atomicio.c

/*
 * atomicio.c - ACPI IO memory pre-mapping/post-unmapping, then
 * accessing in atomic context.
 *
 * This is used for NMI handler to access IO memory area, because
 * ioremap/iounmap can not be used in NMI handler. The IO memory area
 * is pre-mapped in process context and accessed in NMI handler.
 *
 * Copyright (C) 2009-2010, Intel Corp.
 *	Author: Huang Ying <ying.huang@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/kref.h>
#include <linux/rculist.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <acpi/atomicio.h>

#define ACPI_PFX "ACPI: "

static LIST_HEAD(acpi_iomaps);
/*
 * Used for mutual exclusion between writers of acpi_iomaps list, for
 * synchronization between readers and writer, RCU is used.
 */
static DEFINE_SPINLOCK(acpi_iomaps_lock);

struct acpi_iomap {
	struct list_head list;
	void __iomem *vaddr;
	unsigned long size;
	phys_addr_t paddr;
	struct kref ref;
};

/* acpi_iomaps_lock or RCU read lock must be held before calling */
static struct acpi_iomap *__acpi_find_iomap(phys_addr_t paddr,
					    unsigned long size)
{
	struct acpi_iomap *map;

	list_for_each_entry_rcu(map, &acpi_iomaps, list) {
		if (map->paddr + map->size >= paddr + size &&
		    map->paddr <= paddr)
			return map;
	}
	return NULL;
}

/*
 * Atomic "ioremap" used by NMI handler, if the specified IO memory
 * area is not pre-mapped, NULL will be returned.
 *
 * acpi_iomaps_lock or RCU read lock must be held before calling
 */
static void __iomem *__acpi_ioremap_fast(phys_addr_t paddr,
					 unsigned long size)
{
	struct acpi_iomap *map;

	map = __acpi_find_iomap(paddr, size);
	if (map)
		return map->vaddr + (paddr - map->paddr);
	else
		return NULL;
}

/* acpi_iomaps_lock must be held before calling */
static void __iomem *__acpi_try_ioremap(phys_addr_t paddr,
					unsigned long size)
{
	struct acpi_iomap *map;

	map = __acpi_find_iomap(paddr, size);
	if (map) {
		kref_get(&map->ref);
		return map->vaddr + (paddr - map->paddr);
	} else
		return NULL;
}

/*
 * Used to pre-map the specified IO memory area. First try to find
 * whether the area is already pre-mapped, if it is, increase the
 * reference count (in __acpi_try_ioremap) and return; otherwise, do
 * the real ioremap, and add the mapping into acpi_iomaps list.
 */
static void __iomem *acpi_pre_map(phys_addr_t paddr,
				  unsigned long size)
{
	void __iomem *vaddr;
	struct acpi_iomap *map;
	unsigned long pg_sz, flags;
	phys_addr_t pg_off;

	spin_lock_irqsave(&acpi_iomaps_lock, flags);
	vaddr = __acpi_try_ioremap(paddr, size);
	spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
	if (vaddr)
		return vaddr;

	pg_off = paddr & PAGE_MASK;
	pg_sz = ((paddr + size + PAGE_SIZE - 1) & PAGE_MASK) - pg_off;
	vaddr = ioremap(pg_off, pg_sz);
	if (!vaddr)
		return NULL;
	map = kmalloc(sizeof(*map), GFP_KERNEL);
	if (!map)
		goto err_unmap;
	INIT_LIST_HEAD(&map->list);
	map->paddr = pg_off;
	map->size = pg_sz;
	map->vaddr = vaddr;
	kref_init(&map->ref);

	spin_lock_irqsave(&acpi_iomaps_lock, flags);
	vaddr = __acpi_try_ioremap(paddr, size);
	if (vaddr) {
		spin_unlock_irqrestore(&acpi_iomaps_lock, flags);
		iounmap(map->vaddr);
		kfree(map);
		return vaddr;
	}
	list_add_tail_rcu(&map->list, &acpi_iomaps);
	spin_unlock_irqrestore(&acpi_iomaps_lock, flags);

	return map->vaddr + (paddr - map->paddr);
err_unmap:
	iounmap(vaddr);
	return NULL;
}

/* acpi_iomaps_lock must be held before calling */
static void __acpi_kref_del_iomap(struct kref *ref)
{
	struct acpi_iomap *map;

	map = container_of(ref, struct acpi_iomap, ref);
	list_del_rcu(&map->list);
}

/*
 * Used to post-unmap the specified IO memory area. The iounmap is
 * done only if the reference count goes zero.
 */
static void acpi_post_unmap(phys_addr_t paddr, unsigned long size)
{
	struct acpi_iomap *map;
	unsigned long flags;
	int del;

	spin_lock_irqsave(&acpi_iomaps_lock, flags);
	map = __acpi_find_iomap(paddr, size);
	BUG_ON(!map);
	del = kref_put(&map->ref, __acpi_kref_del_iomap);
	spin_unlock_irqrestore(&acpi_iomaps_lock, flags);

