpram memory areas:
 *      using an IND_AB/IND_AP protocol, the driver is able to reserve certain
 *      memory areas. no dpram memory can be read or written except if reserved.
 *      (with a few limited exceptions)
 * 2. send and receive data structures via a shared mailbox:
 *      using an IND_AB/IND_AP protocol, the driver and Anybus card are able to
 *      exchange commands and responses using a shared mailbox.
 * 3. receive software interrupts:
 *      using an IND_AB/IND_AP protocol, the Anybus card is able to notify the
 *      driver of certain events such as: bus online/offline, data available.
 *      note that software interrupt event bits are located in a memory area
 *      which must be reserved before it can be accessed.
 *
 * The manual[1] is silent on whether these mechanisms can happen concurrently,
 * or how they should be synchronized. However, section 13 (Driver Example)
 * provides the following suggestion for developing a driver:
 * a) an interrupt handler which updates global variables;
 * b) a continuously-running task handling area requests (1 above)
 * c) a continuously-running task handling mailbox requests (2 above)
 * The example conspicuously leaves out software interrupts (3 above), which
 * is the thorniest issue to get right (see below).
 *
 * The naive, straightforward way to implement this would be:
 * - create an isr which updates shared variables;
 * - create a work_struct which handles software interrupts on a queue;
 * - create a function which does reserve/update/unlock in a loop;
 * - create a function which does mailbox send/receive in a loop;
 * - call the above functions from the driver's read/write/ioctl;
 * - synchronize using mutexes/spinlocks:
 *      + only one area request at a time
 *      + only one mailbox request at a time
 *      + protect AB_IND, AB_IND against data hazards (e.g. read-after-write)
 *
 * Unfortunately, the presence of the software interrupt causes subtle yet
 * considerable synchronization issues; especially problematic is the
 * requirement to reserve/release the area which contains the status bits.
 *
 * The driver architecture presented here sidesteps these synchronization issues
 * by accessing the dpram from a single kernel thread only. User-space throws
 * "tasks" (i.e. 1, 2 above) into a task queue, waits for their completion,
 * and the kernel thread runs them to completion.
 *
 * Each task has a task_function, which is called/run by the queue thread.
 * That function communicates with the Anybus card, and returns either
 * 0 (OK), a negative error code (error), or -EINPROGRESS (waiting).
 * On OK or error, the queue thread completes and dequeues the task,
 * which also releases the user space thread which may still be waiting for it.
 * On -EINPROGRESS (waiting), the queue thread will leave the task on the queue,
 * and revisit (call again) whenever an interrupt event comes in.
 *
 * Each task has a state machine, which is run by calling its task_function.
 * It ensures that the task will go through its various stages over time,
 * returning -EINPROGRESS if it wants to wait for an event to happen.
 *
 * Note that according to the manual's driver example, the following operations
 * may run independent of each other:
 * - area reserve/read/write/release    (point 1 above)
 * - mailbox operations                 (point 2 above)
 * - switching power on/off
 *
 * To allow them to run independently, each operation class gets its own queue.
 *
 * Userspace processes A, B, C, D post tasks to the appropriate queue,
 * and wait for task completion:
 *
 *      process A       B       C       D
 *              |       |       |       |
 *              v       v       v       v
 *      |<----- ========================================
 *      |               |          |            |
 *      |               v          v            v-------<-------+
 *      |       +--------------------------------------+        |
 *      |       | power q     | mbox q    | area q     |        |
 *      |       |------------|------------|------------|        |
 *      |       | task       | task       | task       |        |
 *      |       | task       | task       | task       |        |
 *      |       | task wait  | task wait  | task wait  |        |
 *      |       +--------------------------------------+        |
 *      |               ^          ^            ^               |
 *      |               |          |            |               ^
 *      |       +--------------------------------------+        |
 *      |       |            queue thread              |        |
 *      |       |--------------------------------------|        |
 *      |       | single-threaded:                     |        |
 *      |       | loop:                                |        |
 *      v       |   for each queue:                    |        |
 *      |       |     run task state machine           |        |
 *      |       |     if task waiting:                 |        |
 *      |       |       leave on queue                 |        |
 *      |       |     if task done:                    |        |
 *      |       |       complete task, remove from q   |        |
 *      |       |   if software irq event bits set:    |        |
 *      |       |     notify userspace                 |        |
 *      |       |     post clear event bits task------>|>-------+
 *      |       |   wait for IND_AB changed event OR   |
 *      |       |            task added event     OR   |
 *      |       |            timeout                   |
 *      |       | end loop                             |
 *      |       +--------------------------------------+
 *      |       +               wake up                +
 *      |       +--------------------------------------+
 *      |               ^                       ^
 *      |               |                       |
 *      +-------->-------                       |
 *                                              |
 *              +--------------------------------------+
 *              |       interrupt service routine      |
 *              |--------------------------------------|
 *              | wake up queue thread on IND_AB change|
 *              +--------------------------------------+
 *
 * Note that the Anybus interrupt is dual-purpose:
 * - after a reset, triggered when the card becomes ready;
 * - during normal operation, triggered when AB_IND changes.
 * This is why the interrupt service routine doesn't just wake up the
 * queue thread, but also completes the card_boot completion.
 *
 * [1] https://www.anybus.com/docs/librariesprovider7/default-document-library/
 *      manuals-design-guides/hms-hmsi-27-275.pdf
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/atomic.h>
#include <linux/kthread.h>
#include <linux/kfifo.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/regmap.h>
#include <linux/of.h>
#include <linux/random.h>
#include <linux/kref.h>
#include <linux/of_address.h>

/* move to <linux/anybuss-*.h> when taking this out of staging */
#include "anybuss-client.h"
#include "anybuss-controller.h"

#define DPRAM_SIZE              0x800
#define MAX_MBOX_MSG_SZ         0x0FF
#define TIMEOUT                 (HZ * 2)
#define MAX_DATA_AREA_SZ        0x200
#define MAX_FBCTRL_AREA_SZ      0x1BE

