// SPDX-License-Identifier: GPL-2.0

#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/fsi-sbefifo.h>
#include <linux/gfp.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/fsi-occ.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <asm/unaligned.h>

#define OCC_SRAM_BYTES          4096
#define OCC_CMD_DATA_BYTES      4090
#define OCC_RESP_DATA_BYTES     4089

#define OCC_SRAM_CMD_ADDR       0xFFFBE000
#define OCC_SRAM_RSP_ADDR       0xFFFBF000

/*
 * Assume we don't have much FFDC, if we do we'll overflow and
 * fail the command. This needs to be big enough for simple
 * commands as well.
 */
#define OCC_SBE_STATUS_WORDS    32

#define OCC_TIMEOUT_MS          1000
#define OCC_CMD_IN_PRG_WAIT_MS  50

struct occ {
        struct device *dev;
        struct device *sbefifo;
        char name[32];
        int idx;
        struct miscdevice mdev;
        struct mutex occ_lock;
};

#define to_occ(x)       container_of((x), struct occ, mdev)

struct occ_response {
        u8 seq_no;
        u8 cmd_type;
        u8 return_status;
        __be16 data_length;
        u8 data[OCC_RESP_DATA_BYTES + 2];       /* two bytes checksum */
} __packed;

struct occ_client {
        struct occ *occ;
        struct mutex lock;
        size_t data_size;
        size_t read_offset;
        u8 *buffer;
};

#define to_client(x)    container_of((x), struct occ_client, xfr)

static DEFINE_IDA(occ_ida);

static int occ_open(struct inode *inode, struct file *file)
{
        struct occ_client *client = kzalloc(sizeof(*client), GFP_KERNEL);
        struct miscdevice *mdev = file->private_data;
        struct occ *occ = to_occ(mdev);

        if (!client)
                return -ENOMEM;

        client->buffer = (u8 *)__get_free_page(GFP_KERNEL);
        if (!client->buffer) {
                kfree(client);
                return -ENOMEM;
        }

        client->occ = occ;
        mutex_init(&client->lock);
        file->private_data = client;

        /* We allocate a 1-page buffer, make sure it all fits */
        BUILD_BUG_ON((OCC_CMD_DATA_BYTES + 3) > PAGE_SIZE);
        BUILD_BUG_ON((OCC_RESP_DATA_BYTES + 7) > PAGE_SIZE);

        return 0;
}

static ssize_t occ_read(struct file *file, char __user *buf, size_t len,
                        loff_t *offset)
{
        struct occ_client *client = file->private_data;
        ssize_t rc = 0;

        if (!client)
                return -ENODEV;

        if (len > OCC_SRAM_BYTES)
                return -EINVAL;

        mutex_lock(&client->lock);

        /* This should not be possible ... */
        if (WARN_ON_ONCE(client->read_offset > client->data_size)) {
                rc = -EIO;
                goto done;
        }

        /* Grab how much data we have to read */
        rc = min(len, client->data_size - client->read_offset);
        if (copy_to_user(buf, client->buffer + client->read_offset, rc))
                rc = -EFAULT;
        else
                client->read_offset += rc;

 done:
        mutex_unlock(&client->lock);

        return rc;
}

static ssize_t occ_write(struct file *file, const char __user *buf,
                         size_t len, loff_t *offset)
{
        struct occ_client *client = file->private_data;
        size_t rlen, data_length;
        u16 checksum = 0;
        ssize_t rc, i;
        u8 *cmd;

        if (!client)
                return -ENODEV;

        if (len > (OCC_CMD_DATA_BYTES + 3) || len < 3)
                return -EINVAL;

        mutex_lock(&client->lock);

        /* Construct the command */
        cmd = client->buffer;

        /* Sequence number (we could increment and compare with response) */
        cmd[0] = 1;

        /*
         * Copy the user command (assume user data follows the occ command
         * format)
         * byte 0: command type
         * bytes 1-2: data length (msb first)
         * bytes 3-n: data
         */
        if (copy_from_user(&cmd[1], buf, len)) {
                rc = -EFAULT;
                goto done;
        }

        /* Extract data length */
        data_length = (cmd[2] << 8) + cmd[3];
        if (data_length > OCC_CMD_DATA_BYTES) {
                rc = -EINVAL;
                goto done;
        }

