/*
 * Support for hardware-assisted userspace interrupt masking.
 *
 * Copyright (C) 2010  Paul Mundt
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#define pr_fmt(fmt) "intc: " fmt

#include <linux/errno.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/stat.h>
#include <linux/sizes.h>
#include "internals.h"

static void __iomem *uimask;

static ssize_t
show_intc_userimask(struct device *dev,
                    struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", (__raw_readl(uimask) >> 4) & 0xf);
}

static ssize_t
store_intc_userimask(struct device *dev,
                     struct device_attribute *attr,
                     const char *buf, size_t count)
{
        unsigned long level;
        int ret;

        ret = kstrtoul(buf, 10, &level);
        if (ret != 0)
                return ret;

        /*
         * Minimal acceptable IRQ levels are in the 2 - 16 range, but
         * these are chomped so as to not interfere with normal IRQs.
         *
         * Level 1 is a special case on some CPUs in that it's not
         * directly settable, but given that USERIMASK cuts off below a
         * certain level, we don't care about this limitation here.
         * Level 0 on the other hand equates to user masking disabled.
         *
         * We use the default priority level as a cut off so that only
         * special case opt-in IRQs can be mangled.
         */
        if (level >= intc_get_dfl_prio_level())
                return -EINVAL;

        __raw_writel(0xa5 << 24 | level << 4, uimask);

        return count;
}

static DEVICE_ATTR(userimask, S_IRUSR | S_IWUSR,
                   show_intc_userimask, store_intc_userimask);


static int __init userimask_sysdev_init(void)
{
        struct device *dev_root;
        int ret = 0;

        if (unlikely(!uimask))
                return -ENXIO;

        dev_root = bus_get_dev_root(&intc_subsys);
        if (dev_root) {
                ret = device_create_file(dev_root, &dev_attr_userimask);
                put_device(dev_root);
        }
        return ret;
}
late_initcall(userimask_sysdev_init);

int register_intc_userimask(unsigned long addr)
{
        if (unlikely(uimask))
                return -EBUSY;

        uimask = ioremap(addr, SZ_4K);
        if (unlikely(!uimask))
                return -ENOMEM;

        pr_info("userimask support registered for levels 0 -> %d\n",
                intc_get_dfl_prio_level() - 1);

        return 0;
}