第六章——uboot for tiny4412中MMU虚拟地址设置

最新推荐文章于 2021-11-01 23:03:30 发布

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本文介绍了一种针对SMDKC210平台的内存管理单元(MMU)配置方法，包括MMU的启用步骤及MMU表的具体设置。通过对MMU表的详细划分，确保了不同内存区域的正确映射。

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enable_mmu:
	/* enable domain access */
	ldr	r5, =0x0000ffff
	mcr	p15, 0, r5, c3, c0, 0		@load domain access register

	/* Set the TTB register */
	ldr	r0, =mmu_table
	ldr	r1, =CONFIG_PHY_UBOOT_BASE
	ldr	r2, =0xfff00000
	bic	r0, r0, r2
	orr	r1, r0, r1
	mcr	p15, 0, r1, c2, c0, 0

	/* Enable the MMU */
mmu_on:
	mrc	p15, 0, r0, c1, c0, 0
	orr	r0, r0, #1
	mcr	p15, 0, r0, c1, c0, 0
	nop
	nop
	nop
	nop
	mov	pc, lr

/*
 * MMU Table for SMDKC210
 * 0x0000_0000 -- 0x1FFF_FFFF => A:0x0000_0000 -- 0x1FFF_FFFF
 * 0x2000_0000 -- 0x3FFF_FFFF => Not Allowed
 * 0x4000_0000 -- 0x5FFF_FFFF => A:0x4000_0000 -- 0x5FFF_FFFF
 * 0x6000_0000 -- 0xBFFF_FFFF => Not Allowed
 * 0xC000_0000 -- 0xDFFF_FFFF => A:0x4000_0000 -- 0X5FFF_FFFF
 * 0xE000_0000 -- 0xFFFF_FFFF => Not Allowed
 */

	/* form a first-level section entry */
.macro FL_SECTION_ENTRY base,ap,d,c,b
	.word (\base << 20) | (\ap << 10) | \
	      (\d << 5) | (1<<4) | (\c << 3) | (\b << 2) | (1<<1)
.endm

.section .mmudata, "a"
	.align 14

	// the following alignment creates the mmu table at address 0x4000.
	.globl mmu_table
mmu_table:

	.set __base,0
	// Access for iRAM
	.rept 0x200
	FL_SECTION_ENTRY __base,3,0,0,0
	.set __base,__base+1
	.endr

	// Not Allowed
	.rept 0x400 - 0x200
	.word 0x00000000
	.endr

	.set __base,0x400
	// 512MB for SDRAM with cacheable
	.rept 0x800 - 0x400
	FL_SECTION_ENTRY __base,3,0,1,1
	.set __base,__base+1
	.endr

	// access is not allowed.
	.rept 0xc00 - 0x800
	.word 0x00000000
	.endr

	.set __base,0x400
	// 512MB for SDRAM with cacheable
	.rept 0xE00 - 0xC00
	FL_SECTION_ENTRY __base,3,0,1,1
	.set __base,__base+1
	.endr

	// access is not allowed.
	.rept 0x1000 - 0xE00
	.word 0x00000000
	.endr