// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * i2c-smbus.c - SMBus extensions to the I2C protocol
 *
 * Copyright (C) 2008 David Brownell
 * Copyright (C) 2010-2019 Jean Delvare <jdelvare@suse.de>
 */

#include <linux/device.h>
#include <linux/dmi.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/workqueue.h>

struct i2c_smbus_alert {
        struct work_struct      alert;
        struct i2c_client       *ara;           /* Alert response address */
};

struct alert_data {
        unsigned short          addr;
        enum i2c_alert_protocol type;
        unsigned int            data;
};

/* If this is the alerting device, notify its driver */
static int smbus_do_alert(struct device *dev, void *addrp)
{
        struct i2c_client *client = i2c_verify_client(dev);
        struct alert_data *data = addrp;
        struct i2c_driver *driver;
        int ret;

        if (!client || client->addr != data->addr)
                return 0;
        if (client->flags & I2C_CLIENT_TEN)
                return 0;

        /*
         * Drivers should either disable alerts, or provide at least
         * a minimal handler.  Lock so the driver won't change.
         */
        device_lock(dev);
        if (client->dev.driver) {
                driver = to_i2c_driver(client->dev.driver);
                if (driver->alert) {
                        /* Stop iterating after we find the device */
                        driver->alert(client, data->type, data->data);
                        ret = -EBUSY;
                } else {
                        dev_warn(&client->dev, "no driver alert()!\n");
                        ret = -EOPNOTSUPP;
                }
        } else {
                dev_dbg(&client->dev, "alert with no driver\n");
                ret = -ENODEV;
        }
        device_unlock(dev);

        return ret;
}

/* Same as above, but call back all drivers with alert handler */

static int smbus_do_alert_force(struct device *dev, void *addrp)
{
        struct i2c_client *client = i2c_verify_client(dev);
        struct alert_data *data = addrp;
        struct i2c_driver *driver;

        if (!client || (client->flags & I2C_CLIENT_TEN))
                return 0;

        /*
         * Drivers should either disable alerts, or provide at least
         * a minimal handler. Lock so the driver won't change.
         */
        device_lock(dev);
        if (client->dev.driver) {
                driver = to_i2c_driver(client->dev.driver);
                if (driver->alert)
                        driver->alert(client, data->type, data->data);
        }
        device_unlock(dev);

        return 0;
}

/*
 * The alert IRQ handler needs to hand work off to a task which can issue
 * SMBus calls, because those sleeping calls can't be made in IRQ context.
 */
static irqreturn_t smbus_alert(int irq, void *d)
{
        struct i2c_smbus_alert *alert = d;
        struct i2c_client *ara;
        unsigned short prev_addr = I2C_CLIENT_END; /* Not a valid address */

        ara = alert->ara;

        for (;;) {
                s32 status;
                struct alert_data data;

                /*
                 * Devices with pending alerts reply in address order, low
                 * to high, because of slave transmit arbitration.  After
                 * responding, an SMBus device stops asserting SMBALERT#.
                 *
                 * Note that SMBus 2.0 reserves 10-bit addresses for future
                 * use.  We neither handle them, nor try to use PEC here.
                 */
                status = i2c_smbus_read_byte(ara);
                if (status < 0)
                        break;

                data.data = status & 1;
                data.addr = status >> 1;
                data.type = I2C_PROTOCOL_SMBUS_ALERT;

                dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
                        data.addr, data.data);

                /* Notify driver for the device which issued the alert */
                status = device_for_each_child(&ara->adapter->dev, &data,
                                               smbus_do_alert);
                /*
                 * If we read the same address more than once, and the alert
                 * was not handled by a driver, it won't do any good to repeat
                 * the loop because it will never terminate. Try again, this
                 * time calling the alert handlers of all devices connected to
                 * the bus, and abort the loop afterwards. If this helps, we
                 * are all set. If it doesn't, there is nothing else we can do,
                 * so we might as well abort the loop.
                 * Note: This assumes that a driver with alert handler handles
                 * the alert properly and clears it if necessary.
                 */
                if (data.addr == prev_addr && status != -EBUSY) {
                        device_for_each_child(&ara->adapter->dev, &data,
                                              smbus_do_alert_force);
                        break;
                }
                prev_addr = data.addr;
        }

        return IRQ_HANDLED;
}

static void smbalert_work(struct work_struct *work)
{
        struct i2c_smbus_alert *alert;

        alert = container_of(work, struct i2c_smbus_alert, alert);

        smbus_alert(0, alert);

