From 79f64dbf68c8a9779a7e9a25e0a9f0217a25b57a Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Wed, 28 Jul 2010 22:01:55 +0100 Subject: 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 Signed-off-by: Russell King --- arch/arm/include/asm/io.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch') diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h index 9db072df2b3..3c91e7c80c2 100644 --- a/arch/arm/include/asm/io.h +++ b/arch/arm/include/asm/io.h @@ -26,6 +26,7 @@ #include #include #include +#include /* * 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) -- cgit v1.2.3