/*
 * Copyright (c) 2015, Sony Mobile Communications Inc.
 * 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/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/regmap.h>
#include <linux/soc/qcom/smem.h>
#include <linux/soc/qcom/smem_state.h>

/*
 * This driver implements the Qualcomm Shared Memory State Machine, a mechanism
 * for communicating single bit state information to remote processors.
 *
 * The implementation is based on two sections of shared memory; the first
 * holding the state bits and the second holding a matrix of subscription bits.
 *
 * The state bits are structured in entries of 32 bits, each belonging to one
 * system in the SoC. The entry belonging to the local system is considered
 * read-write, while the rest should be considered read-only.
 *
 * The subscription matrix consists of N bitmaps per entry, denoting interest
 * in updates of the entry for each of the N hosts. Upon updating a state bit
 * each host's subscription bitmap should be queried and the remote system
 * should be interrupted if they request so.
 *
 * The subscription matrix is laid out in entry-major order:
 * entry0: [host0 ... hostN]
 *      .
 *      .
 * entryM: [host0 ... hostN]
 *
 * A third, optional, shared memory region might contain information regarding
 * the number of entries in the state bitmap as well as number of columns in
 * the subscription matrix.
 */

/*
 * Shared memory identifiers, used to acquire handles to respective memory
 * region.
 */
#define SMEM_SMSM_SHARED_STATE          85
#define SMEM_SMSM_CPU_INTR_MASK         333
#define SMEM_SMSM_SIZE_INFO             419

/*
 * Default sizes, in case SMEM_SMSM_SIZE_INFO is not found.
 */
#define SMSM_DEFAULT_NUM_ENTRIES        8
#define SMSM_DEFAULT_NUM_HOSTS          3

struct smsm_entry;
struct smsm_host;

/**
 * struct qcom_smsm - smsm driver context
 * @dev:        smsm device pointer
 * @local_host: column in the subscription matrix representing this system
 * @num_hosts:  number of columns in the subscription matrix
 * @num_entries: number of entries in the state map and rows in the subscription
 *              matrix
 * @local_state: pointer to the local processor's state bits
 * @subscription: pointer to local processor's row in subscription matrix
 * @state:      smem state handle
 * @lock:       spinlock for read-modify-write of the outgoing state
 * @entries:    context for each of the entries
 * @hosts:      context for each of the hosts
 */
struct qcom_smsm {
        struct device *dev;

        u32 local_host;

        u32 num_hosts;
        u32 num_entries;

        u32 *local_state;
        u32 *subscription;
        struct qcom_smem_state *state;

        spinlock_t lock;

        struct smsm_entry *entries;
        struct smsm_host *hosts;
};

/**
 * struct smsm_entry - per remote processor entry context
 * @smsm:       back-reference to driver context
 * @domain:     IRQ domain for this entry, if representing a remote system
 * @irq_enabled: bitmap of which state bits IRQs are enabled
 * @irq_rising: bitmap tracking if rising bits should be propagated
 * @irq_falling: bitmap tracking if falling bits should be propagated
 * @last_value: snapshot of state bits last time the interrupts where propagated
 * @remote_state: pointer to this entry's state bits
 * @subscription: pointer to a row in the subscription matrix representing this
 *              entry
 */
struct smsm_entry {
        struct qcom_smsm *smsm;

        struct irq_domain *domain;
        DECLARE_BITMAP(irq_enabled, 32);
        DECLARE_BITMAP(irq_rising, 32);
        DECLARE_BITMAP(irq_falling, 32);
        u32 last_value;

        u32 *remote_state;
        u32 *subscription;
};

/**
 * struct smsm_host - representation of a remote host
 * @ipc_regmap: regmap for outgoing interrupt
 * @ipc_offset: offset in @ipc_regmap for outgoing interrupt
 * @ipc_bit:    bit in @ipc_regmap + @ipc_offset for outgoing interrupt
 */
struct smsm_host {
        struct regmap *ipc_regmap;
        int ipc_offset;
        int ipc_bit;
};

/**
 * smsm_update_bits() - change bit in outgoing entry and inform subscribers
 * @data:       smsm context pointer
 * @offset:     bit in the entry
 * @value:      new value
 *
 * Used to set and clear the bits in the outgoing/local entry and inform
 * subscribers about the change.
 */
static int smsm_update_bits(void *data, u32 mask, u32 value)
{
        struct qcom_smsm *smsm = data;
        struct smsm_host *hostp;
        unsigned long flags;
        u32 changes;
        u32 host;
        u32 orig;
        u32 val;

        spin_lock_irqsave(&smsm->lock, flags);

