iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arch/*/: remove CONFIG_VIRT_TO_BUS

Browse Source 
All architecture-independent users of virt_to_bus() and bus_to_virt()
have been fixed to use the dma mapping interfaces or have been
removed now.  This means the definitions on most architectures, and the
CONFIG_VIRT_TO_BUS symbol are now obsolete and can be removed.

The only exceptions to this are a few network and scsi drivers for m68k
Amiga and VME machines and ppc32 Macintosh. These drivers work correctly
with the old interfaces and are probably not worth changing.

On alpha and parisc, virt_to_bus() were still used in asm/floppy.h.
alpha can use isa_virt_to_bus() like x86 does, and parisc can just
open-code the virt_to_phys() here, as this is architecture specific
code.

I tried updating the bus-virt-phys-mapping.rst documentation, which
started as an email from Linus to explain some details of the Linux-2.0
driver interfaces. The bits about virt_to_bus() were declared obsolete
backin 2000, and the rest is not all that relevant any more, so in the
end I just decided to remove the file completely.

Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann 2022-05-23 21:59:02 +02:00
parent 93929fb6c4
commit 4313a24985
27 changed files with 10 additions and 311 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

220
Documentation/core-api/bus-virt-phys-mapping.rst
View File

@ -1,220 +0,0 @@
==========================================================
How to access I/O mapped memory from within device drivers
==========================================================
:Author: Linus
.. warning::
The virt_to_bus() and bus_to_virt() functions have been
superseded by the functionality provided by the PCI DMA interface
(see Documentation/core-api/dma-api-howto.rst). They continue
to be documented below for historical purposes, but new code
must not use them. --davidm 00/12/12
::
[ This is a mail message in response to a query on IO mapping, thus the
strange format for a "document" ]
The AHA-1542 is a bus-master device, and your patch makes the driver give the
controller the physical address of the buffers, which is correct on x86
(because all bus master devices see the physical memory mappings directly).
However, on many setups, there are actually **three** different ways of looking
at memory addresses, and in this case we actually want the third, the
so-called "bus address".
Essentially, the three ways of addressing memory are (this is "real memory",
that is, normal RAM--see later about other details):
- CPU untranslated. This is the "physical" address. Physical address
0 is what the CPU sees when it drives zeroes on the memory bus.
- CPU translated address. This is the "virtual" address, and is
completely internal to the CPU itself with the CPU doing the appropriate
translations into "CPU untranslated".
- bus address. This is the address of memory as seen by OTHER devices,
not the CPU. Now, in theory there could be many different bus
addresses, with each device seeing memory in some device-specific way, but
happily most hardware designers aren't actually actively trying to make
things any more complex than necessary, so you can assume that all
external hardware sees the memory the same way.
Now, on normal PCs the bus address is exactly the same as the physical
address, and things are very simple indeed. However, they are that simple
because the memory and the devices share the same address space, and that is
not generally necessarily true on other PCI/ISA setups.
Now, just as an example, on the PReP (PowerPC Reference Platform), the
CPU sees a memory map something like this (this is from memory)::
0-2 GB "real memory"
2 GB-3 GB "system IO" (inb/out and similar accesses on x86)
3 GB-4 GB "IO memory" (shared memory over the IO bus)
Now, that looks simple enough. However, when you look at the same thing from
the viewpoint of the devices, you have the reverse, and the physical memory
address 0 actually shows up as address 2 GB for any IO master.
So when the CPU wants any bus master to write to physical memory 0, it
has to give the master address 0x80000000 as the memory address.
So, for example, depending on how the kernel is actually mapped on the
PPC, you can end up with a setup like this::
physical address: 0
virtual address: 0xC0000000
bus address: 0x80000000
where all the addresses actually point to the same thing. It's just seen
through different translations..
Similarly, on the Alpha, the normal translation is::
physical address: 0
virtual address: 0xfffffc0000000000
bus address: 0x40000000
(but there are also Alphas where the physical address and the bus address
are the same).