}

/* Setup SMBALERT# infrastructure */
static int smbalert_probe(struct i2c_client *ara)
{
        struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
        struct i2c_smbus_alert *alert;
        struct i2c_adapter *adapter = ara->adapter;
        unsigned long irqflags = IRQF_SHARED | IRQF_ONESHOT;
        struct gpio_desc *gpiod;
        int res, irq;

        alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
                             GFP_KERNEL);
        if (!alert)
                return -ENOMEM;

        if (setup) {
                irq = setup->irq;
        } else {
                irq = fwnode_irq_get_byname(dev_fwnode(adapter->dev.parent),
                                            "smbus_alert");
                if (irq <= 0) {
                        gpiod = devm_gpiod_get(adapter->dev.parent, "smbalert", GPIOD_IN);
                        if (IS_ERR(gpiod))
                                return PTR_ERR(gpiod);

                        irq = gpiod_to_irq(gpiod);
                        if (irq <= 0)
                                return irq;

                        irqflags |= IRQF_TRIGGER_FALLING;
                }
        }

        INIT_WORK(&alert->alert, smbalert_work);
        alert->ara = ara;

        if (irq > 0) {
                res = devm_request_threaded_irq(&ara->dev, irq, NULL, smbus_alert,
                                                irqflags, "smbus_alert", alert);
                if (res)
                        return res;
        }

        i2c_set_clientdata(ara, alert);
        dev_info(&adapter->dev, "supports SMBALERT#\n");

        return 0;
}

/* IRQ and memory resources are managed so they are freed automatically */
static void smbalert_remove(struct i2c_client *ara)
{
        struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);

        cancel_work_sync(&alert->alert);
}

static const struct i2c_device_id smbalert_ids[] = {
        { .name = "smbus_alert" },
        { /* LIST END */ }
};
MODULE_DEVICE_TABLE(i2c, smbalert_ids);

static struct i2c_driver smbalert_driver = {
        .driver = {
                .name   = "smbus_alert",
        },
        .probe          = smbalert_probe,
        .remove         = smbalert_remove,
        .id_table       = smbalert_ids,
};

/**
 * i2c_handle_smbus_alert - Handle an SMBus alert
 * @ara: the ARA client on the relevant adapter
 * Context: can't sleep
 *
 * Helper function to be called from an I2C bus driver's interrupt
 * handler. It will schedule the alert work, in turn calling the
 * corresponding I2C device driver's alert function.
 *
 * It is assumed that ara is a valid i2c client previously returned by
 * i2c_new_smbus_alert_device().
 */
int i2c_handle_smbus_alert(struct i2c_client *ara)
{
        struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);

        return schedule_work(&alert->alert);
}
EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);

module_i2c_driver(smbalert_driver);

#if IS_ENABLED(CONFIG_I2C_SLAVE)
#define SMBUS_HOST_NOTIFY_LEN   3
struct i2c_slave_host_notify_status {
        u8 index;
        u8 addr;
};

static int i2c_slave_host_notify_cb(struct i2c_client *client,
                                    enum i2c_slave_event event, u8 *val)
{
        struct i2c_slave_host_notify_status *status = client->dev.platform_data;

        switch (event) {
        case I2C_SLAVE_WRITE_RECEIVED:
                /* We only retrieve the first byte received (addr)
                 * since there is currently no support to retrieve the data
                 * parameter from the client.
                 */
                if (status->index == 0)
                        status->addr = *val;
                if (status->index < U8_MAX)
                        status->index++;
                break;
        case I2C_SLAVE_STOP:
                if (status->index == SMBUS_HOST_NOTIFY_LEN)
                        i2c_handle_smbus_host_notify(client->adapter,
                                                     status->addr);
                fallthrough;
        case I2C_SLAVE_WRITE_REQUESTED:
                status->index = 0;
                break;
        case I2C_SLAVE_READ_REQUESTED:
        case I2C_SLAVE_READ_PROCESSED:
                *val = 0xff;
                break;
        }

        return 0;
}

/**
 * i2c_new_slave_host_notify_device - get a client for SMBus host-notify support
 * @adapter: the target adapter
 * Context: can sleep
 *
 * Setup handling of the SMBus host-notify protocol on a given I2C bus segment.
 *
 * Handling is done by creating a device and its callback and handling data
 * received via the SMBus host-notify address (0x8)
 *
 * This returns the client, which should be ultimately freed using
 * i2c_free_slave_host_notify_device(); or an ERRPTR to indicate an error.
 */
struct i2c_client *i2c_new_slave_host_notify_device(struct i2c_adapter *adapter)
{
        struct i2c_board_info host_notify_board_info = {
                I2C_BOARD_INFO("smbus_host_notify", 0x08),
                .flags  = I2C_CLIENT_SLAVE,
        };
        struct i2c_slave_host_notify_status *status;
        struct i2c_client *client;
        int ret;

        status = kzalloc_obj(struct i2c_slave_host_notify_status);
        if (!status)
                return ERR_PTR(-ENOMEM);

        host_notify_board_info.platform_data = status;

        client = i2c_new_client_device(adapter, &host_notify_board_info);
        if (IS_ERR(client)) {
                kfree(status);
                return client;
        }

        ret = i2c_slave_register(client, i2c_slave_host_notify_cb);
        if (ret) {
                i2c_unregister_device(client);
                kfree(status);
                return ERR_PTR(ret);
        }

        return client;
}
EXPORT_SYMBOL_GPL(i2c_new_slave_host_notify_device);