#define REG_BOOTLOADER_V        0x7C0
#define REG_API_V               0x7C2
#define REG_FIELDBUS_V          0x7C4
#define REG_SERIAL_NO           0x7C6
#define REG_FIELDBUS_TYPE       0x7CC
#define REG_MODULE_SW_V         0x7CE
#define REG_IND_AB              0x7FF
#define REG_IND_AP              0x7FE
#define REG_EVENT_CAUSE         0x7ED
#define MBOX_IN_AREA            0x400
#define MBOX_OUT_AREA           0x520
#define DATA_IN_AREA            0x000
#define DATA_OUT_AREA           0x200
#define FBCTRL_AREA             0x640

#define EVENT_CAUSE_DC          0x01
#define EVENT_CAUSE_FBOF        0x02
#define EVENT_CAUSE_FBON        0x04

#define IND_AB_UPDATED          0x08
#define IND_AX_MIN              0x80
#define IND_AX_MOUT             0x40
#define IND_AX_IN               0x04
#define IND_AX_OUT              0x02
#define IND_AX_FBCTRL           0x01
#define IND_AP_LOCK             0x08
#define IND_AP_ACTION           0x10
#define IND_AX_EVNT             0x20
#define IND_AP_ABITS            (IND_AX_IN | IND_AX_OUT | \
                                        IND_AX_FBCTRL | \
                                        IND_AP_ACTION | IND_AP_LOCK)

#define INFO_TYPE_FB            0x0002
#define INFO_TYPE_APP           0x0001
#define INFO_COMMAND            0x4000

#define OP_MODE_FBFC            0x0002
#define OP_MODE_FBS             0x0004
#define OP_MODE_CD              0x0200

#define CMD_START_INIT          0x0001
#define CMD_ANYBUS_INIT         0x0002
#define CMD_END_INIT            0x0003

/*
 * ---------------------------------------------------------------
 * Anybus mailbox messages - definitions
 * ---------------------------------------------------------------
 * note that we're depending on the layout of these structures being
 * exactly as advertised.
 */

struct anybus_mbox_hdr {
        __be16 id;
        __be16 info;
        __be16 cmd_num;
        __be16 data_size;
        __be16 frame_count;
        __be16 frame_num;
        __be16 offset_high;
        __be16 offset_low;
        __be16 extended[8];
};

struct msg_anybus_init {
        __be16 input_io_len;
        __be16 input_dpram_len;
        __be16 input_total_len;
        __be16 output_io_len;
        __be16 output_dpram_len;
        __be16 output_total_len;
        __be16 op_mode;
        __be16 notif_config;
        __be16 wd_val;
};

/* ------------- ref counted tasks ------------- */

struct ab_task;
typedef int (*ab_task_fn_t)(struct anybuss_host *cd,
                                        struct ab_task *t);
typedef void (*ab_done_fn_t)(struct anybuss_host *cd);

struct area_priv {
        bool is_write;
        u16 flags;
        u16 addr;
        size_t count;
        u8 buf[MAX_DATA_AREA_SZ];
};

struct mbox_priv {
        struct anybus_mbox_hdr hdr;
        size_t msg_out_sz;
        size_t msg_in_sz;
        u8 msg[MAX_MBOX_MSG_SZ];
};

struct ab_task {
        struct kmem_cache       *cache;
        struct kref             refcount;
        ab_task_fn_t            task_fn;
        ab_done_fn_t            done_fn;
        int                     result;
        struct completion       done;
        unsigned long           start_jiffies;
        union {
                struct area_priv area_pd;
                struct mbox_priv mbox_pd;
        };
};

static struct ab_task *ab_task_create_get(struct kmem_cache *cache,
                                          ab_task_fn_t task_fn)
{
        struct ab_task *t;

        t = kmem_cache_alloc(cache, GFP_KERNEL);
        if (!t)
                return NULL;
        t->cache = cache;
        kref_init(&t->refcount);
        t->task_fn = task_fn;
        t->done_fn = NULL;
        t->result = 0;
        init_completion(&t->done);
        return t;
}

static void __ab_task_destroy(struct kref *refcount)
{
        struct ab_task *t = container_of(refcount, struct ab_task, refcount);
        struct kmem_cache *cache = t->cache;

        kmem_cache_free(cache, t);
}

static void ab_task_put(struct ab_task *t)
{
        kref_put(&t->refcount, __ab_task_destroy);
}

static struct ab_task *__ab_task_get(struct ab_task *t)
{
        kref_get(&t->refcount);
        return t;
}

static void __ab_task_finish(struct ab_task *t, struct anybuss_host *cd)
{
        if (t->done_fn)
                t->done_fn(cd);
        complete(&t->done);
}

static void
ab_task_dequeue_finish_put(struct kfifo *q, struct anybuss_host *cd)
{
        int ret;
        struct ab_task *t;

        ret = kfifo_out(q, &t, sizeof(t));
        WARN_ON(!ret);
        __ab_task_finish(t, cd);
        ab_task_put(t);
}

static int
ab_task_enqueue(struct ab_task *t, struct kfifo *q, spinlock_t *slock,
                wait_queue_head_t *wq)
{
        int ret;

        t->start_jiffies = jiffies;
        __ab_task_get(t);
        ret = kfifo_in_spinlocked(q, &t, sizeof(t), slock);
        if (!ret) {
                ab_task_put(t);
                return -ENOMEM;
        }
        wake_up(wq);
        return 0;
}

static int
ab_task_enqueue_wait(struct ab_task *t, struct kfifo *q, spinlock_t *slock,
                     wait_queue_head_t *wq)
{
        int ret;

        ret = ab_task_enqueue(t, q, slock, wq);
        if (ret)
                return ret;
        ret = wait_for_completion_interruptible(&t->done);
        if (ret)
                return ret;
        return t->result;
}

