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authorAndrew Morton <akpm@linux-foundation.org>2011-07-18 15:28:20 +0200
committerJonas Bonn <jonas@southpole.se>2011-07-22 18:45:33 +0200
commita87e553fabe8ceadc6f90889066559234cf194c7 (patch)
tree680a59e97378218fd13e0d1400706d84681c921c /include/asm-generic
parent30ab2b034fa87472d700f584e277e3aeb7a84d2c (diff)
asm-generic: delay.h fix udelay and ndelay for 8 bit args
With a non-constant 8-bit argument, a call to udelay() generates a warning: drivers/gpu/drm/radeon/atom.c: In function 'atom_op_delay': drivers/gpu/drm/radeon/atom.c:654: warning: comparison is always false due to limited range of data type The code looks like it works OK with an 8-bit arg, and the calling code is doing nothing wrong, so udelay() needs fixing. Fixing it was rather tricky. Simply typecasting `n' in the comparison with 20000 didn't change anything. Hence the divide-by-20000 trick. Using a do{}while loop didn't work because udelay() is used in ?: statements, hence the ({...}) construct. While I was there I replaced the brain-bending ?:?:?: mess with nice if/else code. Probably other architectures are generating the same warning and can use a similar change. [Taken from the x86 tree and moved to asm-generic by Jonas Bonn] Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jonas Bonn <jonas@southpole.se>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/delay.h33
1 files changed, 27 insertions, 6 deletions
diff --git a/include/asm-generic/delay.h b/include/asm-generic/delay.h
index 6511b99c5f17..0f79054ce7cd 100644
--- a/include/asm-generic/delay.h
+++ b/include/asm-generic/delay.h
@@ -10,14 +10,35 @@ extern void __ndelay(unsigned long nsecs);
extern void __const_udelay(unsigned long xloops);
extern void __delay(unsigned long loops);
+/*
+ * The weird n/20000 thing suppresses a "comparison is always false due to
+ * limited range of data type" warning with non-const 8-bit arguments.
+ */
+
/* 0x10c7 is 2**32 / 1000000 (rounded up) */
-#define udelay(n) (__builtin_constant_p(n) ? \
- ((n) > 20000 ? __bad_udelay() : __const_udelay((n) * 0x10c7ul)) : \
- __udelay(n))
+#define udelay(n) \
+ ({ \
+ if (__builtin_constant_p(n)) { \
+ if ((n) / 20000 >= 1) \
+ __bad_udelay(); \
+ else \
+ __const_udelay((n) * 0x10c7ul); \
+ } else { \
+ __udelay(n); \
+ } \
+ })
/* 0x5 is 2**32 / 1000000000 (rounded up) */
-#define ndelay(n) (__builtin_constant_p(n) ? \
- ((n) > 20000 ? __bad_ndelay() : __const_udelay((n) * 5ul)) : \
- __ndelay(n))
+#define ndelay(n) \
+ ({ \
+ if (__builtin_constant_p(n)) { \
+ if ((n) / 20000 >= 1) \
+ __bad_ndelay(); \
+ else \
+ __const_udelay((n) * 5ul); \
+ } else { \
+ __ndelay(n); \
+ } \
+ })
#endif /* __ASM_GENERIC_DELAY_H */