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ARM: 6273/1: Add barriers to the I/O accessors if ARM_DMA_MEM_BUFFERABLE 

When the coherent DMA buffers are mapped as Normal Non-cacheable
(ARM_DMA_MEM_BUFFERABLE enabled), buffer accesses are no longer ordered
with Device memory accesses causing failures in device drivers that do
not use the mandatory memory barriers before starting a DMA transfer.
LKML discussions led to the conclusion that such barriers have to be
added to the I/O accessors:

http://thread.gmane.org/gmane.linux.kernel/683509/focus=686153
http://thread.gmane.org/gmane.linux.ide/46414
http://thread.gmane.org/gmane.linux.kernel.cross-arch/5250

This patch introduces a wmb() barrier to the write*() I/O accessors to
handle the situations where Normal Non-cacheable writes are still in the
processor (or L2 cache controller) write buffer before a DMA transfer
command is issued. For the read*() accessors, a rmb() is introduced
after the I/O to avoid speculative loads where the driver polls for a
DMA transfer ready bit.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Catalin Marinas 2010-07-28 22:01:55 +01:00 committed by Russell King
parent 6775a558fe
commit 79f64dbf68
1 changed files with 11 additions and 0 deletions
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11
arch/arm/include/asm/io.h
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@ -26,6 +26,7 @@
#include <linux/types.h>
#include <asm/byteorder.h>
#include <asm/memory.h>
#include <asm/system.h>
/*
* ISA I/O bus memory addresses are 1:1 with the physical address.
@ -191,6 +192,15 @@ extern void _memset_io(volatile void __iomem *, int, size_t);
#define writel_relaxed(v,c) ((void)__raw_writel((__force u32) \
cpu_to_le32(v),__mem_pci(c)))
#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
#define readb(c) ({ u8 __v = readb_relaxed(c); rmb(); __v; })
#define readw(c) ({ u16 __v = readw_relaxed(c); rmb(); __v; })
#define readl(c) ({ u32 __v = readl_relaxed(c); rmb(); __v; })
#define writeb(v,c) ({ wmb(); writeb_relaxed(v,c); })
#define writew(v,c) ({ wmb(); writew_relaxed(v,c); })
#define writel(v,c) ({ wmb(); writel_relaxed(v,c); })
#else
#define readb(c) readb_relaxed(c)
#define readw(c) readw_relaxed(c)
#define readl(c) readl_relaxed(c)
@ -198,6 +208,7 @@ extern void _memset_io(volatile void __iomem *, int, size_t);
#define writeb(v,c) writeb_relaxed(v,c)
#define writew(v,c) writew_relaxed(v,c)
#define writel(v,c) writel_relaxed(v,c)
#endif
#define readsb(p,d,l) __raw_readsb(__mem_pci(p),d,l)
#define readsw(p,d,l) __raw_readsw(__mem_pci(p),d,l)