userimask.c

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/*
 * 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 <asm/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;

    level = simple_strtoul(buf, NULL, 10);

    /*
     * 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)
{
    if (unlikely(!uimask))
        return -ENXIO;

    return device_create_file(intc_subsys.dev_root, &dev_attr_userimask);
}
late_initcall(userimask_sysdev_init);

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

    uimask = ioremap_nocache(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;
}