path: root/arch/arm
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authorAlexander Holler <holler@ahsoftware.de>2011-01-09 12:19:44 +0000
committerAlbert Aribaud <albert.aribaud@free.fr>2011-02-02 00:54:44 +0100
commit3c0659b535b075be124c3d2a0714e55e65c46737 (patch)
treee8d99c2dff1e0d6afdaf83b6b5301dbe47ce7e5b /arch/arm
parent3c152165c78408e44845f2d08469db887f050e43 (diff)
ARM: Avoid compiler optimization for readb, writeb and friends.
gcc 4.5.1 seems to ignore (at least some) volatile definitions, avoid that as done in the kernel. Reading C99 6.7.3 8 and the comment 114) there, I think it is a bug of that gcc version to ignore the volatile type qualifier used e.g. in __arch_getl(). Anyway, using a definition as in the kernel headers avoids such optimizations when gcc 4.5.1 is used. Maybe the headers as used in the current linux-kernel should be used, but to avoid large changes, I've just added a small change to the current headers. Signed-off-by: Alexander Holler <holler@ahsoftware.de> Signed-off-by: Dirk Behme <dirk.behme@googlemail.com> Signed-off-by: Wolfgang Denk <wd@denx.de> Cc: Alessandro Rubini <rubini-list@gnudd.com> Tested-by: Thomas Weber <weber@corscience.de> Acked-by: Alexander Holler <holler@ahsoftware.de> Tested-by: Alexander Holler <holler@ahsoftware.de>
Diffstat (limited to 'arch/arm')
1 files changed, 20 insertions, 12 deletions
diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index ff1518eb0..3886f1589 100644
--- a/arch/arm/include/asm/io.h
+++ b/arch/arm/include/asm/io.h
@@ -117,21 +117,29 @@ extern inline void __raw_readsl(unsigned int addr, void *data, int longlen)
*buf++ = __arch_getl(addr);
-#define __raw_writeb(v,a) __arch_putb(v,a)
-#define __raw_writew(v,a) __arch_putw(v,a)
-#define __raw_writel(v,a) __arch_putl(v,a)
+#define __raw_writeb(v,a) __arch_putb(v,a)
+#define __raw_writew(v,a) __arch_putw(v,a)
+#define __raw_writel(v,a) __arch_putl(v,a)
-#define __raw_readb(a) __arch_getb(a)
-#define __raw_readw(a) __arch_getw(a)
-#define __raw_readl(a) __arch_getl(a)
+#define __raw_readb(a) __arch_getb(a)
+#define __raw_readw(a) __arch_getw(a)
+#define __raw_readl(a) __arch_getl(a)
-#define writeb(v,a) __arch_putb(v,a)
-#define writew(v,a) __arch_putw(v,a)
-#define writel(v,a) __arch_putl(v,a)
+ * TODO: The kernel offers some more advanced versions of barriers, it might
+ * have some advantages to use them instead of the simple one here.
+ */
+#define dmb() __asm__ __volatile__ ("" : : : "memory")
+#define __iormb() dmb()
+#define __iowmb() dmb()
+#define writeb(v,c) ({ __iowmb(); __arch_putb(v,c); v; })
+#define writew(v,c) ({ __iowmb(); __arch_putw(v,c); v; })
+#define writel(v,c) ({ __iowmb(); __arch_putl(v,c); v; })
-#define readb(a) __arch_getb(a)
-#define readw(a) __arch_getw(a)
-#define readl(a) __arch_getl(a)
+#define readb(c) ({ u8 __v = __arch_getb(c); __iormb(); __v; })
+#define readw(c) ({ u16 __v = __arch_getw(c); __iormb(); __v; })
+#define readl(c) ({ u32 __v = __arch_getl(c); __iormb(); __v; })
* The compiler seems to be incapable of optimising constants