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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* PowerPC version
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
* Rewritten by Cort Dougan (cort@cs.nmt.edu) for PReP
* Copyright (C) 1996 Cort Dougan <cort@cs.nmt.edu>
* Low-level exception handlers and MMU support
* rewritten by Paul Mackerras.
* Copyright (C) 1996 Paul Mackerras.
* MPC8xx modifications by Dan Malek
* Copyright (C) 1997 Dan Malek (dmalek@jlc.net).
*
* This file contains low-level support and setup for PowerPC 8xx
* embedded processors, including trap and interrupt dispatch.
*/
#include <linux/init.h>
#include <linux/magic.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/cache.h>
#include <asm/pgtable.h>
#include <asm/cputable.h>
#include <asm/thread_info.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/ptrace.h>
#include <asm/export.h>
#include <asm/code-patching-asm.h>
#include "head_32.h"
#if CONFIG_TASK_SIZE <= 0x80000000 && CONFIG_PAGE_OFFSET >= 0x80000000
/* By simply checking Address >= 0x80000000, we know if its a kernel address */
#define SIMPLE_KERNEL_ADDRESS 1
#endif
/*
* We need an ITLB miss handler for kernel addresses if:
* - Either we have modules
* - Or we have not pinned the first 8M
*/
#if defined(CONFIG_MODULES) || !defined(CONFIG_PIN_TLB_TEXT) || \
defined(CONFIG_DEBUG_PAGEALLOC)
#define ITLB_MISS_KERNEL 1
#endif
/*
* Value for the bits that have fixed value in RPN entries.
* Also used for tagging DAR for DTLBerror.
*/
#define RPN_PATTERN 0x00f0
#define PAGE_SHIFT_512K 19
#define PAGE_SHIFT_8M 23
__HEAD
_ENTRY(_stext);
_ENTRY(_start);
/* MPC8xx
* This port was done on an MBX board with an 860. Right now I only
* support an ELF compressed (zImage) boot from EPPC-Bug because the
* code there loads up some registers before calling us:
* r3: ptr to board info data
* r4: initrd_start or if no initrd then 0
* r5: initrd_end - unused if r4 is 0
* r6: Start of command line string
* r7: End of command line string
*
* I decided to use conditional compilation instead of checking PVR and
* adding more processor specific branches around code I don't need.
* Since this is an embedded processor, I also appreciate any memory
* savings I can get.
*
* The MPC8xx does not have any BATs, but it supports large page sizes.
* We first initialize the MMU to support 8M byte pages, then load one
* entry into each of the instruction and data TLBs to map the first
* 8M 1:1. I also mapped an additional I/O space 1:1 so we can get to
* the "internal" processor registers before MMU_init is called.
*
* -- Dan
*/
.globl __start
__start:
mr r31,r3 /* save device tree ptr */
/* We have to turn on the MMU right away so we get cache modes
* set correctly.
*/
bl initial_mmu
/* We now have the lower 8 Meg mapped into TLB entries, and the caches
* ready to work.
*/
turn_on_mmu:
mfmsr r0
ori r0,r0,MSR_DR|MSR_IR
mtspr SPRN_SRR1,r0
lis r0,start_here@h
ori r0,r0,start_here@l
mtspr SPRN_SRR0,r0
rfi /* enables MMU */
#ifdef CONFIG_PERF_EVENTS
.align 4
.globl itlb_miss_counter
itlb_miss_counter:
.space 4
.globl dtlb_miss_counter
dtlb_miss_counter:
.space 4
.globl instruction_counter
instruction_counter:
.space 4
#endif
/* System reset */
EXCEPTION(0x100, Reset, system_reset_exception, EXC_XFER_STD)
/* Machine check */
. = 0x200
MachineCheck:
EXCEPTION_PROLOG
mfspr r4,SPRN_DAR
stw r4,_DAR(r11)
li r5,RPN_PATTERN
mtspr SPRN_DAR,r5 /* Tag DAR, to be used in DTLB Error */
mfspr r5,SPRN_DSISR
stw r5,_DSISR(r11)
addi r3,r1,STACK_FRAME_OVERHEAD
EXC_XFER_STD(0x200, machine_check_exception)
/* Data access exception.
* This is "never generated" by the MPC8xx.
*/
. = 0x300
DataAccess:
/* Instruction access exception.
* This is "never generated" by the MPC8xx.
