mirror of
https://gitee.com/bianbu-linux/linux-6.6
synced 2025-04-24 14:07:52 -04:00
a9ff696160
Making virt_to_pfn() a static inline taking a strongly typed (const void *) makes the contract of a passing a pointer of that type to the function explicit and exposes any misuse of the macro virt_to_pfn() acting polymorphic and accepting many types such as (void *), (unitptr_t) or (unsigned long) as arguments without warnings. Doing this is a bit intrusive: virt_to_pfn() requires PHYS_PFN_OFFSET and PAGE_SHIFT to be defined, and this is defined in <asm/page.h>, so this must be included *before* <asm/memory.h>. The use of macros were obscuring the unclear inclusion order here, as the macros would eventually be resolved, but a static inline like this cannot be compiled with unresolved macros. The naive solution to include <asm/page.h> at the top of <asm/memory.h> does not work, because <asm/memory.h> sometimes includes <asm/page.h> at the end of itself, which would create a confusing inclusion loop. So instead, take the approach to always unconditionally include <asm/page.h> at the end of <asm/memory.h> arch/arm uses <asm/memory.h> explicitly in a lot of places, however it turns out that if we just unconditionally include <asm/memory.h> into <asm/page.h> and switch all inclusions of <asm/memory.h> to <asm/page.h> instead, we enforce the right order and <asm/memory.h> will always have access to the definitions. Put an inclusion guard in place making it impossible to include <asm/memory.h> explicitly. Link: https://lore.kernel.org/linux-mm/20220701160004.2ffff4e5ab59a55499f4c736@linux-foundation.org/ Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
100 lines
2.8 KiB
C
100 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* Copyright (C) 1995-2004 Russell King
|
|
*
|
|
* Delay routines, using a pre-computed "loops_per_second" value.
|
|
*/
|
|
#ifndef __ASM_ARM_DELAY_H
|
|
#define __ASM_ARM_DELAY_H
|
|
|
|
#include <asm/page.h>
|
|
#include <asm/param.h> /* HZ */
|
|
|
|
/*
|
|
* Loop (or tick) based delay:
|
|
*
|
|
* loops = loops_per_jiffy * jiffies_per_sec * delay_us / us_per_sec
|
|
*
|
|
* where:
|
|
*
|
|
* jiffies_per_sec = HZ
|
|
* us_per_sec = 1000000
|
|
*
|
|
* Therefore the constant part is HZ / 1000000 which is a small
|
|
* fractional number. To make this usable with integer math, we
|
|
* scale up this constant by 2^31, perform the actual multiplication,
|
|
* and scale the result back down by 2^31 with a simple shift:
|
|
*
|
|
* loops = (loops_per_jiffy * delay_us * UDELAY_MULT) >> 31
|
|
*
|
|
* where:
|
|
*
|
|
* UDELAY_MULT = 2^31 * HZ / 1000000
|
|
* = (2^31 / 1000000) * HZ
|
|
* = 2147.483648 * HZ
|
|
* = 2147 * HZ + 483648 * HZ / 1000000
|
|
*
|
|
* 31 is the biggest scale shift value that won't overflow 32 bits for
|
|
* delay_us * UDELAY_MULT assuming HZ <= 1000 and delay_us <= 2000.
|
|
*/
|
|
#define MAX_UDELAY_MS 2
|
|
#define UDELAY_MULT UL(2147 * HZ + 483648 * HZ / 1000000)
|
|
#define UDELAY_SHIFT 31
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
struct delay_timer {
|
|
unsigned long (*read_current_timer)(void);
|
|
unsigned long freq;
|
|
};
|
|
|
|
extern struct arm_delay_ops {
|
|
void (*delay)(unsigned long);
|
|
void (*const_udelay)(unsigned long);
|
|
void (*udelay)(unsigned long);
|
|
unsigned long ticks_per_jiffy;
|
|
} arm_delay_ops;
|
|
|
|
#define __delay(n) arm_delay_ops.delay(n)
|
|
|
|
/*
|
|
* This function intentionally does not exist; if you see references to
|
|
* it, it means that you're calling udelay() with an out of range value.
|
|
*
|
|
* With currently imposed limits, this means that we support a max delay
|
|
* of 2000us. Further limits: HZ<=1000
|
|
*/
|
|
extern void __bad_udelay(void);
|
|
|
|
/*
|
|
* division by multiplication: you don't have to worry about
|
|
* loss of precision.
|
|
*
|
|
* Use only for very small delays ( < 2 msec). Should probably use a
|
|
* lookup table, really, as the multiplications take much too long with
|
|
* short delays. This is a "reasonable" implementation, though (and the
|
|
* first constant multiplications gets optimized away if the delay is
|
|
* a constant)
|
|
*/
|
|
#define __udelay(n) arm_delay_ops.udelay(n)
|
|
#define __const_udelay(n) arm_delay_ops.const_udelay(n)
|
|
|
|
#define udelay(n) \
|
|
(__builtin_constant_p(n) ? \
|
|
((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
|
|
__const_udelay((n) * UDELAY_MULT)) : \
|
|
__udelay(n))
|
|
|
|
/* Loop-based definitions for assembly code. */
|
|
extern void __loop_delay(unsigned long loops);
|
|
extern void __loop_udelay(unsigned long usecs);
|
|
extern void __loop_const_udelay(unsigned long);
|
|
|
|
/* Delay-loop timer registration. */
|
|
#define ARCH_HAS_READ_CURRENT_TIMER
|
|
extern void register_current_timer_delay(const struct delay_timer *timer);
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
|
|
#endif /* defined(_ARM_DELAY_H) */
|
|
|