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/*
* linux/arch/unicore32/kernel/head.S
*
* Code specific to PKUnity SoC and UniCore ISA
*
* Copyright (C) 2001-2010 GUAN Xue-tao
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <linux/init.h>
#include <asm/assembler.h>
#include <asm/ptrace.h>
#include <generated/asm-offsets.h>
#include <asm/memory.h>
#include <asm/thread_info.h>
#include <asm/system.h>
#include <asm/pgtable-hwdef.h>
#if (PHYS_OFFSET & 0x003fffff)
#error "PHYS_OFFSET must be at an even 4MiB boundary!"
#endif
#define KERNEL_RAM_VADDR (PAGE_OFFSET + KERNEL_IMAGE_START)
#define KERNEL_RAM_PADDR (PHYS_OFFSET + KERNEL_IMAGE_START)
#define KERNEL_PGD_PADDR (KERNEL_RAM_PADDR - 0x1000)
#define KERNEL_PGD_VADDR (KERNEL_RAM_VADDR - 0x1000)
#define KERNEL_START KERNEL_RAM_VADDR
#define KERNEL_END _end
/*
* swapper_pg_dir is the virtual address of the initial page table.
* We place the page tables 4K below KERNEL_RAM_VADDR. Therefore, we must
* make sure that KERNEL_RAM_VADDR is correctly set. Currently, we expect
* the least significant 16 bits to be 0x8000, but we could probably
* relax this restriction to KERNEL_RAM_VADDR >= PAGE_OFFSET + 0x1000.
*/
#if (KERNEL_RAM_VADDR & 0xffff) != 0x8000
#error KERNEL_RAM_VADDR must start at 0xXXXX8000
#endif
.globl swapper_pg_dir
.equ swapper_pg_dir, KERNEL_RAM_VADDR - 0x1000
/*
* Kernel startup entry point.
* ---------------------------
*
* This is normally called from the decompressor code. The requirements
* are: MMU = off, D-cache = off, I-cache = dont care
*
* This code is mostly position independent, so if you link the kernel at
* 0xc0008000, you call this at __pa(0xc0008000).
*/
__HEAD
ENTRY(stext)
@ set asr
mov r0, #PRIV_MODE @ ensure priv mode
or r0, #PSR_R_BIT | PSR_I_BIT @ disable irqs
mov.a asr, r0
@ process identify
movc r0, p0.c0, #0 @ cpuid
movl r1, 0xff00ffff @ mask
movl r2, 0x4d000863 @ value
and r0, r1, r0
cxor.a r0, r2
bne __error_p @ invalid processor id
/*
* Clear the 4K level 1 swapper page table
*/
movl r0, #KERNEL_PGD_PADDR @ page table address
mov r1, #0
add r2, r0, #0x1000
101: stw.w r1, [r0]+, #4
stw.w r1, [r0]+, #4
stw.w r1, [r0]+, #4
stw.w r1, [r0]+, #4
cxor.a r0, r2
bne 101b
movl r4, #KERNEL_PGD_PADDR @ page table address
mov r7, #PMD_TYPE_SECT | PMD_PRESENT @ page size: section
or r7, r7, #PMD_SECT_CACHEABLE @ cacheable
or r7, r7, #PMD_SECT_READ | PMD_SECT_WRITE | PMD_SECT_EXEC
/*
* Create identity mapping for first 4MB of kernel to
* cater for the MMU enable. This identity mapping
* will be removed by paging_init(). We use our current program
* counter to determine corresponding section base address.
*/
mov r6, pc
mov r6, r6 >> #22 @ start of kernel section
or r1, r7, r6 << #22 @ flags + kernel base
stw r1, [r4+], r6 << #2 @ identity mapping
/*
* Now setup the pagetables for our kernel direct
* mapped region.