/* ------------------------ anybus hardware ------------------------ */

struct anybuss_host {
        struct device *dev;
        struct anybuss_client *client;
        void (*reset)(struct device *dev, bool assert);
        struct regmap *regmap;
        int irq;
        int host_idx;
        struct task_struct *qthread;
        wait_queue_head_t wq;
        struct completion card_boot;
        atomic_t ind_ab;
        spinlock_t qlock; /* protects IN side of powerq, mboxq, areaq */
        struct kmem_cache *qcache;
        struct kfifo qs[3];
        struct kfifo *powerq;
        struct kfifo *mboxq;
        struct kfifo *areaq;
        bool power_on;
        bool softint_pending;
};

static void reset_assert(struct anybuss_host *cd)
{
        cd->reset(cd->dev, true);
}

static void reset_deassert(struct anybuss_host *cd)
{
        cd->reset(cd->dev, false);
}

static int test_dpram(struct regmap *regmap)
{
        int i;
        unsigned int val;

        for (i = 0; i < DPRAM_SIZE; i++)
                regmap_write(regmap, i, (u8)i);
        for (i = 0; i < DPRAM_SIZE; i++) {
                regmap_read(regmap, i, &val);
                if ((u8)val != (u8)i)
                        return -EIO;
        }
        return 0;
}

static int read_ind_ab(struct regmap *regmap)
{
        unsigned long timeout = jiffies + HZ / 2;
        unsigned int a, b, i = 0;

        while (time_before_eq(jiffies, timeout)) {
                regmap_read(regmap, REG_IND_AB, &a);
                regmap_read(regmap, REG_IND_AB, &b);
                if (likely(a == b))
                        return (int)a;
                if (i < 10) {
                        cpu_relax();
                        i++;
                } else {
                        usleep_range(500, 1000);
                }
        }
        WARN(1, "IND_AB register not stable");
        return -ETIMEDOUT;
}

static int write_ind_ap(struct regmap *regmap, unsigned int ind_ap)
{
        unsigned long timeout = jiffies + HZ / 2;
        unsigned int v, i = 0;

        while (time_before_eq(jiffies, timeout)) {
                regmap_write(regmap, REG_IND_AP, ind_ap);
                regmap_read(regmap, REG_IND_AP, &v);
                if (likely(ind_ap == v))
                        return 0;
                if (i < 10) {
                        cpu_relax();
                        i++;
                } else {
                        usleep_range(500, 1000);
                }
        }
        WARN(1, "IND_AP register not stable");
        return -ETIMEDOUT;
}

static irqreturn_t irq_handler(int irq, void *data)
{
        struct anybuss_host *cd = data;
        int ind_ab;

        /*
         * irq handler needs exclusive access to the IND_AB register,
         * because the act of reading the register acks the interrupt.
         *
         * store the register value in cd->ind_ab (an atomic_t), so that the
         * queue thread is able to read it without causing an interrupt ack
         * side-effect (and without spuriously acking an interrupt).
         */
        ind_ab = read_ind_ab(cd->regmap);
        if (ind_ab < 0)
                return IRQ_NONE;
        atomic_set(&cd->ind_ab, ind_ab);
        complete(&cd->card_boot);
        wake_up(&cd->wq);
        return IRQ_HANDLED;
}

/* ------------------------ power on/off tasks --------------------- */

static int task_fn_power_off(struct anybuss_host *cd,
                             struct ab_task *t)
{
        struct anybuss_client *client = cd->client;

        if (!cd->power_on)
                return 0;
        disable_irq(cd->irq);
        reset_assert(cd);
        atomic_set(&cd->ind_ab, IND_AB_UPDATED);
        if (client->on_online_changed)
                client->on_online_changed(client, false);
        cd->power_on = false;
        return 0;
}

static int task_fn_power_on_2(struct anybuss_host *cd,
                              struct ab_task *t)
{
        if (completion_done(&cd->card_boot)) {
                cd->power_on = true;
                return 0;
        }
        if (time_after(jiffies, t->start_jiffies + TIMEOUT)) {
                disable_irq(cd->irq);
                reset_assert(cd);
                dev_err(cd->dev, "power on timed out");
                return -ETIMEDOUT;
        }
        return -EINPROGRESS;
}

static int task_fn_power_on(struct anybuss_host *cd,
                            struct ab_task *t)
{
        unsigned int dummy;

        if (cd->power_on)
                return 0;
        /*
         * anybus docs: prevent false 'init done' interrupt by
         * doing a dummy read of IND_AB register while in reset.
         */
        regmap_read(cd->regmap, REG_IND_AB, &dummy);
        reinit_completion(&cd->card_boot);
        enable_irq(cd->irq);
        reset_deassert(cd);
        t->task_fn = task_fn_power_on_2;
        return -EINPROGRESS;
}

int anybuss_set_power(struct anybuss_client *client, bool power_on)
{
        struct anybuss_host *cd = client->host;
        struct ab_task *t;
        int err;

        t = ab_task_create_get(cd->qcache, power_on ?
                                task_fn_power_on : task_fn_power_off);
        if (!t)
                return -ENOMEM;
        err = ab_task_enqueue_wait(t, cd->powerq, &cd->qlock, &cd->wq);
        ab_task_put(t);
        return err;
}
EXPORT_SYMBOL_GPL(anybuss_set_power);

/* ---------------------------- area tasks ------------------------ */

static int task_fn_area_3(struct anybuss_host *cd, struct ab_task *t)
{
        struct area_priv *pd = &t->area_pd;

        if (!cd->power_on)
                return -EIO;
        if (atomic_read(&cd->ind_ab) & pd->flags) {
                /* area not released yet */
                if (time_after(jiffies, t->start_jiffies + TIMEOUT))
                        return -ETIMEDOUT;
                return -EINPROGRESS;
        }
        return 0;
}

static int task_fn_area_2(struct anybuss_host *cd, struct ab_task *t)
{
        struct area_priv *pd = &t->area_pd;
        unsigned int ind_ap;
        int ret;

