arch/sh/lib/delay.c

Source file repositories/reference/linux-study-clean/arch/sh/lib/delay.c

File Facts

System
Linux kernel
Corpus path
arch/sh/lib/delay.c
Extension
.c
Size
1103 bytes
Lines
55
Domain
Architecture Layer
Bucket
arch/sh
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 *	Precise Delay Loops for SuperH
 *
 *	Copyright (C) 1999 Niibe Yutaka & Kaz Kojima
 */

#include <linux/sched.h>
#include <linux/delay.h>

void __delay(unsigned long loops)
{
	__asm__ __volatile__(
		/*
		 * ST40-300 appears to have an issue with this code,
		 * normally taking two cycles each loop, as with all
		 * other SH variants. If however the branch and the
		 * delay slot straddle an 8 byte boundary, this increases
		 * to 3 cycles.
		 * This align directive ensures this doesn't occur.
		 */
		".balign 8\n\t"

		"tst	%0, %0\n\t"
		"1:\t"
		"bf/s	1b\n\t"
		" dt	%0"
		: "=r" (loops)
		: "0" (loops)
		: "t");
}

inline void __const_udelay(unsigned long xloops)
{
	xloops *= 4;
	__asm__("dmulu.l	%0, %2\n\t"
		"sts	mach, %0"
		: "=r" (xloops)
		: "0" (xloops),
		  "r" (cpu_data[raw_smp_processor_id()].loops_per_jiffy * (HZ/4))
		: "macl", "mach");
	__delay(++xloops);
}

void __udelay(unsigned long usecs)
{
	__const_udelay(usecs * 0x000010c6);  /* 2**32 / 1000000 */
}

void __ndelay(unsigned long nsecs)
{
	__const_udelay(nsecs * 0x00000005);
}

Annotation

Implementation Notes