/*
 * Copyright (c) 2015, Sony Mobile Communications AB.
 * Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only 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.
 */

#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/soc/qcom/smem.h>
#include <linux/soc/qcom/smem_state.h>
#include <linux/spinlock.h>

/*
 * The Shared Memory Point to Point (SMP2P) protocol facilitates communication
 * of a single 32-bit value between two processors.  Each value has a single
 * writer (the local side) and a single reader (the remote side). Values are
 * uniquely identified in the system by the directed edge (local processor ID
 * to remote processor ID) and a string identifier.
 *
 * Each processor is responsible for creating the outgoing SMEM items and each
 * item is writable by the local processor and readable by the remote
 * processor.  By using two separate SMEM items that are single-reader and
 * single-writer, SMP2P does not require any remote locking mechanisms.
 *
 * The driver uses the Linux GPIO and interrupt framework to expose a virtual
 * GPIO for each outbound entry and a virtual interrupt controller for each
 * inbound entry.
 */

#define SMP2P_MAX_ENTRY 16
#define SMP2P_MAX_ENTRY_NAME 16

#define SMP2P_FEATURE_SSR_ACK 0x1

#define SMP2P_MAGIC 0x504d5324

/**
 * struct smp2p_smem_item - in memory communication structure
 * @magic:              magic number
 * @version:            version - must be 1
 * @features:           features flag - currently unused
 * @local_pid:          processor id of sending end
 * @remote_pid:         processor id of receiving end
 * @total_entries:      number of entries - always SMP2P_MAX_ENTRY
 * @valid_entries:      number of allocated entries
 * @flags:
 * @entries:            individual communication entries
 *     @name:           name of the entry
 *     @value:          content of the entry
 */
struct smp2p_smem_item {
        u32 magic;
        u8 version;
        unsigned features:24;
        u16 local_pid;
        u16 remote_pid;
        u16 total_entries;
        u16 valid_entries;
        u32 flags;

        struct {
                u8 name[SMP2P_MAX_ENTRY_NAME];
                u32 value;
        } entries[SMP2P_MAX_ENTRY];
} __packed;

/**
 * struct smp2p_entry - driver context matching one entry
 * @node:       list entry to keep track of allocated entries
 * @smp2p:      reference to the device driver context
 * @name:       name of the entry, to match against smp2p_smem_item
 * @value:      pointer to smp2p_smem_item entry value
 * @last_value: last handled value
 * @domain:     irq_domain for inbound entries
 * @irq_enabled:bitmap to track enabled irq bits
 * @irq_rising: bitmap to mark irq bits for rising detection
 * @irq_falling:bitmap to mark irq bits for falling detection
 * @state:      smem state handle
 * @lock:       spinlock to protect read-modify-write of the value
 */
struct smp2p_entry {
        struct list_head node;
        struct qcom_smp2p *smp2p;

        const char *name;
        u32 *value;
        u32 last_value;

        struct irq_domain *domain;
        DECLARE_BITMAP(irq_enabled, 32);
        DECLARE_BITMAP(irq_rising, 32);
        DECLARE_BITMAP(irq_falling, 32);

        struct qcom_smem_state *state;

        spinlock_t lock;
};

#define SMP2P_INBOUND   0
#define SMP2P_OUTBOUND  1

/**
 * struct qcom_smp2p - device driver context
 * @dev:        device driver handle
 * @in:         pointer to the inbound smem item
 * @smem_items: ids of the two smem items
 * @valid_entries: already scanned inbound entries
 * @local_pid:  processor id of the inbound edge
 * @remote_pid: processor id of the outbound edge
 * @ipc_regmap: regmap for the outbound ipc
 * @ipc_offset: offset within the regmap
 * @ipc_bit:    bit in regmap@offset to kick to signal remote processor
 * @inbound:    list of inbound entries
 * @outbound:   list of outbound entries
 */
struct qcom_smp2p {
        struct device *dev;

        struct smp2p_smem_item *in;
        struct smp2p_smem_item *out;

        unsigned smem_items[SMP2P_OUTBOUND + 1];

        unsigned valid_entries;

        unsigned local_pid;
        unsigned remote_pid;

        struct regmap *ipc_regmap;
        int ipc_offset;
        int ipc_bit;

        struct list_head inbound;
        struct list_head outbound;
};

static void qcom_smp2p_kick(struct qcom_smp2p *smp2p)
{
        /* Make sure any updated data is written before the kick */
        wmb();
        regmap_write(smp2p->ipc_regmap, smp2p->ipc_offset, BIT(smp2p->ipc_bit));
}