Anyway, the way to look up all these translations, you do::
#include <asm/io.h>
phys_addr = virt_to_phys(virt_addr);
virt_addr = phys_to_virt(phys_addr);
bus_addr = virt_to_bus(virt_addr);
virt_addr = bus_to_virt(bus_addr);
Now, when do you need these?
You want the **virtual** address when you are actually going to access that
pointer from the kernel. So you can have something like this::
/*
* this is the hardware "mailbox" we use to communicate with
* the controller. The controller sees this directly.
*/
struct mailbox {
__u32 status;
__u32 bufstart;
__u32 buflen;
..
} mbox;
unsigned char * retbuffer;
/* get the address from the controller */
retbuffer = bus_to_virt(mbox.bufstart);
switch (retbuffer[0]) {
case STATUS_OK:
...
on the other hand, you want the bus address when you have a buffer that
you want to give to the controller::
/* ask the controller to read the sense status into "sense_buffer" */
mbox.bufstart = virt_to_bus(&sense_buffer);
mbox.buflen = sizeof(sense_buffer);
mbox.status = 0;
notify_controller(&mbox);
And you generally **never** want to use the physical address, because you can't
use that from the CPU (the CPU only uses translated virtual addresses), and
you can't use it from the bus master.
So why do we care about the physical address at all? We do need the physical
address in some cases, it's just not very often in normal code. The physical
address is needed if you use memory mappings, for example, because the
"remap_pfn_range()" mm function wants the physical address of the memory to
be remapped as measured in units of pages, a.k.a. the pfn (the memory
management layer doesn't know about devices outside the CPU, so it
shouldn't need to know about "bus addresses" etc).
.. note::
The above is only one part of the whole equation. The above
only talks about "real memory", that is, CPU memory (RAM).
There is a completely different type of memory too, and that's the "shared
memory" on the PCI or ISA bus. That's generally not RAM (although in the case
of a video graphics card it can be normal DRAM that is just used for a frame
buffer), but can be things like a packet buffer in a network card etc.
This memory is called "PCI memory" or "shared memory" or "IO memory" or
whatever, and there is only one way to access it: the readb/writeb and
related functions. You should never take the address of such memory, because
there is really nothing you can do with such an address: it's not
conceptually in the same memory space as "real memory" at all, so you cannot
just dereference a pointer. (Sadly, on x86 it **is** in the same memory space,
so on x86 it actually works to just deference a pointer, but it's not
portable).
For such memory, you can do things like:
- reading::
/*
* read first 32 bits from ISA memory at 0xC0000, aka
* C000:0000 in DOS terms
*/
unsigned int signature = isa_readl(0xC0000);
- remapping and writing::
/*
* remap framebuffer PCI memory area at 0xFC000000,
* size 1MB, so that we can access it: We can directly
* access only the 640k-1MB area, so anything else
* has to be remapped.
*/
void __iomem *baseptr = ioremap(0xFC000000, 1024*1024);
/* write a 'A' to the offset 10 of the area */
writeb('A',baseptr+10);
/* unmap when we unload the driver */
iounmap(baseptr);
- copying and clearing::
/* get the 6-byte Ethernet address at ISA address E000:0040 */
memcpy_fromio(kernel_buffer, 0xE0040, 6);
/* write a packet to the driver */
memcpy_toio(0xE1000, skb->data, skb->len);
/* clear the frame buffer */
memset_io(0xA0000, 0, 0x10000);
OK, that just about covers the basics of accessing IO portably. Questions?
Comments? You may think that all the above is overly complex, but one day you
might find yourself with a 500 MHz Alpha in front of you, and then you'll be
happy that your driver works ;)
Note that kernel versions 2.0.x (and earlier) mistakenly called the
ioremap() function "vremap()". ioremap() is the proper name, but I
didn't think straight when I wrote it originally. People who have to
support both can do something like::
/* support old naming silliness */
#if LINUX_VERSION_CODE < 0x020100
#define ioremap vremap
#define iounmap vfree
#endif
at the top of their source files, and then they can use the right names
even on 2.0.x systems.
And the above sounds worse than it really is. Most real drivers really
don't do all that complex things (or rather: the complexity is not so
much in the actual IO accesses as in error handling and timeouts etc).
It's generally not hard to fix drivers, and in many cases the code
actually looks better afterwards::
unsigned long signature = *(unsigned int *) 0xC0000;
vs
unsigned long signature = readl(0xC0000);
I think the second version actually is more readable, no?

