forked from mirrors/linux
4d17c25eaf
A recent rework on delay functions wrongly ended up calling __udelay()
instead of __ndelay() for nanosecond delays, increasing those by 1000.
As a result hangs have been observed on boot
Restore the right function calls.
Fixes: 19e2d91d8c ("delay: Rework udelay and ndelay")
Reported-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/all/20241121152931.51884-1-frederic@kernel.org
87 lines
2.8 KiB
C
87 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_GENERIC_DELAY_H
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#define __ASM_GENERIC_DELAY_H
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#include <linux/math.h>
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#include <vdso/time64.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 microseconds/nanosecond delay multiplicators are used to convert a
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* constant microseconds/nanoseconds value to a value which can be used by the
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* architectures specific implementation to transform it into loops.
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*/
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#define UDELAY_CONST_MULT ((unsigned long)DIV_ROUND_UP(1ULL << 32, USEC_PER_SEC))
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#define NDELAY_CONST_MULT ((unsigned long)DIV_ROUND_UP(1ULL << 32, NSEC_PER_SEC))
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/*
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* The maximum constant udelay/ndelay value picked out of thin air to prevent
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* too long constant udelays/ndelays.
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*/
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#define DELAY_CONST_MAX 20000
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/**
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* udelay - Inserting a delay based on microseconds with busy waiting
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* @usec: requested delay in microseconds
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*
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* When delaying in an atomic context ndelay(), udelay() and mdelay() are the
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* only valid variants of delaying/sleeping to go with.
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*
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* When inserting delays in non atomic context which are shorter than the time
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* which is required to queue e.g. an hrtimer and to enter then the scheduler,
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* it is also valuable to use udelay(). But it is not simple to specify a
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* generic threshold for this which will fit for all systems. An approximation
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* is a threshold for all delays up to 10 microseconds.
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*
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* When having a delay which is larger than the architecture specific
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* %MAX_UDELAY_MS value, please make sure mdelay() is used. Otherwise a overflow
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* risk is given.
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*
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* Please note that ndelay(), udelay() and mdelay() may return early for several
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* reasons (https://lists.openwall.net/linux-kernel/2011/01/09/56):
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*
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* #. computed loops_per_jiffy too low (due to the time taken to execute the
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* timer interrupt.)
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* #. cache behaviour affecting the time it takes to execute the loop function.
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* #. CPU clock rate changes.
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*/
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static __always_inline void udelay(unsigned long usec)
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{
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if (__builtin_constant_p(usec)) {
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if (usec >= DELAY_CONST_MAX)
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__bad_udelay();
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else
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__const_udelay(usec * UDELAY_CONST_MULT);
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} else {
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__udelay(usec);
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}
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}
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/**
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* ndelay - Inserting a delay based on nanoseconds with busy waiting
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* @nsec: requested delay in nanoseconds
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*
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* See udelay() for basic information about ndelay() and it's variants.
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*/
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static __always_inline void ndelay(unsigned long nsec)
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{
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if (__builtin_constant_p(nsec)) {
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if (nsec >= DELAY_CONST_MAX)
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__bad_ndelay();
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else
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__const_udelay(nsec * NDELAY_CONST_MULT);
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} else {
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__ndelay(nsec);
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}
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}
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#define ndelay(x) ndelay(x)
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#endif /* __ASM_GENERIC_DELAY_H */
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