*/
add r0, r4, #(KERNEL_START & 0xff000000) >> 20
stw.w r1, [r0+], #(KERNEL_START & 0x00c00000) >> 20
movl r6, #(KERNEL_END - 1)
add r0, r0, #4
add r6, r4, r6 >> #20
102: csub.a r0, r6
add r1, r1, #1 << 22
bua 103f
stw.w r1, [r0]+, #4
b 102b
103:
/*
* Then map first 4MB of ram in case it contains our boot params.
*/
add r0, r4, #PAGE_OFFSET >> 20
or r6, r7, #(PHYS_OFFSET & 0xffc00000)
stw r6, [r0]
ldw r15, __switch_data @ address to jump to after
/*
* Initialise TLB, Caches, and MMU state ready to switch the MMU
* on.
*/
mov r0, #0
movc p0.c5, r0, #28 @ cache invalidate all
nop8
movc p0.c6, r0, #6 @ TLB invalidate all
nop8
/*
* ..V. .... ..TB IDAM
* ..1. .... ..01 1111
*/
movl r0, #0x201f @ control register setting
/*
* Setup common bits before finally enabling the MMU. Essentially
* this is just loading the page table pointer and domain access
* registers.
*/
#ifndef CONFIG_ALIGNMENT_TRAP
andn r0, r0, #CR_A
#endif
#ifdef CONFIG_CPU_DCACHE_DISABLE
andn r0, r0, #CR_D
#endif
#ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
andn r0, r0, #CR_B
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
andn r0, r0, #CR_I
#endif
movc p0.c2, r4, #0 @ set pgd
b __turn_mmu_on
ENDPROC(stext)
/*
* Enable the MMU. This completely changes the structure of the visible
* memory space. You will not be able to trace execution through this.
*
* r0 = cp#0 control register
* r15 = *virtual* address to jump to upon completion
*/
.align 5
__turn_mmu_on:
mov r0, r0
movc p0.c1, r0, #0 @ write control reg
nop @ fetch inst by phys addr
mov pc, r15
nop8 @ fetch inst by phys addr
ENDPROC(__turn_mmu_on)
/*
* Setup the initial page tables. We only setup the barest
* amount which are required to get the kernel running, which
* generally means mapping in the kernel code.
*
* r9 = cpuid
* r10 = procinfo
*
* Returns:
* r0, r3, r6, r7 corrupted
* r4 = physical page table address
*/
.ltorg
.align 2
.type __switch_data, %object
__switch_data:
.long __mmap_switched
.long __bss_start @ r6
.long _end @ r7
.long cr_alignment @ r8
.long init_thread_union + THREAD_START_SP @ sp
/*
* The following fragment of code is executed with the MMU on in MMU mode,
* and uses absolute addresses; this is not position independent.
*
* r0 = cp#0 control register
*/
__mmap_switched:
adr r3, __switch_data + 4
ldm.w (r6, r7, r8), [r3]+
ldw sp, [r3]
mov fp, #0 @ Clear BSS (and zero fp)
203: csub.a r6, r7
bea 204f
stw.w fp, [r6]+,#4
b 203b
204:
andn r1, r0, #CR_A @ Clear 'A' bit
stm (r0, r1), [r8]+ @ Save control register values
b start_kernel
ENDPROC(__mmap_switched)
/*
* Exception handling. Something went wrong and we can't proceed. We
* ought to tell the user, but since we don't have any guarantee that
* we're even running on the right architecture, we do virtually nothing.
*
* If CONFIG_DEBUG_LL is set we try to print out something about the error
* and hope for the best (useful if bootloader fails to pass a proper
* machine ID for example).
*/
__error_p:
#ifdef CONFIG_DEBUG_LL
adr r0, str_p1
b.l printascii
mov r0, r9
b.l printhex8
adr r0, str_p2
b.l printascii
901: nop8
b 901b
str_p1: .asciz "\nError: unrecognized processor variant (0x"
str_p2: .asciz ").\n"
.align
#endif
ENDPROC(__error_p)
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