        /* Update the entry */
        val = orig = readl(smsm->local_state);
        val &= ~mask;
        val |= value;

        /* Don't signal if we didn't change the value */
        changes = val ^ orig;
        if (!changes) {
                spin_unlock_irqrestore(&smsm->lock, flags);
                goto done;
        }

        /* Write out the new value */
        writel(val, smsm->local_state);
        spin_unlock_irqrestore(&smsm->lock, flags);

        /* Make sure the value update is ordered before any kicks */
        wmb();

        /* Iterate over all hosts to check whom wants a kick */
        for (host = 0; host < smsm->num_hosts; host++) {
                hostp = &smsm->hosts[host];

                val = readl(smsm->subscription + host);
                if (val & changes && hostp->ipc_regmap) {
                        regmap_write(hostp->ipc_regmap,
                                     hostp->ipc_offset,
                                     BIT(hostp->ipc_bit));
                }
        }

done:
        return 0;
}

static const struct qcom_smem_state_ops smsm_state_ops = {
        .update_bits = smsm_update_bits,
};

/**
 * smsm_intr() - cascading IRQ handler for SMSM
 * @irq:        unused
 * @data:       entry related to this IRQ
 *
 * This function cascades an incoming interrupt from a remote system, based on
 * the state bits and configuration.
 */
static irqreturn_t smsm_intr(int irq, void *data)
{
        struct smsm_entry *entry = data;
        unsigned i;
        int irq_pin;
        u32 changed;
        u32 val;

        val = readl(entry->remote_state);
        changed = val ^ entry->last_value;
        entry->last_value = val;

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

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

        return IRQ_HANDLED;
}

/**
 * smsm_mask_irq() - un-subscribe from cascades of IRQs of a certain staus bit
 * @irqd:       IRQ handle to be masked
 *
 * This un-subscribes the local CPU from interrupts upon changes to the defines
 * status bit. The bit is also cleared from cascading.
 */
static void smsm_mask_irq(struct irq_data *irqd)
{
        struct smsm_entry *entry = irq_data_get_irq_chip_data(irqd);
        irq_hw_number_t irq = irqd_to_hwirq(irqd);
        struct qcom_smsm *smsm = entry->smsm;
        u32 val;

        if (entry->subscription) {
                val = readl(entry->subscription + smsm->local_host);
                val &= ~BIT(irq);
                writel(val, entry->subscription + smsm->local_host);
        }

        clear_bit(irq, entry->irq_enabled);
}

/**
 * smsm_unmask_irq() - subscribe to cascades of IRQs of a certain status bit
 * @irqd:       IRQ handle to be unmasked
 *

 * This subscribes the local CPU to interrupts upon changes to the defined
 * status bit. The bit is also marked for cascading.

 */
static void smsm_unmask_irq(struct irq_data *irqd)
{
        struct smsm_entry *entry = irq_data_get_irq_chip_data(irqd);
        irq_hw_number_t irq = irqd_to_hwirq(irqd);
        struct qcom_smsm *smsm = entry->smsm;
        u32 val;

        set_bit(irq, entry->irq_enabled);

        if (entry->subscription) {
                val = readl(entry->subscription + smsm->local_host);
                val |= BIT(irq);
                writel(val, entry->subscription + smsm->local_host);
        }
}

/**
 * smsm_set_irq_type() - updates the requested IRQ type for the cascading
 * @irqd:       consumer interrupt handle
 * @type:       requested flags
 */
static int smsm_set_irq_type(struct irq_data *irqd, unsigned int type)
{
        struct smsm_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 smsm_irq_chip = {
        .name           = "smsm",
        .irq_mask       = smsm_mask_irq,
        .irq_unmask     = smsm_unmask_irq,
        .irq_set_type   = smsm_set_irq_type,
};

/**
 * smsm_irq_map() - sets up a mapping for a cascaded IRQ
 * @d:          IRQ domain representing an entry
 * @irq:        IRQ to set up
 * @hw:         unused
 */
static int smsm_irq_map(struct irq_domain *d,
                        unsigned int irq,
                        irq_hw_number_t hw)
{
        struct smsm_entry *entry = d->host_data;

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

        return 0;
}

static const struct irq_domain_ops smsm_irq_ops = {
        .map = smsm_irq_map,
        .xlate = irq_domain_xlate_twocell,
};

