/* $Id: head.S,v 1.7 2003/09/01 17:58:19 lethal Exp $
*
* arch/sh/kernel/head.S
*
* Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
* Copyright (C) 2010 Matt Fleming
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Head.S contains the SH exception handlers and startup code.
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/thread_info.h>
#include <asm/mmu.h>
#include <cpu/mmu_context.h>
#ifdef CONFIG_CPU_SH4A
#define SYNCO() synco
#define PREFI(label, reg) \
mov.l label, reg; \
prefi @reg
#else
#define SYNCO()
#define PREFI(label, reg)
#endif
.section .empty_zero_page, "aw"
ENTRY(empty_zero_page)
.long 1 /* MOUNT_ROOT_RDONLY */
.long 0 /* RAMDISK_FLAGS */
.long 0x0200 /* ORIG_ROOT_DEV */
.long 1 /* LOADER_TYPE */
.long 0x00000000 /* INITRD_START */
.long 0x00000000 /* INITRD_SIZE */
#ifdef CONFIG_32BIT
.long 0x53453f00 + 32 /* "SE?" = 32 bit */
#else
.long 0x53453f00 + 29 /* "SE?" = 29 bit */
#endif
1:
.skip PAGE_SIZE - empty_zero_page - 1b
__HEAD
/*
* Condition at the entry of _stext:
*
* BSC has already been initialized.
* INTC may or may not be initialized.
* VBR may or may not be initialized.
* MMU may or may not be initialized.
* Cache may or may not be initialized.
* Hardware (including on-chip modules) may or may not be initialized.
*
*/
ENTRY(_stext)
! Initialize Status Register
mov.l 1f, r0 ! MD=1, RB=0, BL=0, IMASK=0xF
ldc r0, sr
! Initialize global interrupt mask
#ifdef CONFIG_CPU_HAS_SR_RB
mov #0, r0
ldc r0, r6_bank
#endif
/*
* Prefetch if possible to reduce cache miss penalty.
*
* We do this early on for SH-4A as a micro-optimization,
* as later on we will have speculative execution enabled
* and this will become less of an issue.
*/
PREFI(5f, r0)
PREFI(6f, r0)
!
mov.l 2f, r0
mov r0, r15 ! Set initial r15 (stack pointer)
#ifdef CONFIG_CPU_HAS_SR_RB
mov.l 7f, r0
ldc r0, r7_bank ! ... and initial thread_info
#endif
#ifdef CONFIG_PMB
/*
* Reconfigure the initial PMB mappings setup by the hardware.
*
* When we boot in 32-bit MMU mode there are 2 PMB entries already
* setup for us.
*
* Entry VPN PPN V SZ C UB WT
* ---------------------------------------------------------------
* 0 0x80000000 0x00000000 1 512MB 1 0 1
* 1 0xA0000000 0x00000000 1 512MB 0 0 0
*
* But we reprogram them here because we want complete control over
* our address space and the initial mappings may not map PAGE_OFFSET
* to __MEMORY_START (or even map all of our RAM).
*
* Once we've setup cached and uncached mappings we clear the rest of the
* PMB entries. This clearing also deals with the fact that PMB entries
* can persist across reboots. The PMB could have been left in any state
* when the reboot occurred, so to be safe we clear all entries and start
* with with a clean slate.
*
* The uncached mapping is constructed using the smallest possible
* mapping with a single unbufferable page. Only the kernel text needs to
* be covered via the uncached mapping so that certain functions can be
* run uncached.
*
* Drivers and the like that have previously abused the 1:1 identity
* mapping are unsupported in 32-bit mode and must specify their caching
* preference when page tables are constructed.
*
* This frees up the P2 space for more nefarious purposes.
