1 files changed, 35 insertions, 0 deletions

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 <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.