diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2010-07-28 22:01:55 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2010-07-29 14:04:37 +0100 |
| commit | 79f64dbf68c8a9779a7e9a25e0a9f0217a25b57a (patch) | |
| tree | bd75d76d566c5dd211d310bf136cf3e4b07184ae | |
| parent | 6775a558fece413376e1dacd435adb5fbe225f40 (diff) | |
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>
| -rw-r--r-- | arch/arm/include/asm/io.h | 11 |
1 files changed, 11 insertions, 0 deletions
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 <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) |