linux-kernel - [PATCH v4 2/4] ARM: Add atomic_io

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Date:	Sat, 24 Aug 2013 12:35:30 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Cc:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Lior Amsalem <alior@...vell.com>,
	Baruch Siach <baruch@...s.co.il>,
	Will Deacon <will.deacon@....com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Subject: [PATCH v4 2/4] ARM: Add atomic_io_modify optimized routines

Implement arch-specific atomic_io_modify and atomic_io_modify_relaxed,
which are based on writel/readl_relaxed and writel_relaxed/readl_relaxed,
respectively.
In both cases, by relaxing the readl, perfomance can be improved.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
---
 arch/arm/include/asm/io.h |  4 ++++
 arch/arm/kernel/io.c      | 29 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index d070741..53637b6 100644
--- a/arch/arm/include/asm/io.h
+++ b/arch/arm/include/asm/io.h
@@ -397,5 +397,9 @@ extern int devmem_is_allowed(unsigned long pfn);
 extern void register_isa_ports(unsigned int mmio, unsigned int io,
 			       unsigned int io_shift);
 
+#define __HAVE_ARCH_ATOMIC_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);
+
 #endif	/* __KERNEL__ */
 #endif	/* __ASM_ARM_IO_H */
diff --git a/arch/arm/kernel/io.c b/arch/arm/kernel/io.c
index dcd5b4d..a8c9c9b 100644
--- a/arch/arm/kernel/io.c
+++ b/arch/arm/kernel/io.c
@@ -1,6 +1,35 @@
 #include <linux/export.h>
 #include <linux/types.h>
 #include <linux/io.h>
+#include <linux/spinlock.h>
+
+static DEFINE_RAW_SPINLOCK(__io_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.
-- 
1.8.1.5

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