mirror of
https://github.com/torvalds/linux.git
synced 2024-11-28 15:11:31 +00:00
a87e553fab
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>
45 lines
1.1 KiB
C
45 lines
1.1 KiB
C
#ifndef __ASM_GENERIC_DELAY_H
|
|
#define __ASM_GENERIC_DELAY_H
|
|
|
|
/* Undefined functions to get compile-time errors */
|
|
extern void __bad_udelay(void);
|
|
extern void __bad_ndelay(void);
|
|
|
|
extern void __udelay(unsigned long usecs);
|
|
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) \
|
|
({ \
|
|
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) \
|
|
({ \
|
|
if (__builtin_constant_p(n)) { \
|
|
if ((n) / 20000 >= 1) \
|
|
__bad_ndelay(); \
|
|
else \
|
|
__const_udelay((n) * 5ul); \
|
|
} else { \
|
|
__ndelay(n); \
|
|
} \
|
|
})
|
|
|
|
#endif /* __ASM_GENERIC_DELAY_H */
|