        if (!cd->power_on)
                return -EIO;
        regmap_read(cd->regmap, REG_IND_AP, &ind_ap);
        if (!(atomic_read(&cd->ind_ab) & pd->flags)) {
                /* we don't own the area yet */
                if (time_after(jiffies, t->start_jiffies + TIMEOUT)) {
                        dev_warn(cd->dev, "timeout waiting for area");
                        dump_stack();
                        return -ETIMEDOUT;
                }
                return -EINPROGRESS;
        }
        /* we own the area, do what we're here to do */
        if (pd->is_write)
                regmap_bulk_write(cd->regmap, pd->addr, pd->buf,
                                  pd->count);
        else
                regmap_bulk_read(cd->regmap, pd->addr, pd->buf,
                                 pd->count);
        /* ask to release the area, must use unlocked release */
        ind_ap &= ~IND_AP_ABITS;
        ind_ap |= pd->flags;
        ret = write_ind_ap(cd->regmap, ind_ap);
        if (ret)
                return ret;
        t->task_fn = task_fn_area_3;
        return -EINPROGRESS;
}

static int task_fn_area(struct anybuss_host *cd, struct ab_task *t)
{
        struct area_priv *pd = &t->area_pd;
        unsigned int ind_ap;
        int ret;

        if (!cd->power_on)
                return -EIO;
        regmap_read(cd->regmap, REG_IND_AP, &ind_ap);
        /* ask to take the area */
        ind_ap &= ~IND_AP_ABITS;
        ind_ap |= pd->flags | IND_AP_ACTION | IND_AP_LOCK;
        ret = write_ind_ap(cd->regmap, ind_ap);
        if (ret)
                return ret;
        t->task_fn = task_fn_area_2;
        return -EINPROGRESS;
}

static struct ab_task *
create_area_reader(struct kmem_cache *qcache, u16 flags, u16 addr,
                   size_t count)
{
        struct ab_task *t;
        struct area_priv *ap;

        t = ab_task_create_get(qcache, task_fn_area);
        if (!t)
                return NULL;
        ap = &t->area_pd;
        ap->flags = flags;
        ap->addr = addr;
        ap->is_write = false;
        ap->count = count;
        return t;
}

static struct ab_task *
create_area_writer(struct kmem_cache *qcache, u16 flags, u16 addr,
                   const void *buf, size_t count)
{
        struct ab_task *t;
        struct area_priv *ap;

        t = ab_task_create_get(qcache, task_fn_area);
        if (!t)
                return NULL;
        ap = &t->area_pd;
        ap->flags = flags;
        ap->addr = addr;
        ap->is_write = true;
        ap->count = count;
        memcpy(ap->buf, buf, count);
        return t;
}

static struct ab_task *
create_area_user_writer(struct kmem_cache *qcache, u16 flags, u16 addr,
                        const void __user *buf, size_t count)
{
        struct ab_task *t;
        struct area_priv *ap;

        t = ab_task_create_get(qcache, task_fn_area);
        if (!t)
                return ERR_PTR(-ENOMEM);
        ap = &t->area_pd;
        ap->flags = flags;
        ap->addr = addr;
        ap->is_write = true;
        ap->count = count;
        if (copy_from_user(ap->buf, buf, count)) {
                ab_task_put(t);
                return ERR_PTR(-EFAULT);
        }
        return t;
}

static bool area_range_ok(u16 addr, size_t count, u16 area_start,
                          size_t area_sz)
{
        u16 area_end_ex = area_start + area_sz;
        u16 addr_end_ex;

        if (addr < area_start)
                return false;
        if (addr >= area_end_ex)
                return false;
        addr_end_ex = addr + count;
        if (addr_end_ex > area_end_ex)
                return false;
        return true;
}

/* -------------------------- mailbox tasks ----------------------- */

static int task_fn_mbox_2(struct anybuss_host *cd, struct ab_task *t)
{
        struct mbox_priv *pd = &t->mbox_pd;
        unsigned int ind_ap;

        if (!cd->power_on)
                return -EIO;
        regmap_read(cd->regmap, REG_IND_AP, &ind_ap);
        if (((atomic_read(&cd->ind_ab) ^ ind_ap) & IND_AX_MOUT) == 0) {
                /* output message not here */
                if (time_after(jiffies, t->start_jiffies + TIMEOUT))
                        return -ETIMEDOUT;
                return -EINPROGRESS;
        }
        /* grab the returned header and msg */
        regmap_bulk_read(cd->regmap, MBOX_OUT_AREA, &pd->hdr,
                         sizeof(pd->hdr));
        regmap_bulk_read(cd->regmap, MBOX_OUT_AREA + sizeof(pd->hdr),
                         pd->msg, pd->msg_in_sz);
        /* tell anybus we've consumed the message */
        ind_ap ^= IND_AX_MOUT;
        return write_ind_ap(cd->regmap, ind_ap);
}

static int task_fn_mbox(struct anybuss_host *cd, struct ab_task *t)
{
        struct mbox_priv *pd = &t->mbox_pd;
        unsigned int ind_ap;
        int ret;

        if (!cd->power_on)
                return -EIO;
        regmap_read(cd->regmap, REG_IND_AP, &ind_ap);
        if ((atomic_read(&cd->ind_ab) ^ ind_ap) & IND_AX_MIN) {
                /* mbox input area busy */
                if (time_after(jiffies, t->start_jiffies + TIMEOUT))
                        return -ETIMEDOUT;
                return -EINPROGRESS;
        }
        /* write the header and msg to input area */
        regmap_bulk_write(cd->regmap, MBOX_IN_AREA, &pd->hdr,
                          sizeof(pd->hdr));
        regmap_bulk_write(cd->regmap, MBOX_IN_AREA + sizeof(pd->hdr),
                          pd->msg, pd->msg_out_sz);
        /* tell anybus we gave it a message */
        ind_ap ^= IND_AX_MIN;
        ret = write_ind_ap(cd->regmap, ind_ap);
        if (ret)
                return ret;
        t->start_jiffies = jiffies;
        t->task_fn = task_fn_mbox_2;
        return -EINPROGRESS;
}