14
Documentation/core-api/dma-api-howto.rst
View File

@ -707,20 +707,6 @@ to use the dma_sync_*() interfaces::
}
}
Drivers converted fully to this interface should not use virt_to_bus() any
longer, nor should they use bus_to_virt(). Some drivers have to be changed a
little bit, because there is no longer an equivalent to bus_to_virt() in the
dynamic DMA mapping scheme - you have to always store the DMA addresses
returned by the dma_alloc_coherent(), dma_pool_alloc(), and dma_map_single()
calls (dma_map_sg() stores them in the scatterlist itself if the platform
supports dynamic DMA mapping in hardware) in your driver structures and/or
in the card registers.
All drivers should be using these interfaces with no exceptions. It
is planned to completely remove virt_to_bus() and bus_to_virt() as
they are entirely deprecated. Some ports already do not provide these
as it is impossible to correctly support them.
Handling Errors
===============

1
Documentation/core-api/index.rst
View File

@ -41,7 +41,6 @@ Library functionality that is used throughout the kernel.
rbtree
generic-radix-tree
packing
bus-virt-phys-mapping
this_cpu_ops
timekeeping
errseq

1
Documentation/translations/zh_CN/core-api/index.rst
View File

@ -52,7 +52,6 @@ Todolist:
circular-buffers
generic-radix-tree
packing
bus-virt-phys-mapping
this_cpu_ops
timekeeping
errseq

1
arch/alpha/Kconfig
View File

@ -17,7 +17,6 @@ config ALPHA
select HAVE_PERF_EVENTS
select NEED_DMA_MAP_STATE
select NEED_SG_DMA_LENGTH
select VIRT_TO_BUS
select GENERIC_IRQ_PROBE
select GENERIC_PCI_IOMAP
select AUTO_IRQ_AFFINITY if SMP

2
arch/alpha/include/asm/floppy.h
View File

@ -20,7 +20,7 @@
#define fd_free_dma() free_dma(FLOPPY_DMA)
#define fd_clear_dma_ff() clear_dma_ff(FLOPPY_DMA)
#define fd_set_dma_mode(mode) set_dma_mode(FLOPPY_DMA,mode)
#define fd_set_dma_addr(addr) set_dma_addr(FLOPPY_DMA,virt_to_bus(addr))
#define fd_set_dma_addr(addr) set_dma_addr(FLOPPY_DMA,isa_virt_to_bus(addr))
#define fd_set_dma_count(count) set_dma_count(FLOPPY_DMA,count)
#define fd_enable_irq() enable_irq(FLOPPY_IRQ)
#define fd_disable_irq() disable_irq(FLOPPY_IRQ)

8
arch/alpha/include/asm/io.h
View File

@ -106,15 +106,15 @@ static inline void * phys_to_virt(unsigned long address)
extern unsigned long __direct_map_base;
extern unsigned long __direct_map_size;
static inline unsigned long __deprecated virt_to_bus(volatile void *address)
static inline unsigned long __deprecated isa_virt_to_bus(volatile void *address)
{
unsigned long phys = virt_to_phys(address);
unsigned long bus = phys + __direct_map_base;
return phys <= __direct_map_size ? bus : 0;
}
#define isa_virt_to_bus virt_to_bus
#define isa_virt_to_bus isa_virt_to_bus
static inline void * __deprecated bus_to_virt(unsigned long address)
static inline void * __deprecated isa_bus_to_virt(unsigned long address)
{
void *virt;
@ -125,7 +125,7 @@ static inline void * __deprecated bus_to_virt(unsigned long address)
virt = phys_to_virt(address);
return (long)address <= 0 ? NULL : virt;
}
#define isa_bus_to_virt bus_to_virt
#define isa_bus_to_virt isa_bus_to_virt
/*
* There are different chipsets to interface the Alpha CPUs to the world.

