ilsel.c

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/*
 * arch/sh/boards/mach-x3proto/ilsel.c
 *
 * Helper routines for SH-X3 proto board ILSEL.
 *
 * Copyright (C) 2007 - 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) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bitmap.h>
#include <linux/io.h>
#include <mach/ilsel.h>

/*
 * ILSEL is split across:
 *
 *  ILSEL0 - 0xb8100004 [ Levels  1 -  4 ]
 *  ILSEL1 - 0xb8100006 [ Levels  5 -  8 ]
 *  ILSEL2 - 0xb8100008 [ Levels  9 - 12 ]
 *  ILSEL3 - 0xb810000a [ Levels 13 - 15 ]
 *
 * With each level being relative to an ilsel_source_t.
 */
#define ILSEL_BASE  0xb8100004
#define ILSEL_LEVELS    15

/*
 * ILSEL level map, in descending order from the highest level down.
 *
 * Supported levels are 1 - 15 spread across ILSEL0 - ILSEL4, mapping
 * directly to IRLs. As the IRQs are numbered in reverse order relative
 * to the interrupt level, the level map is carefully managed to ensure a
 * 1:1 mapping between the bit position and the IRQ number.
 *
 * This careful constructions allows ilsel_enable*() to be referenced
 * directly for hooking up an ILSEL set and getting back an IRQ which can
 * subsequently be used for internal accounting in the (optional) disable
 * path.
 */
static unsigned long ilsel_level_map;

static inline unsigned int ilsel_offset(unsigned int bit)
{
    return ILSEL_LEVELS - bit - 1;
}

static inline unsigned long mk_ilsel_addr(unsigned int bit)
{
    return ILSEL_BASE + ((ilsel_offset(bit) >> 1) & ~0x1);
}

static inline unsigned int mk_ilsel_shift(unsigned int bit)
{
    return (ilsel_offset(bit) & 0x3) << 2;
}

static void __ilsel_enable(ilsel_source_t set, unsigned int bit)
{
    unsigned int tmp, shift;
    unsigned long addr;

    pr_notice("enabling ILSEL set %d\n", set);

    addr = mk_ilsel_addr(bit);
    shift = mk_ilsel_shift(bit);

    pr_debug("%s: bit#%d: addr - 0x%08lx (shift %d, set %d)\n",
         __func__, bit, addr, shift, set);

    tmp = __raw_readw(addr);
    tmp &= ~(0xf << shift);
    tmp |= set << shift;
    __raw_writew(tmp, addr);
}

int ilsel_enable(ilsel_source_t set)
{
    unsigned int bit;

    if (unlikely(set > ILSEL_KEY)) {
        pr_err("Aliased sources must use ilsel_enable_fixed()\n");
        return -EINVAL;
    }

    do {
        bit = find_first_zero_bit(&ilsel_level_map, ILSEL_LEVELS);
    } while (test_and_set_bit(bit, &ilsel_level_map));

    __ilsel_enable(set, bit);

    return bit;
}
EXPORT_SYMBOL_GPL(ilsel_enable);

int ilsel_enable_fixed(ilsel_source_t set, unsigned int level)
{
    unsigned int bit = ilsel_offset(level - 1);

    if (test_and_set_bit(bit, &ilsel_level_map))
        return -EBUSY;

    __ilsel_enable(set, bit);

    return bit;
}
EXPORT_SYMBOL_GPL(ilsel_enable_fixed);

void ilsel_disable(unsigned int irq)
{
    unsigned long addr;
    unsigned int tmp;

    pr_notice("disabling ILSEL set %d\n", irq);

    addr = mk_ilsel_addr(irq);

    tmp = __raw_readw(addr);
    tmp &= ~(0xf << mk_ilsel_shift(irq));
    __raw_writew(tmp, addr);

    clear_bit(irq, &ilsel_level_map);
}
EXPORT_SYMBOL_GPL(ilsel_disable);