Dear Alexander Holler,
In message <1292711230-3234-1-git-send-email-hol...@ahsoftware.de> you wrote:
> gcc 4.5.1 seems to ignore (at least some) volatile definitions,
> avoid that as done in the kernel.
...
> +#define writeb(v,c) ({ __iowmb(); __arch_putb(v,c); })
> +#define writew(v,c) ({ __iowmb(); __arch_putw(v,c); })
> +#define writel(v,c) ({ __iowmb(); __arch_putl(v,c); })
http://www.codesourcery.com/archives/arm-gnu/msg03990.html explains
why this construct is causing errors in cases where an additional read
from the address is unsupported.
Can you please try the following patch instead?
-------------------------------------------------------------------------
>From 4672bbddaf8ce7e17a99ba737782cc527d46e5eb Mon Sep 17 00:00:00 2001
From: Alexander Holler <hol...@ahsoftware.de>
Date: Sat, 18 Dec 2010 23:27:10 +0100
Subject: [PATCH] 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 <hol...@ahsoftware.de>
Signed-off-by: Wolfgang Denk <w...@denx.de>
---
arch/arm/include/asm/io.h | 32 ++++++++++++++++++++------------
1 files changed, 20 insertions(+), 12 deletions(-)
diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index ff1518e..647503a 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) do { __iowmb(); __arch_putb(v,c); } while (0)
+#define writew(v,c) do { __iowmb(); __arch_putw(v,c); } while (0)
+#define writel(v,c) do { __iowmb(); __arch_putl(v,c); } while (0)
-#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
--
1.7.3.3
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de
Where there's no emotion, there's no motive for violence.
-- Spock, "Dagger of the Mind", stardate 2715.1
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