1
arch/ia64/Kconfig
View File

@ -39,7 +39,6 @@ config IA64
select HAVE_FUNCTION_DESCRIPTORS
select HAVE_VIRT_CPU_ACCOUNTING
select HUGETLB_PAGE_SIZE_VARIABLE if HUGETLB_PAGE
select VIRT_TO_BUS
select GENERIC_IRQ_PROBE
select GENERIC_PENDING_IRQ if SMP
select GENERIC_IRQ_SHOW

8
arch/ia64/include/asm/io.h
View File

@ -96,14 +96,6 @@ extern u64 kern_mem_attribute (unsigned long phys_addr, unsigned long size);
extern int valid_phys_addr_range (phys_addr_t addr, size_t count); /* efi.c */
extern int valid_mmap_phys_addr_range (unsigned long pfn, size_t count);
/*
* The following two macros are deprecated and scheduled for removal.
* Please use the PCI-DMA interface defined in <asm/pci.h> instead.
*/
#define bus_to_virt phys_to_virt
#define virt_to_bus virt_to_phys
#define page_to_bus page_to_phys
# endif /* KERNEL */
/*

1
arch/m68k/Kconfig
View File

@ -30,7 +30,6 @@ config M68K
select OLD_SIGACTION
select OLD_SIGSUSPEND3
select UACCESS_MEMCPY if !MMU
select VIRT_TO_BUS
select ZONE_DMA
config CPU_BIG_ENDIAN

4
arch/m68k/include/asm/virtconvert.h
View File

@ -33,9 +33,11 @@ static inline void *phys_to_virt(unsigned long address)
/*
* IO bus memory addresses are 1:1 with the physical address,
* deprecated globally but still used on two machines.
*/
#if defined(CONFIG_AMIGA) || defined(CONFIG_VME)
#define virt_to_bus virt_to_phys
#define bus_to_virt phys_to_virt
#endif
#endif
#endif

1
arch/microblaze/Kconfig
View File

@ -38,7 +38,6 @@ config MICROBLAZE
select OF_EARLY_FLATTREE
select PCI_DOMAINS_GENERIC if PCI
select PCI_SYSCALL if PCI
select VIRT_TO_BUS
select CPU_NO_EFFICIENT_FFS
select MMU_GATHER_NO_RANGE
select SPARSE_IRQ

2
arch/microblaze/include/asm/io.h
View File

@ -30,8 +30,6 @@ extern resource_size_t isa_mem_base;
#define PCI_IOBASE ((void __iomem *)_IO_BASE)
#define IO_SPACE_LIMIT (0xFFFFFFFF)
#define page_to_bus(page) (page_to_phys(page))
extern void iounmap(volatile void __iomem *addr);
extern void __iomem *ioremap(phys_addr_t address, unsigned long size);

1
arch/mips/Kconfig
View File

@ -100,7 +100,6 @@ config MIPS
select RTC_LIB
select SYSCTL_EXCEPTION_TRACE
select TRACE_IRQFLAGS_SUPPORT
select VIRT_TO_BUS
select ARCH_HAS_ELFCORE_COMPAT
select HAVE_ARCH_KCSAN if 64BIT

9
arch/mips/include/asm/io.h
View File

@ -147,15 +147,6 @@ static inline void *isa_bus_to_virt(unsigned long address)
return phys_to_virt(address);
}
/*
* However PCI ones are not necessarily 1:1 and therefore these interfaces
* are forbidden in portable PCI drivers.
*
* Allow them for x86 for legacy drivers, though.
*/
#define virt_to_bus virt_to_phys
#define bus_to_virt phys_to_virt
/*
* Change "struct page" to physical address.
*/

1
arch/parisc/Kconfig
View File

@ -43,7 +43,6 @@ config PARISC
select SYSCTL_ARCH_UNALIGN_ALLOW
select SYSCTL_EXCEPTION_TRACE
select HAVE_MOD_ARCH_SPECIFIC
select VIRT_TO_BUS
select MODULES_USE_ELF_RELA
select CLONE_BACKWARDS
select TTY # Needed for pdc_cons.c

4
arch/parisc/include/asm/floppy.h
View File

@ -179,7 +179,7 @@ static void _fd_chose_dma_mode(char *addr, unsigned long size)
{
if(can_use_virtual_dma == 2) {
if((unsigned int) addr >= (unsigned int) high_memory ||
virt_to_bus(addr) >= 0x1000000 ||
virt_to_phys(addr) >= 0x1000000 ||
_CROSS_64KB(addr, size, 0))
use_virtual_dma = 1;
else
@ -215,7 +215,7 @@ static int hard_dma_setup(char *addr, unsigned long size, int mode, int io)
doing_pdma = 0;
clear_dma_ff(FLOPPY_DMA);
set_dma_mode(FLOPPY_DMA,mode);
set_dma_addr(FLOPPY_DMA,virt_to_bus(addr));
set_dma_addr(FLOPPY_DMA,virt_to_phys(addr));
set_dma_count(FLOPPY_DMA,size);
enable_dma(FLOPPY_DMA);
return 0;

