linux/arch/arm/kernel/io.c
Ezequiel Garcia c5ca95b507 ARM: 7930/1: Introduce atomic MMIO modify
Some SoC have MMIO regions that are shared across orthogonal
subsystems. This commit implements a possible solution for the
thread-safe access of such regions through a spinlock-protected API.

Concurrent access is protected with a single spinlock for the
entire MMIO address space. While this protects shared-registers,
it also serializes access to unrelated/unshared registers.

We add relaxed and non-relaxed variants, by using writel_relaxed and writel,
respectively. The rationale for this is that some users may not require
register write completion but only thread-safe access to a register.

Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2014-01-28 14:06:25 +00:00

86 lines
1.7 KiB
C

#include <linux/export.h>
#include <linux/types.h>
#include <linux/io.h>
#include <linux/spinlock.h>
static DEFINE_RAW_SPINLOCK(__io_lock);
/*
* Generic atomic MMIO modify.
*
* Allows thread-safe access to registers shared by unrelated subsystems.
* The access is protected by a single MMIO-wide lock.
*/
void atomic_io_modify_relaxed(void __iomem *reg, u32 mask, u32 set)
{
unsigned long flags;
u32 value;
raw_spin_lock_irqsave(&__io_lock, flags);
value = readl_relaxed(reg) & ~mask;
value |= (set & mask);
writel_relaxed(value, reg);
raw_spin_unlock_irqrestore(&__io_lock, flags);
}
EXPORT_SYMBOL(atomic_io_modify_relaxed);
void atomic_io_modify(void __iomem *reg, u32 mask, u32 set)
{
unsigned long flags;
u32 value;
raw_spin_lock_irqsave(&__io_lock, flags);
value = readl_relaxed(reg) & ~mask;
value |= (set & mask);
writel(value, reg);
raw_spin_unlock_irqrestore(&__io_lock, flags);
}
EXPORT_SYMBOL(atomic_io_modify);
/*
* Copy data from IO memory space to "real" memory space.
* This needs to be optimized.
*/
void _memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
{
unsigned char *t = to;
while (count) {
count--;
*t = readb(from);
t++;
from++;
}
}
/*
* Copy data from "real" memory space to IO memory space.
* This needs to be optimized.
*/
void _memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
{
const unsigned char *f = from;
while (count) {
count--;
writeb(*f, to);
f++;
to++;
}
}
/*
* "memset" on IO memory space.
* This needs to be optimized.
*/
void _memset_io(volatile void __iomem *dst, int c, size_t count)
{
while (count) {
count--;
writeb(c, dst);
dst++;
}
}
EXPORT_SYMBOL(_memcpy_fromio);
EXPORT_SYMBOL(_memcpy_toio);
EXPORT_SYMBOL(_memset_io);