arch/mips/lib/delay.c

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

File Facts

System
Linux kernel
Corpus path
arch/mips/lib/delay.c
Extension
.c
Size
1714 bytes
Lines
69
Domain
Architecture Layer
Bucket
arch/mips
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration 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

#include <linux/delay.h>
#include <linux/export.h>
#include <linux/param.h>
#include <linux/smp.h>
#include <linux/stringify.h>

#include <asm/asm.h>
#include <asm/compiler.h>

#ifndef CONFIG_CPU_DADDI_WORKAROUNDS
#define GCC_DADDI_IMM_ASM() "I"
#else
#define GCC_DADDI_IMM_ASM() "r"
#endif

#ifndef CONFIG_HAVE_PLAT_DELAY

void __delay(unsigned long loops)
{
	__asm__ __volatile__ (
	"	.set	noreorder				\n"
	"	.align	3					\n"
	"1:	bnez	%0, 1b					\n"
	"	 " __stringify(LONG_SUBU) "	%0, %1		\n"
	"	.set	reorder					\n"
	: "=r" (loops)
	: GCC_DADDI_IMM_ASM() (1), "0" (loops));
}
EXPORT_SYMBOL(__delay);

/*
 * Division by multiplication: you don't have to worry about
 * loss of precision.
 *
 * Use only for very small delays ( < 1 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)
 */

void __udelay(unsigned long us)
{
	unsigned int lpj = raw_current_cpu_data.udelay_val;

	__delay((us * 0x000010c7ull * HZ * lpj) >> 32);
}
EXPORT_SYMBOL(__udelay);

void __ndelay(unsigned long ns)
{
	unsigned int lpj = raw_current_cpu_data.udelay_val;

	__delay((ns * 0x00000005ull * HZ * lpj) >> 32);
}
EXPORT_SYMBOL(__ndelay);

#endif

Annotation

Implementation Notes