        /* Calculate checksum */
        for (i = 0; i < data_length + 4; ++i)
                checksum += cmd[i];

        cmd[data_length + 4] = checksum >> 8;
        cmd[data_length + 5] = checksum & 0xFF;

        /* Submit command */
        rlen = PAGE_SIZE;
        rc = fsi_occ_submit(client->occ->dev, cmd, data_length + 6, cmd,
                            &rlen);
        if (rc)
                goto done;

        /* Set read tracking data */
        client->data_size = rlen;
        client->read_offset = 0;

        /* Done */
        rc = len;

 done:
        mutex_unlock(&client->lock);

        return rc;
}

static int occ_release(struct inode *inode, struct file *file)
{
        struct occ_client *client = file->private_data;

        free_page((unsigned long)client->buffer);
        kfree(client);

        return 0;
}

static const struct file_operations occ_fops = {
        .owner = THIS_MODULE,
        .open = occ_open,
        .read = occ_read,
        .write = occ_write,
        .release = occ_release,
};

static int occ_verify_checksum(struct occ_response *resp, u16 data_length)
{
        /* Fetch the two bytes after the data for the checksum. */
        u16 checksum_resp = get_unaligned_be16(&resp->data[data_length]);
        u16 checksum;
        u16 i;

        checksum = resp->seq_no;
        checksum += resp->cmd_type;
        checksum += resp->return_status;
        checksum += (data_length >> 8) + (data_length & 0xFF);

        for (i = 0; i < data_length; ++i)
                checksum += resp->data[i];

        if (checksum != checksum_resp)
                return -EBADMSG;

        return 0;
}

static int occ_getsram(struct occ *occ, u32 address, void *data, ssize_t len)
{
        u32 data_len = ((len + 7) / 8) * 8;     /* must be multiples of 8 B */
        size_t resp_len, resp_data_len;
        __be32 *resp, cmd[5];
        int rc;

        /*
         * Magic sequence to do SBE getsram command. SBE will fetch data from
         * specified SRAM address.
         */
        cmd[0] = cpu_to_be32(0x5);
        cmd[1] = cpu_to_be32(SBEFIFO_CMD_GET_OCC_SRAM);
        cmd[2] = cpu_to_be32(1);
        cmd[3] = cpu_to_be32(address);
        cmd[4] = cpu_to_be32(data_len);

        resp_len = (data_len >> 2) + OCC_SBE_STATUS_WORDS;
        resp = kzalloc(resp_len << 2, GFP_KERNEL);
        if (!resp)
                return -ENOMEM;

        rc = sbefifo_submit(occ->sbefifo, cmd, 5, resp, &resp_len);
        if (rc)
                goto free;

        rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_GET_OCC_SRAM,
                                  resp, resp_len, &resp_len);
        if (rc)
                goto free;

        resp_data_len = be32_to_cpu(resp[resp_len - 1]);
        if (resp_data_len != data_len) {
                dev_err(occ->dev, "SRAM read expected %d bytes got %zd\n",
                        data_len, resp_data_len);
                rc = -EBADMSG;
        } else {
                memcpy(data, resp, len);
        }

free:
        /* Convert positive SBEI status */
        if (rc > 0) {
                dev_err(occ->dev, "SRAM read returned failure status: %08x\n",
                        rc);
                rc = -EBADMSG;
        }

        kfree(resp);
        return rc;
}

static int occ_putsram(struct occ *occ, u32 address, const void *data,
                       ssize_t len)
{
        size_t cmd_len, buf_len, resp_len, resp_data_len;
        u32 data_len = ((len + 7) / 8) * 8;     /* must be multiples of 8 B */
        __be32 *buf;
        int rc;

