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resources: add io-mapping functions to dynamically map large device apertures

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Impact: add new generic io_map_*() APIs

Graphics devices have large PCI apertures which would consume a significant
fraction of a 32-bit address space if mapped during driver initialization.
Using ioremap at runtime is impractical as it is too slow.

This new set of interfaces uses atomic mappings on 32-bit processors and a
large static mapping on 64-bit processors to provide reasonable 32-bit
performance and optimal 64-bit performance.

The current implementation sits atop the io_map_atomic fixmap-based
mechanism for 32-bit processors.

This includes some editorial suggestions from Randy Dunlap for
Documentation/io-mapping.txt

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Keith Packard 2008-10-30 19:38:18 -07:00 • committed by Ingo Molnar
parent fd94093435
commit 9663f2e6a6
2 changed files with 194 additions and 0 deletions
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118
include/linux/io-mapping.h Normal file
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/*
* Copyright © 2008 Keith Packard <keithp@keithp.com>
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef _LINUX_IO_MAPPING_H
#define _LINUX_IO_MAPPING_H
#include <linux/types.h>
#include <asm/io.h>
#include <asm/page.h>
#include <asm/iomap.h>
/*
* The io_mapping mechanism provides an abstraction for mapping
* individual pages from an io device to the CPU in an efficient fashion.
*
* See Documentation/io_mapping.txt
*/
/* this struct isn't actually defined anywhere */
struct io_mapping;
#ifdef CONFIG_X86_64
/* Create the io_mapping object*/
static inline struct io_mapping *
io_mapping_create_wc(unsigned long base, unsigned long size)
{
return (struct io_mapping *) ioremap_wc(base, size);
}
static inline void
io_mapping_free(struct io_mapping *mapping)
{
iounmap(mapping);
}
/* Atomic map/unmap */
static inline void *
io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
{
return ((char *) mapping) + offset;
}
static inline void
io_mapping_unmap_atomic(void *vaddr)
{
}
/* Non-atomic map/unmap */
static inline void *
io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
{
return ((char *) mapping) + offset;
}
static inline void
io_mapping_unmap(void *vaddr)
{
}
#endif /* CONFIG_X86_64 */
#ifdef CONFIG_X86_32
static inline struct io_mapping *
io_mapping_create_wc(unsigned long base, unsigned long size)
{
return (struct io_mapping *) base;
}
static inline void
io_mapping_free(struct io_mapping *mapping)
{
}
/* Atomic map/unmap */
static inline void *
io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
{
offset += (unsigned long) mapping;
return iomap_atomic_prot_pfn(offset >> PAGE_SHIFT, KM_USER0,
__pgprot(__PAGE_KERNEL_WC));
}
static inline void
io_mapping_unmap_atomic(void *vaddr)
{
iounmap_atomic(vaddr, KM_USER0);
}
static inline void *
io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
{
offset += (unsigned long) mapping;
return ioremap_wc(offset, PAGE_SIZE);
}
static inline void
io_mapping_unmap(void *vaddr)
{
iounmap(vaddr);
}
#endif /* CONFIG_X86_32 */
#endif /* _LINUX_IO_MAPPING_H */