/**
 * qcom_smp2p_intr() - interrupt handler for incoming notifications
 * @irq:        unused
 * @data:       smp2p driver context
 *
 * Handle notifications from the remote side to handle newly allocated entries
 * or any changes to the state bits of existing entries.
 */
static irqreturn_t qcom_smp2p_intr(int irq, void *data)
{
        struct smp2p_smem_item *in;
        struct smp2p_entry *entry;
        struct qcom_smp2p *smp2p = data;
        unsigned smem_id = smp2p->smem_items[SMP2P_INBOUND];
        unsigned pid = smp2p->remote_pid;
        size_t size;
        int irq_pin;
        u32 status;
        char buf[SMP2P_MAX_ENTRY_NAME];
        u32 val;
        int i;

        in = smp2p->in;

        /* Acquire smem item, if not already found */
        if (!in) {
                in = qcom_smem_get(pid, smem_id, &size);
                if (IS_ERR(in)) {
                        dev_err(smp2p->dev,
                                "Unable to acquire remote smp2p item\n");
                        return IRQ_HANDLED;
                }

                smp2p->in = in;
        }

        /* Match newly created entries */
        for (i = smp2p->valid_entries; i < in->valid_entries; i++) {
                list_for_each_entry(entry, &smp2p->inbound, node) {
                        memcpy(buf, in->entries[i].name, sizeof(buf));
                        if (!strcmp(buf, entry->name)) {
                                entry->value = &in->entries[i].value;
                                break;
                        }
                }
        }
        smp2p->valid_entries = i;

        /* Fire interrupts based on any value changes */
        list_for_each_entry(entry, &smp2p->inbound, node) {
                /* Ignore entries not yet allocated by the remote side */
                if (!entry->value)
                        continue;

                val = readl(entry->value);

                status = val ^ entry->last_value;
                entry->last_value = val;

                /* No changes of this entry? */
                if (!status)
                        continue;

                for_each_set_bit(i, entry->irq_enabled, 32) {
                        if (!(status & BIT(i)))
                                continue;

                        if ((val & BIT(i) && test_bit(i, entry->irq_rising)) ||
                            (!(val & BIT(i)) && test_bit(i, entry->irq_falling))) {
                                irq_pin = irq_find_mapping(entry->domain, i);
                                handle_nested_irq(irq_pin);
                        }
                }
        }

        return IRQ_HANDLED;
}

static void smp2p_mask_irq(struct irq_data *irqd)
{
        struct smp2p_entry *entry = irq_data_get_irq_chip_data(irqd);
        irq_hw_number_t irq = irqd_to_hwirq(irqd);

        clear_bit(irq, entry->irq_enabled);
}

static void smp2p_unmask_irq(struct irq_data *irqd)
{
        struct smp2p_entry *entry = irq_data_get_irq_chip_data(irqd);
        irq_hw_number_t irq = irqd_to_hwirq(irqd);

        set_bit(irq, entry->irq_enabled);
}

static int smp2p_set_irq_type(struct irq_data *irqd, unsigned int type)
{
        struct smp2p_entry *entry = irq_data_get_irq_chip_data(irqd);
        irq_hw_number_t irq = irqd_to_hwirq(irqd);

        if (!(type & IRQ_TYPE_EDGE_BOTH))
                return -EINVAL;

        if (type & IRQ_TYPE_EDGE_RISING)
                set_bit(irq, entry->irq_rising);
        else
                clear_bit(irq, entry->irq_rising);

        if (type & IRQ_TYPE_EDGE_FALLING)
                set_bit(irq, entry->irq_falling);
        else
                clear_bit(irq, entry->irq_falling);

        return 0;
}

static struct irq_chip smp2p_irq_chip = {
        .name           = "smp2p",
        .irq_mask       = smp2p_mask_irq,
        .irq_unmask     = smp2p_unmask_irq,
        .irq_set_type   = smp2p_set_irq_type,
};

static int smp2p_irq_map(struct irq_domain *d,
                         unsigned int irq,
                         irq_hw_number_t hw)
{
        struct smp2p_entry *entry = d->host_data;

        irq_set_chip_and_handler(irq, &smp2p_irq_chip, handle_level_irq);
        irq_set_chip_data(irq, entry);
        irq_set_nested_thread(irq, 1);
        irq_set_noprobe(irq);