static void log_invalid_other(struct device *dev,
                              struct anybus_mbox_hdr *hdr)
{
        size_t ext_offs = ARRAY_SIZE(hdr->extended) - 1;
        u16 code = be16_to_cpu(hdr->extended[ext_offs]);

        dev_err(dev, "   Invalid other: [0x%02X]", code);
}

static const char * const EMSGS[] = {
        "Invalid Message ID",
        "Invalid Message Type",
        "Invalid Command",
        "Invalid Data Size",
        "Message Header Malformed (offset 008h)",
        "Message Header Malformed (offset 00Ah)",
        "Message Header Malformed (offset 00Ch - 00Dh)",
        "Invalid Address",
        "Invalid Response",
        "Flash Config Error",
};

static int mbox_cmd_err(struct device *dev, struct mbox_priv *mpriv)
{
        int i;
        u8 ecode;
        struct anybus_mbox_hdr *hdr = &mpriv->hdr;
        u16 info = be16_to_cpu(hdr->info);
        u8 *phdr = (u8 *)hdr;
        u8 *pmsg = mpriv->msg;

        if (!(info & 0x8000))
                return 0;
        ecode = (info >> 8) & 0x0F;
        dev_err(dev, "mailbox command failed:");
        if (ecode == 0x0F)
                log_invalid_other(dev, hdr);
        else if (ecode < ARRAY_SIZE(EMSGS))
                dev_err(dev, "   Error code: %s (0x%02X)",
                        EMSGS[ecode], ecode);
        else
                dev_err(dev, "   Error code: 0x%02X\n", ecode);
        dev_err(dev, "Failed command:");
        dev_err(dev, "Message Header:");
        for (i = 0; i < sizeof(mpriv->hdr); i += 2)
                dev_err(dev, "%02X%02X", phdr[i], phdr[i + 1]);
        dev_err(dev, "Message Data:");
        for (i = 0; i < mpriv->msg_in_sz; i += 2)
                dev_err(dev, "%02X%02X", pmsg[i], pmsg[i + 1]);
        dev_err(dev, "Stack dump:");
        dump_stack();
        return -EIO;
}

static int _anybus_mbox_cmd(struct anybuss_host *cd,
                            u16 cmd_num, bool is_fb_cmd,
                                const void *msg_out, size_t msg_out_sz,
                                void *msg_in, size_t msg_in_sz,
                                const void *ext, size_t ext_sz)
{
        struct ab_task *t;
        struct mbox_priv *pd;
        struct anybus_mbox_hdr *h;
        size_t msg_sz = max(msg_in_sz, msg_out_sz);
        u16 info;
        int err;

        if (msg_sz > MAX_MBOX_MSG_SZ)
                return -EINVAL;
        if (ext && ext_sz > sizeof(h->extended))
                return -EINVAL;
        t = ab_task_create_get(cd->qcache, task_fn_mbox);
        if (!t)
                return -ENOMEM;
        pd = &t->mbox_pd;
        h = &pd->hdr;
        info = is_fb_cmd ? INFO_TYPE_FB : INFO_TYPE_APP;
        /*
         * prevent uninitialized memory in the header from being sent
         * across the anybus
         */
        memset(h, 0, sizeof(*h));
        h->info = cpu_to_be16(info | INFO_COMMAND);
        h->cmd_num = cpu_to_be16(cmd_num);
        h->data_size = cpu_to_be16(msg_out_sz);
        h->frame_count = cpu_to_be16(1);
        h->frame_num = cpu_to_be16(1);
        h->offset_high = cpu_to_be16(0);
        h->offset_low = cpu_to_be16(0);
        if (ext)
                memcpy(h->extended, ext, ext_sz);
        memcpy(pd->msg, msg_out, msg_out_sz);
        pd->msg_out_sz = msg_out_sz;
        pd->msg_in_sz = msg_in_sz;
        err = ab_task_enqueue_wait(t, cd->powerq, &cd->qlock, &cd->wq);
        if (err)
                goto out;
        /*
         * mailbox mechanism worked ok, but maybe the mbox response
         * contains an error ?
         */
        err = mbox_cmd_err(cd->dev, pd);
        if (err)
                goto out;
        memcpy(msg_in, pd->msg, msg_in_sz);
out:
        ab_task_put(t);
        return err;
}

/* ------------------------ anybus queues ------------------------ */

static void process_q(struct anybuss_host *cd, struct kfifo *q)
{
        struct ab_task *t;
        int ret;

        ret = kfifo_out_peek(q, &t, sizeof(t));
        if (!ret)
                return;
        t->result = t->task_fn(cd, t);
        if (t->result != -EINPROGRESS)
                ab_task_dequeue_finish_put(q, cd);
}

static bool qs_have_work(struct kfifo *qs, size_t num)
{
        size_t i;
        struct ab_task *t;
        int ret;

        for (i = 0; i < num; i++, qs++) {
                ret = kfifo_out_peek(qs, &t, sizeof(t));
                if (ret && (t->result != -EINPROGRESS))
                        return true;
        }
        return false;
}

static void process_qs(struct anybuss_host *cd)
{
        size_t i;
        struct kfifo *qs = cd->qs;
        size_t nqs = ARRAY_SIZE(cd->qs);

        for (i = 0; i < nqs; i++, qs++)
                process_q(cd, qs);
}

static void softint_ack(struct anybuss_host *cd)
{
        unsigned int ind_ap;

        cd->softint_pending = false;
        if (!cd->power_on)
                return;
        regmap_read(cd->regmap, REG_IND_AP, &ind_ap);
        ind_ap &= ~IND_AX_EVNT;
        ind_ap |= atomic_read(&cd->ind_ab) & IND_AX_EVNT;
        write_ind_ap(cd->regmap, ind_ap);
}

static void process_softint(struct anybuss_host *cd)
{
        struct anybuss_client *client = cd->client;
        static const u8 zero;
        int ret;
        unsigned int ind_ap, ev;
        struct ab_task *t;

