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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
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#define __ASM_GENERIC_DELAY_H
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/* Undefined functions to get compile-time errors */
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extern void __bad_udelay(void);
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extern void __bad_ndelay(void);
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extern void __udelay(unsigned long usecs);
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extern void __ndelay(unsigned long nsecs);
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extern void __const_udelay(unsigned long xloops);
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extern void __delay(unsigned long loops);
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/*
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* The weird n/20000 thing suppresses a "comparison is always false due to
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* limited range of data type" warning with non-const 8-bit arguments.
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*/
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/* 0x10c7 is 2**32 / 1000000 (rounded up) */
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#define udelay(n) \
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({ \
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if (__builtin_constant_p(n)) { \
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if ((n) / 20000 >= 1) \
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__bad_udelay(); \
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else \
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__const_udelay((n) * 0x10c7ul); \
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} else { \
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__udelay(n); \
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} \
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})
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/* 0x5 is 2**32 / 1000000000 (rounded up) */
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#define ndelay(n) \
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({ \
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if (__builtin_constant_p(n)) { \
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if ((n) / 20000 >= 1) \
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__bad_ndelay(); \
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else \
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__const_udelay((n) * 5ul); \
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} else { \
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__ndelay(n); \
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} \
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})
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#endif /* __ASM_GENERIC_DELAY_H */
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