        return 0;
}

static const struct irq_domain_ops smp2p_irq_ops = {
        .map = smp2p_irq_map,
        .xlate = irq_domain_xlate_twocell,
};

static int qcom_smp2p_inbound_entry(struct qcom_smp2p *smp2p,
                                    struct smp2p_entry *entry,
                                    struct device_node *node)
{
        entry->domain = irq_domain_add_linear(node, 32, &smp2p_irq_ops, entry);
        if (!entry->domain) {
                dev_err(smp2p->dev, "failed to add irq_domain\n");
                return -ENOMEM;
        }

        return 0;
}

static int smp2p_update_bits(void *data, u32 mask, u32 value)
{
        struct smp2p_entry *entry = data;
        u32 orig;
        u32 val;

        spin_lock(&entry->lock);
        val = orig = readl(entry->value);
        val &= ~mask;
        val |= value;
        writel(val, entry->value);
        spin_unlock(&entry->lock);

        if (val != orig)
                qcom_smp2p_kick(entry->smp2p);

        return 0;
}

static const struct qcom_smem_state_ops smp2p_state_ops = {
        .update_bits = smp2p_update_bits,
};

static int qcom_smp2p_outbound_entry(struct qcom_smp2p *smp2p,
                                     struct smp2p_entry *entry,
                                     struct device_node *node)
{
        struct smp2p_smem_item *out = smp2p->out;
        char buf[SMP2P_MAX_ENTRY_NAME] = {};

        /* Allocate an entry from the smem item */
        strlcpy(buf, entry->name, SMP2P_MAX_ENTRY_NAME);
        memcpy(out->entries[out->valid_entries].name, buf, SMP2P_MAX_ENTRY_NAME);

        /* Make the logical entry reference the physical value */
        entry->value = &out->entries[out->valid_entries].value;

        out->valid_entries++;

        entry->state = qcom_smem_state_register(node, &smp2p_state_ops, entry);
        if (IS_ERR(entry->state)) {
                dev_err(smp2p->dev, "failed to register qcom_smem_state\n");
                return PTR_ERR(entry->state);
        }

        return 0;
}

static int qcom_smp2p_alloc_outbound_item(struct qcom_smp2p *smp2p)
{
        struct smp2p_smem_item *out;
        unsigned smem_id = smp2p->smem_items[SMP2P_OUTBOUND];
        unsigned pid = smp2p->remote_pid;
        int ret;

        ret = qcom_smem_alloc(pid, smem_id, sizeof(*out));
        if (ret < 0 && ret != -EEXIST) {
                if (ret != -EPROBE_DEFER)
                        dev_err(smp2p->dev,
                                "unable to allocate local smp2p item\n");
                return ret;
        }

        out = qcom_smem_get(pid, smem_id, NULL);
        if (IS_ERR(out)) {
                dev_err(smp2p->dev, "Unable to acquire local smp2p item\n");
                return PTR_ERR(out);
        }

        memset(out, 0, sizeof(*out));
        out->magic = SMP2P_MAGIC;
        out->local_pid = smp2p->local_pid;
        out->remote_pid = smp2p->remote_pid;
        out->total_entries = SMP2P_MAX_ENTRY;
        out->valid_entries = 0;

        /*
         * Make sure the rest of the header is written before we validate the
         * item by writing a valid version number.
         */
        wmb();
        out->version = 1;

        qcom_smp2p_kick(smp2p);

        smp2p->out = out;

        return 0;
}

static int smp2p_parse_ipc(struct qcom_smp2p *smp2p)
{
        struct device_node *syscon;
        struct device *dev = smp2p->dev;
        const char *key;
        int ret;

        syscon = of_parse_phandle(dev->of_node, "qcom,ipc", 0);
        if (!syscon) {
                dev_err(dev, "no qcom,ipc node\n");
                return -ENODEV;
        }

        smp2p->ipc_regmap = syscon_node_to_regmap(syscon);
        if (IS_ERR(smp2p->ipc_regmap))
                return PTR_ERR(smp2p->ipc_regmap);

        key = "qcom,ipc";
        ret = of_property_read_u32_index(dev->of_node, key, 1, &smp2p->ipc_offset);
        if (ret < 0) {
                dev_err(dev, "no offset in %s\n", key);
                return -EINVAL;
        }

        ret = of_property_read_u32_index(dev->of_node, key, 2, &smp2p->ipc_bit);
        if (ret < 0) {
                dev_err(dev, "no bit in %s\n", key);
                return -EINVAL;
        }

