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| author | Andrew Morton <akpm@linux-foundation.org> | 2011-07-18 15:28:20 +0200 |
|---|---|---|
| committer | Jonas Bonn <jonas@southpole.se> | 2011-07-22 18:45:33 +0200 |
| commit | a87e553fabe8ceadc6f90889066559234cf194c7 (patch) | |
| tree | 680a59e97378218fd13e0d1400706d84681c921c | |
| parent | asm-generic: adapt delay.h to common implementation (diff) | |
| download | linux-a87e553fabe8ceadc6f90889066559234cf194c7.tar.xz linux-a87e553fabe8ceadc6f90889066559234cf194c7.zip | |
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>
| -rw-r--r-- | include/asm-generic/delay.h | 33 |
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 */ |