        if (!cd->power_on)
                return;
        if (cd->softint_pending)
                return;
        regmap_read(cd->regmap, REG_IND_AP, &ind_ap);
        if (!((atomic_read(&cd->ind_ab) ^ ind_ap) & IND_AX_EVNT))
                return;
        /* process software interrupt */
        regmap_read(cd->regmap, REG_EVENT_CAUSE, &ev);
        if (ev & EVENT_CAUSE_FBON) {
                if (client->on_online_changed)
                        client->on_online_changed(client, true);
                dev_dbg(cd->dev, "Fieldbus ON");
        }
        if (ev & EVENT_CAUSE_FBOF) {
                if (client->on_online_changed)
                        client->on_online_changed(client, false);
                dev_dbg(cd->dev, "Fieldbus OFF");
        }
        if (ev & EVENT_CAUSE_DC) {
                if (client->on_area_updated)
                        client->on_area_updated(client);
                dev_dbg(cd->dev, "Fieldbus data changed");
        }
        /*
         * reset the event cause bits.
         * this must be done while owning the fbctrl area, so we'll
         * enqueue a task to do that.
         */
        t = create_area_writer(cd->qcache, IND_AX_FBCTRL,
                               REG_EVENT_CAUSE, &zero, sizeof(zero));
        if (!t) {
                ret = -ENOMEM;
                goto out;
        }
        t->done_fn = softint_ack;
        ret = ab_task_enqueue(t, cd->powerq, &cd->qlock, &cd->wq);
        ab_task_put(t);
        cd->softint_pending = true;
out:
        WARN_ON(ret);
        if (ret)
                softint_ack(cd);
}

static int qthread_fn(void *data)
{
        struct anybuss_host *cd = data;
        struct kfifo *qs = cd->qs;
        size_t nqs = ARRAY_SIZE(cd->qs);
        unsigned int ind_ab;

        /*
         * this kernel thread has exclusive access to the anybus's memory.
         * only exception: the IND_AB register, which is accessed exclusively
         * by the interrupt service routine (ISR). This thread must not touch
         * the IND_AB register, but it does require access to its value.
         *
         * the interrupt service routine stores the register's value in
         * cd->ind_ab (an atomic_t), where we may safely access it, with the
         * understanding that it can be modified by the ISR at any time.
         */

        while (!kthread_should_stop()) {
                /*
                 * make a local copy of IND_AB, so we can go around the loop
                 * again in case it changed while processing queues and softint.
                 */
                ind_ab = atomic_read(&cd->ind_ab);
                process_qs(cd);
                process_softint(cd);
                wait_event_timeout(cd->wq,
                                   (atomic_read(&cd->ind_ab) != ind_ab) ||
                                qs_have_work(qs, nqs) ||
                                kthread_should_stop(),
                        HZ);
                /*
                 * time out so even 'stuck' tasks will run eventually,
                 * and can time out.
                 */
        }

        return 0;
}

/* ------------------------ anybus exports ------------------------ */

int anybuss_start_init(struct anybuss_client *client,
                       const struct anybuss_memcfg *cfg)
{
        int ret;
        u16 op_mode;
        struct anybuss_host *cd = client->host;
        struct msg_anybus_init msg = {
                .input_io_len = cpu_to_be16(cfg->input_io),
                .input_dpram_len = cpu_to_be16(cfg->input_dpram),
                .input_total_len = cpu_to_be16(cfg->input_total),
                .output_io_len = cpu_to_be16(cfg->output_io),
                .output_dpram_len = cpu_to_be16(cfg->output_dpram),
                .output_total_len = cpu_to_be16(cfg->output_total),
                .notif_config = cpu_to_be16(0x000F),
                .wd_val = cpu_to_be16(0),
        };

        switch (cfg->offl_mode) {
        case FIELDBUS_DEV_OFFL_MODE_CLEAR:
                op_mode = 0;
                break;
        case FIELDBUS_DEV_OFFL_MODE_FREEZE:
                op_mode = OP_MODE_FBFC;
                break;
        case FIELDBUS_DEV_OFFL_MODE_SET:
                op_mode = OP_MODE_FBS;
                break;
        default:
                return -EINVAL;
        }
        msg.op_mode = cpu_to_be16(op_mode | OP_MODE_CD);
        ret = _anybus_mbox_cmd(cd, CMD_START_INIT, false, NULL, 0,
                               NULL, 0, NULL, 0);
        if (ret)
                return ret;
        return _anybus_mbox_cmd(cd, CMD_ANYBUS_INIT, false,
                        &msg, sizeof(msg), NULL, 0, NULL, 0);
}
EXPORT_SYMBOL_GPL(anybuss_start_init);

int anybuss_finish_init(struct anybuss_client *client)
{
        struct anybuss_host *cd = client->host;

        return _anybus_mbox_cmd(cd, CMD_END_INIT, false, NULL, 0,
                                        NULL, 0, NULL, 0);
}
EXPORT_SYMBOL_GPL(anybuss_finish_init);

int anybuss_read_fbctrl(struct anybuss_client *client, u16 addr,
                        void *buf, size_t count)
{
        struct anybuss_host *cd = client->host;
        struct ab_task *t;
        int ret;

        if (count == 0)
                return 0;
        if (!area_range_ok(addr, count, FBCTRL_AREA,
                           MAX_FBCTRL_AREA_SZ))
                return -EFAULT;
        t = create_area_reader(cd->qcache, IND_AX_FBCTRL, addr, count);
        if (!t)
                return -ENOMEM;
        ret = ab_task_enqueue_wait(t, cd->powerq, &cd->qlock, &cd->wq);
        if (ret)
                goto out;
        memcpy(buf, t->area_pd.buf, count);
out:
        ab_task_put(t);
        return ret;
}
EXPORT_SYMBOL_GPL(anybuss_read_fbctrl);

int anybuss_write_input(struct anybuss_client *client,
                        const char __user *buf, size_t size,
                                loff_t *offset)
{
        ssize_t len = min_t(loff_t, MAX_DATA_AREA_SZ - *offset, size);
        struct anybuss_host *cd = client->host;
        struct ab_task *t;
        int ret;