*/
. = 0x400
InstructionAccess:
/* External interrupt */
EXCEPTION(0x500, HardwareInterrupt, do_IRQ, EXC_XFER_LITE)
/* Alignment exception */
. = 0x600
Alignment:
EXCEPTION_PROLOG
mfspr r4,SPRN_DAR
stw r4,_DAR(r11)
li r5,RPN_PATTERN
mtspr SPRN_DAR,r5 /* Tag DAR, to be used in DTLB Error */
mfspr r5,SPRN_DSISR
stw r5,_DSISR(r11)
addi r3,r1,STACK_FRAME_OVERHEAD
EXC_XFER_STD(0x600, alignment_exception)
/* Program check exception */
EXCEPTION(0x700, ProgramCheck, program_check_exception, EXC_XFER_STD)
/* No FPU on MPC8xx. This exception is not supposed to happen.
*/
EXCEPTION(0x800, FPUnavailable, unknown_exception, EXC_XFER_STD)
/* Decrementer */
EXCEPTION(0x900, Decrementer, timer_interrupt, EXC_XFER_LITE)
EXCEPTION(0xa00, Trap_0a, unknown_exception, EXC_XFER_STD)
EXCEPTION(0xb00, Trap_0b, unknown_exception, EXC_XFER_STD)
/* System call */
. = 0xc00
SystemCall:
SYSCALL_ENTRY 0xc00
/* Single step - not used on 601 */
EXCEPTION(0xd00, SingleStep, single_step_exception, EXC_XFER_STD)
EXCEPTION(0xe00, Trap_0e, unknown_exception, EXC_XFER_STD)
EXCEPTION(0xf00, Trap_0f, unknown_exception, EXC_XFER_STD)
/* On the MPC8xx, this is a software emulation interrupt. It occurs
* for all unimplemented and illegal instructions.
*/
EXCEPTION(0x1000, SoftEmu, program_check_exception, EXC_XFER_STD)
/* Called from DataStoreTLBMiss when perf TLB misses events are activated */
#ifdef CONFIG_PERF_EVENTS
patch_site 0f, patch__dtlbmiss_perf
0: lwz r10, (dtlb_miss_counter - PAGE_OFFSET)@l(0)
addi r10, r10, 1
stw r10, (dtlb_miss_counter - PAGE_OFFSET)@l(0)
mfspr r10, SPRN_SPRG_SCRATCH0
mfspr r11, SPRN_SPRG_SCRATCH1
rfi
#endif
. = 0x1100
/*
* For the MPC8xx, this is a software tablewalk to load the instruction
* TLB. The task switch loads the M_TWB register with the pointer to the first
* level table.
* If we discover there is no second level table (value is zero) or if there
* is an invalid pte, we load that into the TLB, which causes another fault
* into the TLB Error interrupt where we can handle such problems.
* We have to use the MD_xxx registers for the tablewalk because the
* equivalent MI_xxx registers only perform the attribute functions.
*/
#ifdef CONFIG_8xx_CPU15
#define INVALIDATE_ADJACENT_PAGES_CPU15(addr) \
addi addr, addr, PAGE_SIZE; \
tlbie addr; \
addi addr, addr, -(PAGE_SIZE << 1); \
tlbie addr; \
addi addr, addr, PAGE_SIZE
#else
#define INVALIDATE_ADJACENT_PAGES_CPU15(addr)
#endif
InstructionTLBMiss:
mtspr SPRN_SPRG_SCRATCH0, r10
#if defined(ITLB_MISS_KERNEL) || defined(CONFIG_SWAP)
mtspr SPRN_SPRG_SCRATCH1, r11
#endif
/* If we are faulting a kernel address, we have to use the
* kernel page tables.
*/
mfspr r10, SPRN_SRR0 /* Get effective address of fault */
INVALIDATE_ADJACENT_PAGES_CPU15(r10)
mtspr SPRN_MD_EPN, r10
/* Only modules will cause ITLB Misses as we always
* pin the first 8MB of kernel memory */
#ifdef ITLB_MISS_KERNEL
mfcr r11
#if defined(SIMPLE_KERNEL_ADDRESS) && defined(CONFIG_PIN_TLB_TEXT)
cmpi cr0, r10, 0 /* Address >= 0x80000000 */
#else
rlwinm r10, r10, 16, 0xfff8
cmpli cr0, r10, PAGE_OFFSET@h
#ifndef CONFIG_PIN_TLB_TEXT
/* It is assumed that kernel code fits into the first 32M */
0: cmpli cr7, r10, (PAGE_OFFSET + 0x2000000)@h
patch_site 0b, patch__itlbmiss_linmem_top
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