From c5ca95b507c8a2a69e49eeda539b41bd76922d7f Mon Sep 17 00:00:00 2001 From: Ezequiel Garcia Date: Wed, 18 Dec 2013 23:08:52 +0100 Subject: 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 Acked-by: Jason Cooper Acked-by: Catalin Marinas Signed-off-by: Ezequiel Garcia Signed-off-by: Russell King --- arch/arm/include/asm/io.h | 6 ++++++ arch/arm/kernel/io.c | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h index fbeb39c869e9..8aa4cca74501 100644 --- a/arch/arm/include/asm/io.h +++ b/arch/arm/include/asm/io.h @@ -37,6 +37,12 @@ #define isa_page_to_bus page_to_phys #define isa_bus_to_virt phys_to_virt +/* + * Atomic MMIO-wide IO modify + */ +extern void atomic_io_modify(void __iomem *reg, u32 mask, u32 set); +extern void atomic_io_modify_relaxed(void __iomem *reg, u32 mask, u32 set); + /* * Generic IO read/write. These perform native-endian accesses. Note * that some architectures will want to re-define __raw_{read,write}w. diff --git a/arch/arm/kernel/io.c b/arch/arm/kernel/io.c index dcd5b4d86143..9203cf883330 100644 --- a/arch/arm/kernel/io.c +++ b/arch/arm/kernel/io.c @@ -1,6 +1,41 @@ #include #include #include +#include + +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. -- cgit v1.2.3