/**
 * i2c_free_slave_host_notify_device - free the client for SMBus host-notify
 * support
 * @client: the client to free
 * Context: can sleep
 *
 * Free the i2c_client allocated via i2c_new_slave_host_notify_device
 */
void i2c_free_slave_host_notify_device(struct i2c_client *client)
{
        if (IS_ERR_OR_NULL(client))
                return;

        i2c_slave_unregister(client);
        kfree(client->dev.platform_data);
        i2c_unregister_device(client);
}
EXPORT_SYMBOL_GPL(i2c_free_slave_host_notify_device);
#endif

/*
 * SPD is not part of SMBus but we include it here for convenience as the
 * target systems are the same.
 * Restrictions to automatic SPD instantiation:
 *  - Only works if all filled slots have the same memory type
 *  - Only works for (LP)DDR memory types up to DDR5
 *  - Only works on systems with 1 to 8 memory slots
 */
#if IS_ENABLED(CONFIG_DMI)
static void i2c_register_spd(struct i2c_adapter *adap, bool write_disabled)
{
        int n, slot_count = 0, dimm_count = 0;
        u16 handle;
        u8 common_mem_type = 0x0, mem_type;
        u64 mem_size;
        bool instantiate = true;
        const char *name;

        while ((handle = dmi_memdev_handle(slot_count)) != 0xffff) {
                slot_count++;

                /* Skip empty slots */
                mem_size = dmi_memdev_size(handle);
                if (!mem_size)
                        continue;

                /* Skip undefined memory type */
                mem_type = dmi_memdev_type(handle);
                if (mem_type <= 0x02)           /* Invalid, Other, Unknown */
                        continue;

                if (!common_mem_type) {
                        /* First filled slot */
                        common_mem_type = mem_type;
                } else {
                        /* Check that all filled slots have the same type */
                        if (mem_type != common_mem_type) {
                                dev_warn(&adap->dev,
                                         "Different memory types mixed, not instantiating SPD\n");
                                return;
                        }
                }
                dimm_count++;
        }

        /* No useful DMI data, bail out */
        if (!dimm_count)
                return;

        /*
         * The max number of SPD EEPROMs that can be addressed per bus is 8.
         * If more slots are present either muxed or multiple busses are
         * necessary or the additional slots are ignored.
         */
        slot_count = min(slot_count, 8);

        /*
         * Memory types could be found at section 7.18.2 (Memory Device — Type), table 78
         * https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.6.0.pdf
         */
        switch (common_mem_type) {
        case 0x12:      /* DDR */
        case 0x13:      /* DDR2 */
        case 0x18:      /* DDR3 */
        case 0x1B:      /* LPDDR */
        case 0x1C:      /* LPDDR2 */
        case 0x1D:      /* LPDDR3 */
                name = "spd";
                break;
        case 0x1A:      /* DDR4 */
        case 0x1E:      /* LPDDR4 */
                name = "ee1004";
                break;
        case 0x22:      /* DDR5 */
        case 0x23:      /* LPDDR5 */
                name = "spd5118";
                instantiate = !write_disabled;
                break;
        default:
                dev_info(&adap->dev,
                         "Memory type 0x%02x not supported yet, not instantiating SPD\n",
                         common_mem_type);
                return;
        }

        /*
         * We don't know in which slots the memory modules are. We could
         * try to guess from the slot names, but that would be rather complex
         * and unreliable, so better probe all possible addresses until we
         * have found all memory modules.
         */
        for (n = 0; n < slot_count && dimm_count; n++) {
                struct i2c_board_info info;
                unsigned short addr_list[2];

                memset(&info, 0, sizeof(struct i2c_board_info));
                strscpy(info.type, name, I2C_NAME_SIZE);
                addr_list[0] = 0x50 + n;
                addr_list[1] = I2C_CLIENT_END;

                if (!instantiate)
                        continue;

                if (!IS_ERR(i2c_new_scanned_device(adap, &info, addr_list, NULL))) {
                        dev_info(&adap->dev,
                                 "Successfully instantiated SPD at 0x%hx\n",
                                 addr_list[0]);
                        dimm_count--;
                }
        }
}

void i2c_register_spd_write_disable(struct i2c_adapter *adap)
{
        i2c_register_spd(adap, true);
}
EXPORT_SYMBOL_GPL(i2c_register_spd_write_disable);

void i2c_register_spd_write_enable(struct i2c_adapter *adap)
{
        i2c_register_spd(adap, false);
}
EXPORT_SYMBOL_GPL(i2c_register_spd_write_enable);

#endif

MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
MODULE_DESCRIPTION("SMBus protocol extensions support");
MODULE_LICENSE("GPL");