/**
 * smsm_parse_ipc() - parses a qcom,ipc-%d device tree property
 * @smsm:       smsm driver context
 * @host_id:    index of the remote host to be resolved
 *
 * Parses device tree to acquire the information needed for sending the
 * outgoing interrupts to a remote host - identified by @host_id.
 */
static int smsm_parse_ipc(struct qcom_smsm *smsm, unsigned host_id)
{
        struct device_node *syscon;
        struct device_node *node = smsm->dev->of_node;
        struct smsm_host *host = &smsm->hosts[host_id];
        char key[16];
        int ret;

        snprintf(key, sizeof(key), "qcom,ipc-%d", host_id);
        syscon = of_parse_phandle(node, key, 0);
        if (!syscon)
                return 0;

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

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

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

        return 0;
}

/**
 * smsm_inbound_entry() - parse DT and set up an entry representing a remote system
 * @smsm:       smsm driver context
 * @entry:      entry context to be set up
 * @node:       dt node containing the entry's properties
 */
static int smsm_inbound_entry(struct qcom_smsm *smsm,
                              struct smsm_entry *entry,
                              struct device_node *node)
{
        int ret;
        int irq;

        irq = irq_of_parse_and_map(node, 0);
        if (!irq) {
                dev_err(smsm->dev, "failed to parse smsm interrupt\n");
                return -EINVAL;
        }

        ret = devm_request_threaded_irq(smsm->dev, irq,
                                        NULL, smsm_intr,
                                        IRQF_ONESHOT,
                                        "smsm", (void *)entry);
        if (ret) {
                dev_err(smsm->dev, "failed to request interrupt\n");
                return ret;
        }

        entry->domain = irq_domain_add_linear(node, 32, &smsm_irq_ops, entry);
        if (!entry->domain) {
                dev_err(smsm->dev, "failed to add irq_domain\n");
                return -ENOMEM;
        }

        return 0;
}

/**
 * smsm_get_size_info() - parse the optional memory segment for sizes
 * @smsm:       smsm driver context
 *
 * Attempt to acquire the number of hosts and entries from the optional shared
 * memory location. Not being able to find this segment should indicate that
 * we're on a older system where these values was hard coded to
 * SMSM_DEFAULT_NUM_ENTRIES and SMSM_DEFAULT_NUM_HOSTS.
 *
 * Returns 0 on success, negative errno on failure.
 */
static int smsm_get_size_info(struct qcom_smsm *smsm)
{
        size_t size;
        struct {
                u32 num_hosts;
                u32 num_entries;
                u32 reserved0;
                u32 reserved1;
        } *info;

        info = qcom_smem_get(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SIZE_INFO, &size);
        if (IS_ERR(info) && PTR_ERR(info) != -ENOENT) {
                if (PTR_ERR(info) != -EPROBE_DEFER)
                        dev_err(smsm->dev, "unable to retrieve smsm size info\n");
                return PTR_ERR(info);
        } else if (IS_ERR(info) || size != sizeof(*info)) {
                dev_warn(smsm->dev, "no smsm size info, using defaults\n");
                smsm->num_entries = SMSM_DEFAULT_NUM_ENTRIES;
                smsm->num_hosts = SMSM_DEFAULT_NUM_HOSTS;
                return 0;
        }

        smsm->num_entries = info->num_entries;
        smsm->num_hosts = info->num_hosts;

        dev_dbg(smsm->dev,
                "found custom size of smsm: %d entries %d hosts\n",
                smsm->num_entries, smsm->num_hosts);

        return 0;
}

static int qcom_smsm_probe(struct platform_device *pdev)
{
        struct device_node *local_node;
        struct device_node *node;
        struct smsm_entry *entry;
        struct qcom_smsm *smsm;
        u32 *intr_mask;
        size_t size;
        u32 *states;
        u32 id;
        int ret;

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

        ret = smsm_get_size_info(smsm);
        if (ret)
                return ret;

        smsm->entries = devm_kcalloc(&pdev->dev,
                                     smsm->num_entries,
                                     sizeof(struct smsm_entry),
                                     GFP_KERNEL);
        if (!smsm->entries)
                return -ENOMEM;

        smsm->hosts = devm_kcalloc(&pdev->dev,
                                   smsm->num_hosts,
                                   sizeof(struct smsm_host),
                                   GFP_KERNEL);
        if (!smsm->hosts)
                return -ENOMEM;

        for_each_child_of_node(pdev->dev.of_node, local_node) {
                if (of_find_property(local_node, "#qcom,smem-state-cells", NULL))
                        break;
        }
        if (!local_node) {
                dev_err(&pdev->dev, "no state entry\n");
                return -EINVAL;
        }

        of_property_read_u32(pdev->dev.of_node,
                             "qcom,local-host",
                             &smsm->local_host);

