/*
 * Copyright 2017 IBM Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/mfd/syscon.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/poll.h>
#include <linux/regmap.h>

#include <linux/aspeed-lpc-ctrl.h>

#define DEVICE_NAME     "aspeed-lpc-ctrl"

#define HICR7 0x8
#define HICR8 0xc

struct aspeed_lpc_ctrl {
        struct miscdevice       miscdev;
        struct regmap           *regmap;
        phys_addr_t             mem_base;
        resource_size_t         mem_size;
        u32             pnor_size;
        u32             pnor_base;
};

static struct aspeed_lpc_ctrl *file_aspeed_lpc_ctrl(struct file *file)
{
        return container_of(file->private_data, struct aspeed_lpc_ctrl,
                        miscdev);
}

static int aspeed_lpc_ctrl_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct aspeed_lpc_ctrl *lpc_ctrl = file_aspeed_lpc_ctrl(file);
        unsigned long vsize = vma->vm_end - vma->vm_start;
        pgprot_t prot = vma->vm_page_prot;

        if (vma->vm_pgoff + vsize > lpc_ctrl->mem_base + lpc_ctrl->mem_size)
                return -EINVAL;

        /* ast2400/2500 AHB accesses are not cache coherent */
        prot = pgprot_noncached(prot);

        if (remap_pfn_range(vma, vma->vm_start,
                (lpc_ctrl->mem_base >> PAGE_SHIFT) + vma->vm_pgoff,
                vsize, prot))
                return -EAGAIN;

        return 0;
}

static long aspeed_lpc_ctrl_ioctl(struct file *file, unsigned int cmd,
                unsigned long param)
{
        struct aspeed_lpc_ctrl *lpc_ctrl = file_aspeed_lpc_ctrl(file);
        void __user *p = (void __user *)param;
        struct aspeed_lpc_ctrl_mapping map;
        u32 addr;
        u32 size;
        long rc;

        if (copy_from_user(&map, p, sizeof(map)))
                return -EFAULT;

        if (map.flags != 0)
                return -EINVAL;

        switch (cmd) {
        case ASPEED_LPC_CTRL_IOCTL_GET_SIZE:
                /* The flash windows don't report their size */
                if (map.window_type != ASPEED_LPC_CTRL_WINDOW_MEMORY)
                        return -EINVAL;

                /* Support more than one window id in the future */
                if (map.window_id != 0)
                        return -EINVAL;

                map.size = lpc_ctrl->mem_size;

                return copy_to_user(p, &map, sizeof(map)) ? -EFAULT : 0;
        case ASPEED_LPC_CTRL_IOCTL_MAP:

                /*
                 * The top half of HICR7 is the MSB of the BMC address of the
                 * mapping.
                 * The bottom half of HICR7 is the MSB of the HOST LPC
                 * firmware space address of the mapping.
                 *
                 * The 1 bits in the top of half of HICR8 represent the bits
                 * (in the requested address) that should be ignored and
                 * replaced with those from the top half of HICR7.
                 * The 1 bits in the bottom half of HICR8 represent the bits
                 * (in the requested address) that should be kept and pass
                 * into the BMC address space.
                 */

                /*
                 * It doesn't make sense to talk about a size or offset with
                 * low 16 bits set. Both HICR7 and HICR8 talk about the top 16
                 * bits of addresses and sizes.
                 */

                if ((map.size & 0x0000ffff) || (map.offset & 0x0000ffff))
                        return -EINVAL;

                /*
                 * Because of the way the masks work in HICR8 offset has to
                 * be a multiple of size.
                 */
                if (map.offset & (map.size - 1))
                        return -EINVAL;

                if (map.window_type == ASPEED_LPC_CTRL_WINDOW_FLASH) {
                        addr = lpc_ctrl->pnor_base;
                        size = lpc_ctrl->pnor_size;
                } else if (map.window_type == ASPEED_LPC_CTRL_WINDOW_MEMORY) {
                        addr = lpc_ctrl->mem_base;
                        size = lpc_ctrl->mem_size;
                } else {
                        return -EINVAL;
                }

                /* Check overflow first! */
                if (map.offset + map.size < map.offset ||
                        map.offset + map.size > size)
                        return -EINVAL;

                if (map.size == 0 || map.size > size)
                        return -EINVAL;

                addr += map.offset;