        return 0;
}

static int qcom_smp2p_probe(struct platform_device *pdev)
{
        struct smp2p_entry *entry;
        struct device_node *node;
        struct qcom_smp2p *smp2p;
        const char *key;
        int irq;
        int ret;

        smp2p = devm_kzalloc(&pdev->dev, sizeof(*smp2p), GFP_KERNEL);
        if (!smp2p)
                return -ENOMEM;

        smp2p->dev = &pdev->dev;
        INIT_LIST_HEAD(&smp2p->inbound);
        INIT_LIST_HEAD(&smp2p->outbound);

        platform_set_drvdata(pdev, smp2p);

        ret = smp2p_parse_ipc(smp2p);
        if (ret)
                return ret;

        key = "qcom,smem";
        ret = of_property_read_u32_array(pdev->dev.of_node, key,
                                         smp2p->smem_items, 2);
        if (ret)
                return ret;

        key = "qcom,local-pid";
        ret = of_property_read_u32(pdev->dev.of_node, key, &smp2p->local_pid);
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to read %s\n", key);
                return -EINVAL;
        }

        key = "qcom,remote-pid";
        ret = of_property_read_u32(pdev->dev.of_node, key, &smp2p->remote_pid);
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to read %s\n", key);
                return -EINVAL;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                dev_err(&pdev->dev, "unable to acquire smp2p interrupt\n");
                return irq;
        }

        ret = qcom_smp2p_alloc_outbound_item(smp2p);
        if (ret < 0)
                return ret;

        for_each_available_child_of_node(pdev->dev.of_node, node) {
                entry = devm_kzalloc(&pdev->dev, sizeof(*entry), GFP_KERNEL);
                if (!entry) {
                        ret = -ENOMEM;
                        goto unwind_interfaces;
                }

                entry->smp2p = smp2p;
                spin_lock_init(&entry->lock);

                ret = of_property_read_string(node, "qcom,entry-name", &entry->name);
                if (ret < 0)
                        goto unwind_interfaces;

                if (of_property_read_bool(node, "interrupt-controller")) {
                        ret = qcom_smp2p_inbound_entry(smp2p, entry, node);
                        if (ret < 0)
                                goto unwind_interfaces;

                        list_add(&entry->node, &smp2p->inbound);
                } else  {
                        ret = qcom_smp2p_outbound_entry(smp2p, entry, node);
                        if (ret < 0)
                                goto unwind_interfaces;

                        list_add(&entry->node, &smp2p->outbound);
                }
        }

        /* Kick the outgoing edge after allocating entries */
        qcom_smp2p_kick(smp2p);

        ret = devm_request_threaded_irq(&pdev->dev, irq,
                                        NULL, qcom_smp2p_intr,
                                        IRQF_ONESHOT,
                                        "smp2p", (void *)smp2p);
        if (ret) {
                dev_err(&pdev->dev, "failed to request interrupt\n");
                goto unwind_interfaces;
        }


        return 0;

unwind_interfaces:
        list_for_each_entry(entry, &smp2p->inbound, node)
                irq_domain_remove(entry->domain);

        list_for_each_entry(entry, &smp2p->outbound, node)
                qcom_smem_state_unregister(entry->state);

        smp2p->out->valid_entries = 0;

        return ret;
}

static int qcom_smp2p_remove(struct platform_device *pdev)
{
        struct qcom_smp2p *smp2p = platform_get_drvdata(pdev);
        struct smp2p_entry *entry;

        list_for_each_entry(entry, &smp2p->inbound, node)
                irq_domain_remove(entry->domain);

        list_for_each_entry(entry, &smp2p->outbound, node)
                qcom_smem_state_unregister(entry->state);

        smp2p->out->valid_entries = 0;

        return 0;
}

static const struct of_device_id qcom_smp2p_of_match[] = {
        { .compatible = "qcom,smp2p" },
        {}
};
MODULE_DEVICE_TABLE(of, qcom_smp2p_of_match);

static struct platform_driver qcom_smp2p_driver = {
        .probe = qcom_smp2p_probe,
        .remove = qcom_smp2p_remove,
        .driver  = {
                .name  = "qcom_smp2p",
                .of_match_table = qcom_smp2p_of_match,
        },
};
module_platform_driver(qcom_smp2p_driver);

MODULE_DESCRIPTION("Qualcomm Shared Memory Point to Point driver");
MODULE_LICENSE("GPL v2");