        if (len <= 0)
                return 0;
        t = create_area_user_writer(cd->qcache, IND_AX_IN,
                                    DATA_IN_AREA + *offset, buf, len);
        if (IS_ERR(t))
                return PTR_ERR(t);
        ret = ab_task_enqueue_wait(t, cd->powerq, &cd->qlock, &cd->wq);
        ab_task_put(t);
        if (ret)
                return ret;
        /* success */
        *offset += len;
        return len;
}
EXPORT_SYMBOL_GPL(anybuss_write_input);

int anybuss_read_output(struct anybuss_client *client,
                        char __user *buf, size_t size,
                                loff_t *offset)
{
        ssize_t len = min_t(loff_t, MAX_DATA_AREA_SZ - *offset, size);
        struct anybuss_host *cd = client->host;
        struct ab_task *t;
        int ret;

        if (len <= 0)
                return 0;
        t = create_area_reader(cd->qcache, IND_AX_OUT,
                               DATA_OUT_AREA + *offset, len);
        if (!t)
                return -ENOMEM;
        ret = ab_task_enqueue_wait(t, cd->powerq, &cd->qlock, &cd->wq);
        if (ret)
                goto out;
        if (copy_to_user(buf, t->area_pd.buf, len))
                ret = -EFAULT;
out:
        ab_task_put(t);
        if (ret)
                return ret;
        /* success */
        *offset += len;
        return len;
}
EXPORT_SYMBOL_GPL(anybuss_read_output);

int anybuss_send_msg(struct anybuss_client *client, u16 cmd_num,
                     const void *buf, size_t count)
{
        struct anybuss_host *cd = client->host;

        return _anybus_mbox_cmd(cd, cmd_num, true, buf, count, NULL, 0,
                                        NULL, 0);
}
EXPORT_SYMBOL_GPL(anybuss_send_msg);

int anybuss_send_ext(struct anybuss_client *client, u16 cmd_num,
                     const void *buf, size_t count)
{
        struct anybuss_host *cd = client->host;

        return _anybus_mbox_cmd(cd, cmd_num, true, NULL, 0, NULL, 0,
                                        buf, count);
}
EXPORT_SYMBOL_GPL(anybuss_send_ext);

int anybuss_recv_msg(struct anybuss_client *client, u16 cmd_num,
                     void *buf, size_t count)
{
        struct anybuss_host *cd = client->host;

        return _anybus_mbox_cmd(cd, cmd_num, true, NULL, 0, buf, count,
                                        NULL, 0);
}
EXPORT_SYMBOL_GPL(anybuss_recv_msg);

/* ------------------------ bus functions ------------------------ */

static int anybus_bus_match(struct device *dev,
                            struct device_driver *drv)
{
        struct anybuss_client_driver *adrv =
                to_anybuss_client_driver(drv);
        struct anybuss_client *adev =
                to_anybuss_client(dev);

        return adrv->anybus_id == be16_to_cpu(adev->anybus_id);
}

static int anybus_bus_probe(struct device *dev)
{
        struct anybuss_client_driver *adrv =
                to_anybuss_client_driver(dev->driver);
        struct anybuss_client *adev =
                to_anybuss_client(dev);

        return adrv->probe(adev);
}

static void anybus_bus_remove(struct device *dev)
{
        struct anybuss_client_driver *adrv =
                to_anybuss_client_driver(dev->driver);

        if (adrv->remove)
                adrv->remove(to_anybuss_client(dev));
}

static struct bus_type anybus_bus = {
        .name           = "anybuss",
        .match          = anybus_bus_match,
        .probe          = anybus_bus_probe,
        .remove         = anybus_bus_remove,
};

int anybuss_client_driver_register(struct anybuss_client_driver *drv)
{
        if (!drv->probe)
                return -ENODEV;

        drv->driver.bus = &anybus_bus;
        return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(anybuss_client_driver_register);

void anybuss_client_driver_unregister(struct anybuss_client_driver *drv)
{
        return driver_unregister(&drv->driver);
}
EXPORT_SYMBOL_GPL(anybuss_client_driver_unregister);

static void client_device_release(struct device *dev)
{
        kfree(to_anybuss_client(dev));
}

static int taskq_alloc(struct device *dev, struct kfifo *q)
{
        void *buf;
        size_t size = 64 * sizeof(struct ab_task *);

        buf = devm_kzalloc(dev, size, GFP_KERNEL);
        if (!buf)
                return -EIO;
        return kfifo_init(q, buf, size);
}

static int anybus_of_get_host_idx(struct device_node *np)
{
        const __be32 *host_idx;

        host_idx = of_get_address(np, 0, NULL, NULL);
        if (!host_idx)
                return -ENOENT;
        return __be32_to_cpu(*host_idx);
}

static struct device_node *
anybus_of_find_child_device(struct device *dev, int host_idx)
{
        struct device_node *node;

        if (!dev || !dev->of_node)
                return NULL;
        for_each_child_of_node(dev->of_node, node) {
                if (anybus_of_get_host_idx(node) == host_idx)
                        return node;
        }
        return NULL;
}

struct anybuss_host * __must_check
anybuss_host_common_probe(struct device *dev,
                          const struct anybuss_ops *ops)
{
        int ret, i;
        u8 val[4];
        __be16 fieldbus_type;
        struct anybuss_host *cd;