	if (!del)
		return;

	synchronize_rcu();
	iounmap(map->vaddr);
	kfree(map);
}

/* In NMI handler, should set silent = 1 */
static int acpi_check_gar(struct acpi_generic_address *reg,
			  u64 *paddr, int silent)
{
	u32 width, space_id;

	width = reg->bit_width;
	space_id = reg->space_id;
	/* Handle possible alignment issues */
	memcpy(paddr, &reg->address, sizeof(*paddr));
	if (!*paddr) {
		if (!silent)
			pr_warning(FW_BUG ACPI_PFX
			"Invalid physical address in GAR [0x%llx/%u/%u]\n",
				   *paddr, width, space_id);
		return -EINVAL;
	}

	if ((width != 8) && (width != 16) && (width != 32) && (width != 64)) {
		if (!silent)
			pr_warning(FW_BUG ACPI_PFX
				   "Invalid bit width in GAR [0x%llx/%u/%u]\n",
				   *paddr, width, space_id);
		return -EINVAL;
	}

	if (space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY &&
	    space_id != ACPI_ADR_SPACE_SYSTEM_IO) {
		if (!silent)
			pr_warning(FW_BUG ACPI_PFX
			"Invalid address space type in GAR [0x%llx/%u/%u]\n",
				   *paddr, width, space_id);
		return -EINVAL;
	}

	return 0;
}

/* Pre-map, working on GAR */
int acpi_pre_map_gar(struct acpi_generic_address *reg)
{
	u64 paddr;
	void __iomem *vaddr;
	int rc;

	if (reg->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
		return 0;

	rc = acpi_check_gar(reg, &paddr, 0);
	if (rc)
		return rc;

	vaddr = acpi_pre_map(paddr, reg->bit_width / 8);
	if (!vaddr)
		return -EIO;

	return 0;
}
EXPORT_SYMBOL_GPL(acpi_pre_map_gar);

/* Post-unmap, working on GAR */
int acpi_post_unmap_gar(struct acpi_generic_address *reg)
{
	u64 paddr;
	int rc;

	if (reg->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
		return 0;

	rc = acpi_check_gar(reg, &paddr, 0);
	if (rc)
		return rc;

	acpi_post_unmap(paddr, reg->bit_width / 8);

	return 0;
}
EXPORT_SYMBOL_GPL(acpi_post_unmap_gar);

/*
 * Can be used in atomic (including NMI) or process context. RCU read
 * lock can only be released after the IO memory area accessing.
 */
static int acpi_atomic_read_mem(u64 paddr, u64 *val, u32 width)
{
	void __iomem *addr;

	rcu_read_lock();
	addr = __acpi_ioremap_fast(paddr, width);
	switch (width) {
	case 8:
		*val = readb(addr);
		break;
	case 16:
		*val = readw(addr);
		break;
	case 32:
		*val = readl(addr);
		break;
	case 64:
		*val = readq(addr);
		break;
	default:
		return -EINVAL;
	}
	rcu_read_unlock();

	return 0;
}

static int acpi_atomic_write_mem(u64 paddr, u64 val, u32 width)
{
	void __iomem *addr;

	rcu_read_lock();
	addr = __acpi_ioremap_fast(paddr, width);
	switch (width) {
	case 8:
		writeb(val, addr);
		break;
	case 16:
		writew(val, addr);
		break;
	case 32:
		writel(val, addr);
		break;
	case 64:
		writeq(val, addr);
		break;
	default:
		return -EINVAL;
	}
	rcu_read_unlock();

	return 0;
}

/* GAR accessing in atomic (including NMI) or process context */
int acpi_atomic_read(u64 *val, struct acpi_generic_address *reg)
{
	u64 paddr;
	int rc;

	rc = acpi_check_gar(reg, &paddr, 1);
	if (rc)
		return rc;

	*val = 0;
	switch (reg->space_id) {
	case ACPI_ADR_SPACE_SYSTEM_MEMORY:
		return acpi_atomic_read_mem(paddr, val, reg->bit_width);
	case ACPI_ADR_SPACE_SYSTEM_IO:
		return acpi_os_read_port(paddr, (u32 *)val, reg->bit_width);
	default:
		return -EINVAL;
	}
}
EXPORT_SYMBOL_GPL(acpi_atomic_read);

int acpi_atomic_write(u64 val, struct acpi_generic_address *reg)
{
	u64 paddr;
	int rc;

	rc = acpi_check_gar(reg, &paddr, 1);
	if (rc)
		return rc;

	switch (reg->space_id) {
	case ACPI_ADR_SPACE_SYSTEM_MEMORY:
		return acpi_atomic_write_mem(paddr, val, reg->bit_width);
	case ACPI_ADR_SPACE_SYSTEM_IO:
		return acpi_os_write_port(paddr, val, reg->bit_width);
	default:
		return -EINVAL;
	}
}
EXPORT_SYMBOL_GPL(acpi_atomic_write);