                /*
                 * addr (host lpc address) is safe regardless of values. This
                 * simply changes the address the host has to request on its
                 * side of the LPC bus. This cannot impact the hosts own
                 * memory space by surprise as LPC specific accessors are
                 * required. The only strange thing that could be done is
                 * setting the lower 16 bits but the shift takes care of that.
                 */

                rc = regmap_write(lpc_ctrl->regmap, HICR7,
                                (addr | (map.addr >> 16)));
                if (rc)
                        return rc;

                return regmap_write(lpc_ctrl->regmap, HICR8,
                        (~(map.size - 1)) | ((map.size >> 16) - 1));
        }

        return -EINVAL;
}

static const struct file_operations aspeed_lpc_ctrl_fops = {
        .owner          = THIS_MODULE,
        .mmap           = aspeed_lpc_ctrl_mmap,
        .unlocked_ioctl = aspeed_lpc_ctrl_ioctl,
};

static int aspeed_lpc_ctrl_probe(struct platform_device *pdev)
{
        struct aspeed_lpc_ctrl *lpc_ctrl;
        struct device_node *node;
        struct resource resm;
        struct device *dev;
        int rc;

        dev = &pdev->dev;

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

        node = of_parse_phandle(dev->of_node, "flash", 0);
        if (!node) {
                dev_err(dev, "Didn't find host pnor flash node\n");
                return -ENODEV;
        }

        rc = of_address_to_resource(node, 1, &resm);
        of_node_put(node);
        if (rc) {
                dev_err(dev, "Couldn't address to resource for flash\n");
                return rc;
        }

        lpc_ctrl->pnor_size = resource_size(&resm);
        lpc_ctrl->pnor_base = resm.start;

        dev_set_drvdata(&pdev->dev, lpc_ctrl);

        node = of_parse_phandle(dev->of_node, "memory-region", 0);
        if (!node) {
                dev_err(dev, "Didn't find reserved memory\n");
                return -EINVAL;
        }

        rc = of_address_to_resource(node, 0, &resm);
        of_node_put(node);
        if (rc) {
                dev_err(dev, "Couldn't address to resource for reserved memory\n");
                return -ENOMEM;
        }

        lpc_ctrl->mem_size = resource_size(&resm);
        lpc_ctrl->mem_base = resm.start;

        lpc_ctrl->regmap = syscon_node_to_regmap(
                        pdev->dev.parent->of_node);
        if (IS_ERR(lpc_ctrl->regmap)) {
                dev_err(dev, "Couldn't get regmap\n");
                return -ENODEV;
        }

        lpc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
        lpc_ctrl->miscdev.name = DEVICE_NAME;
        lpc_ctrl->miscdev.fops = &aspeed_lpc_ctrl_fops;
        lpc_ctrl->miscdev.parent = dev;
        rc = misc_register(&lpc_ctrl->miscdev);
        if (rc)
                dev_err(dev, "Unable to register device\n");
        else
                dev_info(dev, "Loaded at %pr\n", &resm);

        return rc;
}

static int aspeed_lpc_ctrl_remove(struct platform_device *pdev)
{
        struct aspeed_lpc_ctrl *lpc_ctrl = dev_get_drvdata(&pdev->dev);

        misc_deregister(&lpc_ctrl->miscdev);

        return 0;
}

static const struct of_device_id aspeed_lpc_ctrl_match[] = {
        { .compatible = "aspeed,ast2400-lpc-ctrl" },
        { .compatible = "aspeed,ast2500-lpc-ctrl" },
        { },
};

static struct platform_driver aspeed_lpc_ctrl_driver = {
        .driver = {
                .name           = DEVICE_NAME,
                .of_match_table = aspeed_lpc_ctrl_match,
        },
        .probe = aspeed_lpc_ctrl_probe,
        .remove = aspeed_lpc_ctrl_remove,
};

module_platform_driver(aspeed_lpc_ctrl_driver);

MODULE_DEVICE_TABLE(of, aspeed_lpc_ctrl_match);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Cyril Bur <cyrilbur@gmail.com>");
MODULE_DESCRIPTION("Control for aspeed 2400/2500 LPC HOST to BMC mappings");