        cd = devm_kzalloc(dev, sizeof(*cd), GFP_KERNEL);
        if (!cd)
                return ERR_PTR(-ENOMEM);
        cd->dev = dev;
        cd->host_idx = ops->host_idx;
        init_completion(&cd->card_boot);
        init_waitqueue_head(&cd->wq);
        for (i = 0; i < ARRAY_SIZE(cd->qs); i++) {
                ret = taskq_alloc(dev, &cd->qs[i]);
                if (ret)
                        return ERR_PTR(ret);
        }
        if (WARN_ON(ARRAY_SIZE(cd->qs) < 3))
                return ERR_PTR(-EINVAL);
        cd->powerq = &cd->qs[0];
        cd->mboxq = &cd->qs[1];
        cd->areaq = &cd->qs[2];
        cd->reset = ops->reset;
        if (!cd->reset)
                return ERR_PTR(-EINVAL);
        cd->regmap = ops->regmap;
        if (!cd->regmap)
                return ERR_PTR(-EINVAL);
        spin_lock_init(&cd->qlock);
        cd->qcache = kmem_cache_create(dev_name(dev),
                                       sizeof(struct ab_task), 0, 0, NULL);
        if (!cd->qcache)
                return ERR_PTR(-ENOMEM);
        cd->irq = ops->irq;
        if (cd->irq <= 0) {
                ret = -EINVAL;
                goto err_qcache;
        }
        /*
         * use a dpram test to check if a card is present, this is only
         * possible while in reset.
         */
        reset_assert(cd);
        if (test_dpram(cd->regmap)) {
                dev_err(dev, "no Anybus-S card in slot");
                ret = -ENODEV;
                goto err_qcache;
        }
        ret = devm_request_threaded_irq(dev, cd->irq, NULL, irq_handler,
                                        IRQF_ONESHOT, dev_name(dev), cd);
        if (ret) {
                dev_err(dev, "could not request irq");
                goto err_qcache;
        }
        /*
         * startup sequence:
         *   perform dummy IND_AB read to prevent false 'init done' irq
         *     (already done by test_dpram() above)
         *   release reset
         *   wait for first interrupt
         *   interrupt came in: ready to go !
         */
        reset_deassert(cd);
        if (!wait_for_completion_timeout(&cd->card_boot, TIMEOUT)) {
                ret = -ETIMEDOUT;
                goto err_reset;
        }
        /*
         * according to the anybus docs, we're allowed to read these
         * without handshaking / reserving the area
         */
        dev_info(dev, "Anybus-S card detected");
        regmap_bulk_read(cd->regmap, REG_BOOTLOADER_V, val, 2);
        dev_info(dev, "Bootloader version: %02X%02X",
                 val[0], val[1]);
        regmap_bulk_read(cd->regmap, REG_API_V, val, 2);
        dev_info(dev, "API version: %02X%02X", val[0], val[1]);
        regmap_bulk_read(cd->regmap, REG_FIELDBUS_V, val, 2);
        dev_info(dev, "Fieldbus version: %02X%02X", val[0], val[1]);
        regmap_bulk_read(cd->regmap, REG_SERIAL_NO, val, 4);
        dev_info(dev, "Serial number: %02X%02X%02X%02X",
                 val[0], val[1], val[2], val[3]);
        add_device_randomness(&val, 4);
        regmap_bulk_read(cd->regmap, REG_FIELDBUS_TYPE, &fieldbus_type,
                         sizeof(fieldbus_type));
        dev_info(dev, "Fieldbus type: %04X", be16_to_cpu(fieldbus_type));
        regmap_bulk_read(cd->regmap, REG_MODULE_SW_V, val, 2);
        dev_info(dev, "Module SW version: %02X%02X",
                 val[0], val[1]);
        /* put card back reset until a client driver releases it */
        disable_irq(cd->irq);
        reset_assert(cd);
        atomic_set(&cd->ind_ab, IND_AB_UPDATED);
        /* fire up the queue thread */
        cd->qthread = kthread_run(qthread_fn, cd, dev_name(dev));
        if (IS_ERR(cd->qthread)) {
                dev_err(dev, "could not create kthread");
                ret = PTR_ERR(cd->qthread);
                goto err_reset;
        }
        /*
         * now advertise that we've detected a client device (card).
         * the bus infrastructure will match it to a client driver.
         */
        cd->client = kzalloc(sizeof(*cd->client), GFP_KERNEL);
        if (!cd->client) {
                ret = -ENOMEM;
                goto err_kthread;
        }
        cd->client->anybus_id = fieldbus_type;
        cd->client->host = cd;
        cd->client->dev.bus = &anybus_bus;
        cd->client->dev.parent = dev;
        cd->client->dev.release = client_device_release;
        cd->client->dev.of_node =
                anybus_of_find_child_device(dev, cd->host_idx);
        dev_set_name(&cd->client->dev, "anybuss.card%d", cd->host_idx);
        ret = device_register(&cd->client->dev);
        if (ret)
                goto err_device;
        return cd;
err_device:
        device_unregister(&cd->client->dev);
err_kthread:
        kthread_stop(cd->qthread);
err_reset:
        reset_assert(cd);
err_qcache:
        kmem_cache_destroy(cd->qcache);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(anybuss_host_common_probe);

void anybuss_host_common_remove(struct anybuss_host *host)
{
        struct anybuss_host *cd = host;

        device_unregister(&cd->client->dev);
        kthread_stop(cd->qthread);
        reset_assert(cd);
        kmem_cache_destroy(cd->qcache);
}
EXPORT_SYMBOL_GPL(anybuss_host_common_remove);

static void host_release(void *res)
{
        anybuss_host_common_remove(res);
}

struct anybuss_host * __must_check
devm_anybuss_host_common_probe(struct device *dev,
                               const struct anybuss_ops *ops)
{
        struct anybuss_host *host;
        int ret;

        host = anybuss_host_common_probe(dev, ops);
        if (IS_ERR(host))
                return host;

        ret = devm_add_action_or_reset(dev, host_release, host);
        if (ret)
                return ERR_PTR(ret);

        return host;
}
EXPORT_SYMBOL_GPL(devm_anybuss_host_common_probe);

static int __init anybus_init(void)
{
        int ret;

        ret = bus_register(&anybus_bus);
        if (ret)
                pr_err("could not register Anybus-S bus: %d\n", ret);
        return ret;
}
module_init(anybus_init);

static void __exit anybus_exit(void)
{
        bus_unregister(&anybus_bus);
}
module_exit(anybus_exit);

MODULE_DESCRIPTION("HMS Anybus-S Host Driver");
MODULE_AUTHOR("Sven Van Asbroeck <TheSven73@gmail.com>");
MODULE_LICENSE("GPL v2");