// SPDX-License-Identifier: GPL-2.0-only
/*
 * OPAL Operator Panel Display Driver
 *
 * Copyright 2016, Suraj Jitindar Singh, IBM Corporation.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>

#include <asm/opal.h>

/*
 * This driver creates a character device (/dev/op_panel) which exposes the
 * operator panel (character LCD display) on IBM Power Systems machines
 * with FSPs.
 * A character buffer written to the device will be displayed on the
 * operator panel.
 */

static DEFINE_MUTEX(oppanel_mutex);

static u32              num_lines, oppanel_size;
static oppanel_line_t   *oppanel_lines;
static char             *oppanel_data;

static loff_t oppanel_llseek(struct file *filp, loff_t offset, int whence)
{
        return fixed_size_llseek(filp, offset, whence, oppanel_size);
}

static ssize_t oppanel_read(struct file *filp, char __user *userbuf, size_t len,
                            loff_t *f_pos)
{
        return simple_read_from_buffer(userbuf, len, f_pos, oppanel_data,
                        oppanel_size);
}

static int __op_panel_update_display(void)
{
        struct opal_msg msg;
        int rc, token;

        token = opal_async_get_token_interruptible();
        if (token < 0) {
                if (token != -ERESTARTSYS)
                        pr_debug("Couldn't get OPAL async token [token=%d]\n",
                                token);
                return token;
        }

        rc = opal_write_oppanel_async(token, oppanel_lines, num_lines);
        switch (rc) {
        case OPAL_ASYNC_COMPLETION:
                rc = opal_async_wait_response(token, &msg);
                if (rc) {
                        pr_debug("Failed to wait for async response [rc=%d]\n",
                                rc);
                        break;
                }
                rc = opal_get_async_rc(msg);
                if (rc != OPAL_SUCCESS) {
                        pr_debug("OPAL async call returned failed [rc=%d]\n",
                                rc);
                        break;
                }
                break;
        case OPAL_SUCCESS:
                break;
        default:
                pr_debug("OPAL write op-panel call failed [rc=%d]\n", rc);
        }

        opal_async_release_token(token);
        return rc;
}

static ssize_t oppanel_write(struct file *filp, const char __user *userbuf,
                             size_t len, loff_t *f_pos)
{
        loff_t f_pos_prev = *f_pos;
        ssize_t ret;
        int rc;

        if (!*f_pos)
                memset(oppanel_data, ' ', oppanel_size);
        else if (*f_pos >= oppanel_size)
                return -EFBIG;

        ret = simple_write_to_buffer(oppanel_data, oppanel_size, f_pos, userbuf,
                        len);
        if (ret > 0) {
                rc = __op_panel_update_display();
                if (rc != OPAL_SUCCESS) {
                        pr_err_ratelimited("OPAL call failed to write to op panel display [rc=%d]\n",
                                rc);
                        *f_pos = f_pos_prev;
                        return -EIO;
                }
        }
        return ret;
}

static int oppanel_open(struct inode *inode, struct file *filp)
{
        if (!mutex_trylock(&oppanel_mutex)) {
                pr_debug("Device Busy\n");
                return -EBUSY;
        }
        return 0;
}

static int oppanel_release(struct inode *inode, struct file *filp)
{
        mutex_unlock(&oppanel_mutex);
        return 0;
}

static const struct file_operations oppanel_fops = {
        .owner          = THIS_MODULE,
        .llseek         = oppanel_llseek,
        .read           = oppanel_read,
        .write          = oppanel_write,
        .open           = oppanel_open,
        .release        = oppanel_release
};

static struct miscdevice oppanel_dev = {
        .minor          = MISC_DYNAMIC_MINOR,
        .name           = "op_panel",
        .fops           = &oppanel_fops
};

static int oppanel_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        u32 line_len;
        int rc, i;

        rc = of_property_read_u32(np, "#length", &line_len);
        if (rc) {
                pr_err_ratelimited("Operator panel length property not found\n");
                return rc;
        }
        rc = of_property_read_u32(np, "#lines", &num_lines);
        if (rc) {
                pr_err_ratelimited("Operator panel lines property not found\n");
                return rc;
        }
        oppanel_size = line_len * num_lines;

        pr_devel("Operator panel of size %u found with %u lines of length %u\n",
                        oppanel_size, num_lines, line_len);

        oppanel_data = kcalloc(oppanel_size, sizeof(*oppanel_data), GFP_KERNEL);
        if (!oppanel_data)
                return -ENOMEM;

        oppanel_lines = kzalloc_objs(oppanel_line_t, num_lines);
        if (!oppanel_lines) {
                rc = -ENOMEM;
                goto free_oppanel_data;
        }

        memset(oppanel_data, ' ', oppanel_size);
        for (i = 0; i < num_lines; i++) {
                oppanel_lines[i].line_len = cpu_to_be64(line_len);
                oppanel_lines[i].line = cpu_to_be64(__pa(&oppanel_data[i *
                                                line_len]));
        }

        rc = misc_register(&oppanel_dev);
        if (rc) {
                pr_err_ratelimited("Failed to register as misc device\n");
                goto free_oppanel;
        }

        return 0;

free_oppanel:
        kfree(oppanel_lines);
free_oppanel_data:
        kfree(oppanel_data);
        return rc;
}

static void oppanel_remove(struct platform_device *pdev)
{
        misc_deregister(&oppanel_dev);
        kfree(oppanel_lines);
        kfree(oppanel_data);
}

static const struct of_device_id oppanel_match[] = {
        { .compatible = "ibm,opal-oppanel" },
        { },
};

static struct platform_driver oppanel_driver = {
        .driver = {
                .name           = "powernv-op-panel",
                .of_match_table = oppanel_match,
        },
        .probe  = oppanel_probe,
        .remove = oppanel_remove,
};

module_platform_driver(oppanel_driver);

MODULE_DEVICE_TABLE(of, oppanel_match);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("PowerNV Operator Panel LCD Display Driver");
MODULE_AUTHOR("Suraj Jitindar Singh <sjitindarsingh@gmail.com>");