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Commit da4a22cb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'io-mappings-for-linus-2' of... 

Merge branch 'io-mappings-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'io-mappings-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  io mapping: clean up #ifdefs
  io mapping: improve documentation
  i915: use io-mapping interfaces instead of a variety of mapping kludges
  resources: add io-mapping functions to dynamically map large device apertures
  x86: add iomap_atomic*()/iounmap_atomic() on 32-bit using fixmaps
parents 20ebc007 e5beae16

Documentation/io-mapping.txt

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The io_mapping functions in linux/io-mapping.h provide an abstraction for

efficiently mapping small regions of an I/O device to the CPU. The initial

usage is to support the large graphics aperture on 32-bit processors where

ioremap_wc cannot be used to statically map the entire aperture to the CPU

as it would consume too much of the kernel address space.



A mapping object is created during driver initialization using



	struct io_mapping *io_mapping_create_wc(unsigned long base,

						unsigned long size)



		'base' is the bus address of the region to be made

		mappable, while 'size' indicates how large a mapping region to

		enable. Both are in bytes.



		This _wc variant provides a mapping which may only be used

		with the io_mapping_map_atomic_wc or io_mapping_map_wc.



With this mapping object, individual pages can be mapped either atomically

or not, depending on the necessary scheduling environment. Of course, atomic

maps are more efficient:



	void *io_mapping_map_atomic_wc(struct io_mapping *mapping,

				       unsigned long offset)



		'offset' is the offset within the defined mapping region.

		Accessing addresses beyond the region specified in the

		creation function yields undefined results. Using an offset

		which is not page aligned yields an undefined result. The

		return value points to a single page in CPU address space.



		This _wc variant returns a write-combining map to the

		page and may only be used with mappings created by

		io_mapping_create_wc



		Note that the task may not sleep while holding this page

		mapped.



	void io_mapping_unmap_atomic(void *vaddr)



		'vaddr' must be the the value returned by the last

		io_mapping_map_atomic_wc call. This unmaps the specified

		page and allows the task to sleep once again.



If you need to sleep while holding the lock, you can use the non-atomic

variant, although they may be significantly slower.



	void *io_mapping_map_wc(struct io_mapping *mapping,

				unsigned long offset)



		This works like io_mapping_map_atomic_wc except it allows

		the task to sleep while holding the page mapped.



	void io_mapping_unmap(void *vaddr)



		This works like io_mapping_unmap_atomic, except it is used

		for pages mapped with io_mapping_map_wc.



At driver close time, the io_mapping object must be freed:



	void io_mapping_free(struct io_mapping *mapping)



Current Implementation:



The initial implementation of these functions uses existing mapping

mechanisms and so provides only an abstraction layer and no new

functionality.



On 64-bit processors, io_mapping_create_wc calls ioremap_wc for the whole

range, creating a permanent kernel-visible mapping to the resource. The

map_atomic and map functions add the requested offset to the base of the

virtual address returned by ioremap_wc.



On 32-bit processors with HIGHMEM defined, io_mapping_map_atomic_wc uses

kmap_atomic_pfn to map the specified page in an atomic fashion;

kmap_atomic_pfn isn't really supposed to be used with device pages, but it

provides an efficient mapping for this usage.



On 32-bit processors without HIGHMEM defined, io_mapping_map_atomic_wc and

io_mapping_map_wc both use ioremap_wc, a terribly inefficient function which

performs an IPI to inform all processors about the new mapping. This results

in a significant performance penalty.

arch/x86/Kconfig

+4 −0
Original line number Original line Diff line number Diff line
@@ -1894,6 +1894,10 @@ config SYSVIPC_COMPAT 
endmenu

endmenu









config HAVE_ATOMIC_IOMAP

	def_bool y

	depends on X86_32



source "net/Kconfig"

source "net/Kconfig"





source "drivers/Kconfig"

source "drivers/Kconfig"

arch/x86/include/asm/fixmap.h

+4 −0
Original line number Original line Diff line number Diff line
@@ -9,6 +9,10 @@ 




extern int fixmaps_set;

extern int fixmaps_set;





extern pte_t *kmap_pte;

extern pgprot_t kmap_prot;

extern pte_t *pkmap_page_table;



void __native_set_fixmap(enum fixed_addresses idx, pte_t pte);

void __native_set_fixmap(enum fixed_addresses idx, pte_t pte);

void native_set_fixmap(enum fixed_addresses idx,

void native_set_fixmap(enum fixed_addresses idx,

		       unsigned long phys, pgprot_t flags);

		       unsigned long phys, pgprot_t flags);

arch/x86/include/asm/fixmap_32.h

+0 −4
Original line number Original line Diff line number Diff line
@@ -28,10 +28,8 @@ extern unsigned long __FIXADDR_TOP; 
#include <asm/acpi.h>

#include <asm/acpi.h>

#include <asm/apicdef.h>

#include <asm/apicdef.h>

#include <asm/page.h>

#include <asm/page.h>

#ifdef CONFIG_HIGHMEM

#include <linux/threads.h>

#include <linux/threads.h>

#include <asm/kmap_types.h>

#include <asm/kmap_types.h>

#endif





/*

/*

 * Here we define all the compile-time 'special' virtual

 * Here we define all the compile-time 'special' virtual
@@ -75,10 +73,8 @@ enum fixed_addresses { 
#ifdef CONFIG_X86_CYCLONE_TIMER

#ifdef CONFIG_X86_CYCLONE_TIMER

	FIX_CYCLONE_TIMER, /*cyclone timer register*/

	FIX_CYCLONE_TIMER, /*cyclone timer register*/

#endif

#endif

#ifdef CONFIG_HIGHMEM

	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */

	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */

	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,

	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,

#endif

#ifdef CONFIG_PCI_MMCONFIG

#ifdef CONFIG_PCI_MMCONFIG

	FIX_PCIE_MCFG,

	FIX_PCIE_MCFG,

#endif

#endif

arch/x86/include/asm/highmem.h

+1 −4
Original line number Original line Diff line number Diff line
@@ -25,14 +25,11 @@ 
#include <asm/kmap_types.h>

#include <asm/kmap_types.h>

#include <asm/tlbflush.h>

#include <asm/tlbflush.h>

#include <asm/paravirt.h>

#include <asm/paravirt.h>

#include <asm/fixmap.h>





/* declarations for highmem.c */

/* declarations for highmem.c */

extern unsigned long highstart_pfn, highend_pfn;

extern unsigned long highstart_pfn, highend_pfn;





extern pte_t *kmap_pte;

extern pgprot_t kmap_prot;

extern pte_t *pkmap_page_table;



/*

/*

 * Right now we initialize only a single pte table. It can be extended

 * Right now we initialize only a single pte table. It can be extended

 * easily, subsequent pte tables have to be allocated in one physical

 * easily, subsequent pte tables have to be allocated in one physical