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https://github.com/torvalds/linux
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c5ca95b507
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>
85 lines
1.7 KiB
C
85 lines
1.7 KiB
C
#include <linux/export.h>
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#include <linux/types.h>
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#include <linux/io.h>
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#include <linux/spinlock.h>
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static DEFINE_RAW_SPINLOCK(__io_lock);
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/*
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* Generic atomic MMIO modify.
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*
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* Allows thread-safe access to registers shared by unrelated subsystems.
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* The access is protected by a single MMIO-wide lock.
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*/
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void atomic_io_modify_relaxed(void __iomem *reg, u32 mask, u32 set)
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{
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unsigned long flags;
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u32 value;
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raw_spin_lock_irqsave(&__io_lock, flags);
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value = readl_relaxed(reg) & ~mask;
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value |= (set & mask);
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writel_relaxed(value, reg);
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raw_spin_unlock_irqrestore(&__io_lock, flags);
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}
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EXPORT_SYMBOL(atomic_io_modify_relaxed);
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void atomic_io_modify(void __iomem *reg, u32 mask, u32 set)
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{
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unsigned long flags;
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u32 value;
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raw_spin_lock_irqsave(&__io_lock, flags);
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value = readl_relaxed(reg) & ~mask;
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value |= (set & mask);
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writel(value, reg);
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raw_spin_unlock_irqrestore(&__io_lock, flags);
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}
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EXPORT_SYMBOL(atomic_io_modify);
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/*
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* Copy data from IO memory space to "real" memory space.
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* This needs to be optimized.
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*/
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void _memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
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{
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unsigned char *t = to;
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while (count) {
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count--;
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*t = readb(from);
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t++;
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from++;
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}
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}
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/*
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* Copy data from "real" memory space to IO memory space.
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* This needs to be optimized.
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*/
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void _memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
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{
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const unsigned char *f = from;
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while (count) {
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count--;
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writeb(*f, to);
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f++;
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to++;
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}
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}
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/*
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* "memset" on IO memory space.
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* This needs to be optimized.
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*/
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void _memset_io(volatile void __iomem *dst, int c, size_t count)
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{
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while (count) {
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count--;
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writeb(c, dst);
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dst++;
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}
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}
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EXPORT_SYMBOL(_memcpy_fromio);
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EXPORT_SYMBOL(_memcpy_toio);
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EXPORT_SYMBOL(_memset_io);
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