2
arch/parisc/include/asm/io.h
View File

@ -7,8 +7,6 @@
#define virt_to_phys(a) ((unsigned long)__pa(a))
#define phys_to_virt(a) __va(a)
#define virt_to_bus virt_to_phys
#define bus_to_virt phys_to_virt
static inline unsigned long isa_bus_to_virt(unsigned long addr) {
BUG();

1
arch/powerpc/Kconfig
View File

@ -276,7 +276,6 @@ config PPC
select SYSCTL_EXCEPTION_TRACE
select THREAD_INFO_IN_TASK
select TRACE_IRQFLAGS_SUPPORT
select VIRT_TO_BUS if !PPC64
#
# Please keep this list sorted alphabetically.
#

2
arch/powerpc/include/asm/io.h
View File

@ -985,8 +985,6 @@ static inline void * bus_to_virt(unsigned long address)
}
#define bus_to_virt bus_to_virt
#define page_to_bus(page) (page_to_phys(page) + PCI_DRAM_OFFSET)
#endif /* CONFIG_PPC32 */
/* access ports */

1
arch/riscv/include/asm/page.h
View File

@ -167,7 +167,6 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
#define page_to_virt(page) (pfn_to_virt(page_to_pfn(page)))
#define page_to_phys(page) (pfn_to_phys(page_to_pfn(page)))
#define page_to_bus(page) (page_to_phys(page))
#define phys_to_page(paddr) (pfn_to_page(phys_to_pfn(paddr)))
#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))

1
arch/x86/Kconfig
View File

@ -278,7 +278,6 @@ config X86
select THREAD_INFO_IN_TASK
select TRACE_IRQFLAGS_SUPPORT
select USER_STACKTRACE_SUPPORT
select VIRT_TO_BUS
select HAVE_ARCH_KCSAN if X86_64
select X86_FEATURE_NAMES if PROC_FS
select PROC_PID_ARCH_STATUS if PROC_FS

9
arch/x86/include/asm/io.h
View File

@ -169,15 +169,6 @@ static inline unsigned int isa_virt_to_bus(volatile void *address)
}
#define isa_bus_to_virt phys_to_virt
/*
* However PCI ones are not necessarily 1:1 and therefore these interfaces
* are forbidden in portable PCI drivers.
*
* Allow them on x86 for legacy drivers, though.
*/
#define virt_to_bus virt_to_phys
#define bus_to_virt phys_to_virt
/*
* The default ioremap() behavior is non-cached; if you need something
* else, you probably want one of the following.

1
arch/xtensa/Kconfig
View File

@ -50,7 +50,6 @@ config XTENSA
select MODULES_USE_ELF_RELA
select PERF_USE_VMALLOC
select TRACE_IRQFLAGS_SUPPORT
select VIRT_TO_BUS
help
Xtensa processors are 32-bit RISC machines designed by Tensilica
primarily for embedded systems. These processors are both

3
arch/xtensa/include/asm/io.h
View File

@ -63,9 +63,6 @@ static inline void iounmap(volatile void __iomem *addr)
xtensa_iounmap(addr);
}
#define virt_to_bus virt_to_phys
#define bus_to_virt phys_to_virt
#endif /* CONFIG_MMU */
#include <asm-generic/io.h>

14
include/asm-generic/io.h
View File

@ -1142,20 +1142,6 @@ static inline void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
}
#endif
#ifdef CONFIG_VIRT_TO_BUS
#ifndef virt_to_bus
static inline unsigned long virt_to_bus(void *address)
{
return (unsigned long)address;
}
static inline void *bus_to_virt(unsigned long address)
{
return (void *)address;
}
#endif
#endif
#ifndef memset_io
#define memset_io memset_io
/**

8
mm/Kconfig
View File

@ -639,14 +639,6 @@ config BOUNCE
memory available to the CPU. Enabled by default when HIGHMEM is
selected, but you may say n to override this.
config VIRT_TO_BUS
bool
help
An architecture should select this if it implements the
deprecated interface virt_to_bus(). All new architectures
should probably not select this.
config MMU_NOTIFIER
bool
select SRCU