arch/arm/mach-omap1/sram.S

Source file repositories/reference/linux-study-clean/arch/arm/mach-omap1/sram.S

File Facts

System
Linux kernel
Corpus path
arch/arm/mach-omap1/sram.S
Extension
.S
Size
1437 bytes
Lines
59
Domain
Architecture Layer
Bucket
arch/arm
Inferred role
Architecture Layer: arch/arm
Status
atlas-only

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/linkage.h>
#include <linux/soc/ti/omap1-io.h>

#include <asm/assembler.h>

#include "hardware.h"
#include "iomap.h"

	.text

/*
 * Reprograms ULPD and CKCTL.
 */
	.align	3
ENTRY(omap1_sram_reprogram_clock)
	stmfd	sp!, {r0 - r12, lr}		@ save registers on stack

	mov	r2, #OMAP1_IO_ADDRESS(DPLL_CTL) & 0xff000000
	orr	r2, r2, #OMAP1_IO_ADDRESS(DPLL_CTL) & 0x00ff0000
	orr	r2, r2, #OMAP1_IO_ADDRESS(DPLL_CTL) & 0x0000ff00

	mov	r3, #OMAP1_IO_ADDRESS(ARM_CKCTL) & 0xff000000
	orr	r3, r3, #OMAP1_IO_ADDRESS(ARM_CKCTL) & 0x00ff0000
	orr	r3, r3, #OMAP1_IO_ADDRESS(ARM_CKCTL) & 0x0000ff00

	tst	r0, #1 << 4			@ want lock mode?
	beq	newck				@ nope
	bic	r0, r0, #1 << 4			@ else clear lock bit
	strh	r0, [r2]			@ set dpll into bypass mode
	orr	r0, r0, #1 << 4			@ set lock bit again

newck:
	strh	r1, [r3]			@ write new ckctl value
	strh	r0, [r2]			@ write new dpll value

	mov	r4, #0x0700			@ let the clocks settle
	orr	r4, r4, #0x00ff
delay:	sub	r4, r4, #1
	cmp	r4, #0
	bne	delay

lock:	ldrh	r4, [r2], #0			@ read back dpll value
	tst	r0, #1 << 4			@ want lock mode?
	beq	out				@ nope
	tst	r4, #1 << 0			@ dpll rate locked?
	beq	lock				@ try again

out:
	ldmfd	sp!, {r0 - r12, pc}		@ restore regs and return
ENTRY(omap1_sram_reprogram_clock_sz)
	.word	. - omap1_sram_reprogram_clock

Annotation

Implementation Notes