        /* Parse the host properties */
        for (id = 0; id < smsm->num_hosts; id++) {
                ret = smsm_parse_ipc(smsm, id);
                if (ret < 0)
                        return ret;
        }

        /* Acquire the main SMSM state vector */
        ret = qcom_smem_alloc(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SHARED_STATE,
                              smsm->num_entries * sizeof(u32));
        if (ret < 0 && ret != -EEXIST) {
                dev_err(&pdev->dev, "unable to allocate shared state entry\n");
                return ret;
        }

        states = qcom_smem_get(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SHARED_STATE, NULL);
        if (IS_ERR(states)) {
                dev_err(&pdev->dev, "Unable to acquire shared state entry\n");
                return PTR_ERR(states);
        }

        /* Acquire the list of interrupt mask vectors */
        size = smsm->num_entries * smsm->num_hosts * sizeof(u32);
        ret = qcom_smem_alloc(QCOM_SMEM_HOST_ANY, SMEM_SMSM_CPU_INTR_MASK, size);
        if (ret < 0 && ret != -EEXIST) {
                dev_err(&pdev->dev, "unable to allocate smsm interrupt mask\n");
                return ret;
        }

        intr_mask = qcom_smem_get(QCOM_SMEM_HOST_ANY, SMEM_SMSM_CPU_INTR_MASK, NULL);
        if (IS_ERR(intr_mask)) {
                dev_err(&pdev->dev, "unable to acquire shared memory interrupt mask\n");
                return PTR_ERR(intr_mask);
        }

        /* Setup the reference to the local state bits */
        smsm->local_state = states + smsm->local_host;
        smsm->subscription = intr_mask + smsm->local_host * smsm->num_hosts;

        /* Register the outgoing state */
        smsm->state = qcom_smem_state_register(local_node, &smsm_state_ops, smsm);
        if (IS_ERR(smsm->state)) {
                dev_err(smsm->dev, "failed to register qcom_smem_state\n");
                return PTR_ERR(smsm->state);
        }

        /* Register handlers for remote processor entries of interest. */
        for_each_available_child_of_node(pdev->dev.of_node, node) {
                if (!of_property_read_bool(node, "interrupt-controller"))
                        continue;

                ret = of_property_read_u32(node, "reg", &id);
                if (ret || id >= smsm->num_entries) {
                        dev_err(&pdev->dev, "invalid reg of entry\n");
                        if (!ret)
                                ret = -EINVAL;
                        goto unwind_interfaces;
                }
                entry = &smsm->entries[id];

                entry->smsm = smsm;
                entry->remote_state = states + id;

                /* Setup subscription pointers and unsubscribe to any kicks */
                entry->subscription = intr_mask + id * smsm->num_hosts;
                writel(0, entry->subscription + smsm->local_host);

                ret = smsm_inbound_entry(smsm, entry, node);
                if (ret < 0)
                        goto unwind_interfaces;
        }

        platform_set_drvdata(pdev, smsm);

        return 0;

unwind_interfaces:
        for (id = 0; id < smsm->num_entries; id++)
                if (smsm->entries[id].domain)
                        irq_domain_remove(smsm->entries[id].domain);

        qcom_smem_state_unregister(smsm->state);

        return ret;
}

static int qcom_smsm_remove(struct platform_device *pdev)
{
        struct qcom_smsm *smsm = platform_get_drvdata(pdev);
        unsigned id;

        for (id = 0; id < smsm->num_entries; id++)
                if (smsm->entries[id].domain)
                        irq_domain_remove(smsm->entries[id].domain);

        qcom_smem_state_unregister(smsm->state);

        return 0;
}

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

static struct platform_driver qcom_smsm_driver = {
        .probe = qcom_smsm_probe,
        .remove = qcom_smsm_remove,
        .driver  = {
                .name  = "qcom-smsm",
                .of_match_table = qcom_smsm_of_match,
        },
};
module_platform_driver(qcom_smsm_driver);

MODULE_DESCRIPTION("Qualcomm Shared Memory State Machine driver");
MODULE_LICENSE("GPL v2");