        /*
         * We use the same buffer for command and response, make
         * sure it's big enough
         */
        resp_len = OCC_SBE_STATUS_WORDS;
        cmd_len = (data_len >> 2) + 5;
        buf_len = max(cmd_len, resp_len);
        buf = kzalloc(buf_len << 2, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        /*
         * Magic sequence to do SBE putsram command. SBE will transfer
         * data to specified SRAM address.
         */
        buf[0] = cpu_to_be32(cmd_len);
        buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
        buf[2] = cpu_to_be32(1);
        buf[3] = cpu_to_be32(address);
        buf[4] = cpu_to_be32(data_len);

        memcpy(&buf[5], data, len);

        rc = sbefifo_submit(occ->sbefifo, buf, cmd_len, buf, &resp_len);
        if (rc)
                goto free;

        rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
                                  buf, resp_len, &resp_len);
        if (rc)
                goto free;

        if (resp_len != 1) {
                dev_err(occ->dev, "SRAM write response length invalid: %zd\n",
                        resp_len);
                rc = -EBADMSG;
        } else {
                resp_data_len = be32_to_cpu(buf[0]);
                if (resp_data_len != data_len) {
                        dev_err(occ->dev,
                                "SRAM write expected %d bytes got %zd\n",
                                data_len, resp_data_len);
                        rc = -EBADMSG;
                }
        }

free:
        /* Convert positive SBEI status */
        if (rc > 0) {
                dev_err(occ->dev, "SRAM write returned failure status: %08x\n",
                        rc);
                rc = -EBADMSG;
        }

        kfree(buf);
        return rc;
}

static int occ_trigger_attn(struct occ *occ)
{
        __be32 buf[OCC_SBE_STATUS_WORDS];
        size_t resp_len, resp_data_len;
        int rc;

        BUILD_BUG_ON(OCC_SBE_STATUS_WORDS < 7);
        resp_len = OCC_SBE_STATUS_WORDS;

        buf[0] = cpu_to_be32(0x5 + 0x2);        /* Chip-op length in words */
        buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
        buf[2] = cpu_to_be32(0x3);              /* Mode: Circular */
        buf[3] = cpu_to_be32(0x0);              /* Address: ignore in mode 3 */
        buf[4] = cpu_to_be32(0x8);              /* Data length in bytes */
        buf[5] = cpu_to_be32(0x20010000);       /* Trigger OCC attention */
        buf[6] = 0;

        rc = sbefifo_submit(occ->sbefifo, buf, 7, buf, &resp_len);
        if (rc)
                goto error;

        rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
                                  buf, resp_len, &resp_len);
        if (rc)
                goto error;

        if (resp_len != 1) {
                dev_err(occ->dev, "SRAM attn response length invalid: %zd\n",
                        resp_len);
                rc = -EBADMSG;
        } else {
                resp_data_len = be32_to_cpu(buf[0]);
                if (resp_data_len != 8) {
                        dev_err(occ->dev,
                                "SRAM attn expected 8 bytes got %zd\n",
                                resp_data_len);
                        rc = -EBADMSG;
                }
        }

 error:
        /* Convert positive SBEI status */
        if (rc > 0) {
                dev_err(occ->dev, "SRAM attn returned failure status: %08x\n",
                        rc);
                rc = -EBADMSG;
        }

        return rc;
}

int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
                   void *response, size_t *resp_len)
{
        const unsigned long timeout = msecs_to_jiffies(OCC_TIMEOUT_MS);
        const unsigned long wait_time =
                msecs_to_jiffies(OCC_CMD_IN_PRG_WAIT_MS);
        struct occ *occ = dev_get_drvdata(dev);
        struct occ_response *resp = response;
        u8 seq_no;
        u16 resp_data_length;
        unsigned long start;
        int rc;

        if (!occ)
                return -ENODEV;

        if (*resp_len < 7) {
                dev_dbg(dev, "Bad resplen %zd\n", *resp_len);
                return -EINVAL;
        }

        mutex_lock(&occ->occ_lock);

        /* Extract the seq_no from the command (first byte) */
        seq_no = *(const u8 *)request;
        rc = occ_putsram(occ, OCC_SRAM_CMD_ADDR, request, req_len);
        if (rc)
                goto done;

        rc = occ_trigger_attn(occ);
        if (rc)
                goto done;

        /* Read occ response header */
        start = jiffies;
        do {
                rc = occ_getsram(occ, OCC_SRAM_RSP_ADDR, resp, 8);
                if (rc)
                        goto done;

                if (resp->return_status == OCC_RESP_CMD_IN_PRG ||
                    resp->seq_no != seq_no) {
                        rc = -ETIMEDOUT;

                        if (time_after(jiffies, start + timeout)) {
                                dev_err(occ->dev, "resp timeout status=%02x "
                                        "resp seq_no=%d our seq_no=%d\n",
                                        resp->return_status, resp->seq_no,
                                        seq_no);
                                goto done;
                        }

                        set_current_state(TASK_UNINTERRUPTIBLE);
                        schedule_timeout(wait_time);
                }
        } while (rc);

        /* Extract size of response data */
        resp_data_length = get_unaligned_be16(&resp->data_length);

        /* Message size is data length + 5 bytes header + 2 bytes checksum */
        if ((resp_data_length + 7) > *resp_len) {
                rc = -EMSGSIZE;
                goto done;
        }

        dev_dbg(dev, "resp_status=%02x resp_data_len=%d\n",
                resp->return_status, resp_data_length);

        /* Grab the rest */
        if (resp_data_length > 1) {
                /* already got 3 bytes resp, also need 2 bytes checksum */
                rc = occ_getsram(occ, OCC_SRAM_RSP_ADDR + 8,
                                 &resp->data[3], resp_data_length - 1);
                if (rc)
                        goto done;
        }

        *resp_len = resp_data_length + 7;
        rc = occ_verify_checksum(resp, resp_data_length);

 done:
        mutex_unlock(&occ->occ_lock);

        return rc;
}
EXPORT_SYMBOL_GPL(fsi_occ_submit);

static int occ_unregister_child(struct device *dev, void *data)
{
        struct platform_device *hwmon_dev = to_platform_device(dev);

        platform_device_unregister(hwmon_dev);

        return 0;
}

static int occ_probe(struct platform_device *pdev)
{
        int rc;
        u32 reg;
        struct occ *occ;
        struct platform_device *hwmon_dev;
        struct device *dev = &pdev->dev;
        struct platform_device_info hwmon_dev_info = {
                .parent = dev,
                .name = "occ-hwmon",
        };

        occ = devm_kzalloc(dev, sizeof(*occ), GFP_KERNEL);
        if (!occ)
                return -ENOMEM;

        occ->dev = dev;
        occ->sbefifo = dev->parent;
        mutex_init(&occ->occ_lock);

        if (dev->of_node) {
                rc = of_property_read_u32(dev->of_node, "reg", &reg);
                if (!rc) {
                        /* make sure we don't have a duplicate from dts */
                        occ->idx = ida_simple_get(&occ_ida, reg, reg + 1,
                                                  GFP_KERNEL);
                        if (occ->idx < 0)
                                occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX,
                                                          GFP_KERNEL);
                } else {
                        occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX,
                                                  GFP_KERNEL);
                }
        } else {
                occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX, GFP_KERNEL);
        }

        platform_set_drvdata(pdev, occ);

        snprintf(occ->name, sizeof(occ->name), "occ%d", occ->idx);
        occ->mdev.fops = &occ_fops;
        occ->mdev.minor = MISC_DYNAMIC_MINOR;
        occ->mdev.name = occ->name;
        occ->mdev.parent = dev;

        rc = misc_register(&occ->mdev);
        if (rc) {
                dev_err(dev, "failed to register miscdevice: %d\n", rc);
                ida_simple_remove(&occ_ida, occ->idx);
                return rc;
        }

        hwmon_dev_info.id = occ->idx;
        hwmon_dev = platform_device_register_full(&hwmon_dev_info);
        if (!hwmon_dev)
                dev_warn(dev, "failed to create hwmon device\n");

        return 0;
}

static int occ_remove(struct platform_device *pdev)
{
        struct occ *occ = platform_get_drvdata(pdev);

        misc_deregister(&occ->mdev);

        device_for_each_child(&pdev->dev, NULL, occ_unregister_child);

        ida_simple_remove(&occ_ida, occ->idx);

        return 0;
}

static const struct of_device_id occ_match[] = {
        { .compatible = "ibm,p9-occ" },
        { },
};

static struct platform_driver occ_driver = {
        .driver = {
                .name = "occ",
                .of_match_table = occ_match,
        },
        .probe  = occ_probe,
        .remove = occ_remove,
};

static int occ_init(void)
{
        return platform_driver_register(&occ_driver);
}

static void occ_exit(void)
{
        platform_driver_unregister(&occ_driver);

        ida_destroy(&occ_ida);
}

module_init(occ_init);
module_exit(occ_exit);

MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
MODULE_DESCRIPTION("BMC P9 OCC driver");
MODULE_LICENSE("GPL");