*
* Register utilization is as follows:
*
* r0 = PMB_DATA data field
* r1 = PMB_DATA address field
* r2 = PMB_ADDR data field
* r3 = PMB_ADDR address field
* r4 = PMB_E_SHIFT
* r5 = remaining amount of RAM to map
* r6 = PMB mapping size we're trying to use
* r7 = cached_to_uncached
* r8 = scratch register
* r9 = scratch register
* r10 = number of PMB entries we've setup
*/
mov.l .LMMUCR, r1 /* Flush the TLB */
mov.l @r1, r0
or #MMUCR_TI, r0
mov.l r0, @r1
mov.l .LMEMORY_SIZE, r5
mov #PMB_E_SHIFT, r0
mov #0x1, r4
shld r0, r4
mov.l .LFIRST_DATA_ENTRY, r0
mov.l .LPMB_DATA, r1
mov.l .LFIRST_ADDR_ENTRY, r2
mov.l .LPMB_ADDR, r3
/*
* First we need to walk the PMB and figure out if there are any
* existing mappings that match the initial mappings VPN/PPN.
* If these have already been established by the bootloader, we
* don't bother setting up new entries here, and let the late PMB
* initialization take care of things instead.
*
* Note that we may need to coalesce and merge entries in order
* to reclaim more available PMB slots, which is much more than
* we want to do at this early stage.
*/
mov #0, r10
mov #NR_PMB_ENTRIES, r9
mov r1, r7 /* temporary PMB_DATA iter */
.Lvalidate_existing_mappings:
mov.l @r7, r8
and r0, r8
cmp/eq r0, r8 /* Check for valid __MEMORY_START mappings */
bt .Lpmb_done
add #1, r10 /* Increment the loop counter */
cmp/eq r9, r10
bf/s .Lvalidate_existing_mappings
add r4, r7 /* Increment to the next PMB_DATA entry */
/*
* If we've fallen through, continue with setting up the initial
* mappings.
*/
mov r5, r7 /* cached_to_uncached */
mov #0, r10
#ifdef CONFIG_UNCACHED_MAPPING
/*
* Uncached mapping
*/
mov #(PMB_SZ_16M >> 2), r9
shll2 r9
mov #(PMB_UB >> 8), r8
shll8 r8
or r0, r8
or r9, r8
mov.l r8, @r1
mov r2, r8
add r7, r8
mov.l r8, @r3
add r4, r1
add r4, r3
add #1, r10
#endif
/*
* Iterate over all of the available sizes from largest to
* smallest for constructing the cached mapping.
*/
#define __PMB_ITER_BY_SIZE(size) \
.L##size: \
mov #(size >> 4), r6; \
shll16 r6; \
shll8 r6; \
\
cmp/hi r5, r6; \
bt 9999f; \
\
mov #(PMB_SZ_##size##M >> 2), r9; \
shll2 r9; \
\
/* \
* Cached mapping \
*/ \
mov #PMB_C, r8; \
or r0, r8; \
or r9, r8; \
mov.l r8, @r1; \
mov.l r2, @r3; \
\
/* Increment to the next PMB_DATA entry */ \
add r4, r1; \
/* Increment to the next PMB_ADDR entry */ \
add r4, r3; \
/* Increment number of PMB entries */ \
add #1, r10; \
\
sub r6, r5; \
add r6, r0; \
add r6, r2; \
\
bra .L##size; \
9999:
__PMB_ITER_BY_SIZE(512)
__PMB_ITER_BY_SIZE(128)
__PMB_ITER_BY_SIZE(64)
__PMB_ITER_BY_SIZE(16)
#ifdef CONFIG_UNCACHED_MAPPING
/*
* Now that we can access it, update cached_to_uncached and
* uncached_size.
*/
mov.l .Lcached_to_uncached, r0
mov.l r7, @r0
mov.l .Luncached_size, r0
mov #1, r7
shll16 r7
shll8 r7
mov.l r7, @r0
#endif
/*
* Clear the remaining PMB entries.
*
* r3 = entry to begin clearing from
* r10 = number of entries we've setup so far
*/
mov #0, r1
mov #NR_PMB_ENTRIES, r0
.Lagain:
mov.l r1, @r3 /* Clear PMB_ADDR entry */
add #1, r10 /* Increment the loop counter */
cmp/eq r0, r10
bf/s .Lagain
add r4, r3 /* Increment to the next PMB_ADDR entry */
mov.l 6f, r0
icbi @r0
.Lpmb_done:
#endif /* CONFIG_PMB */
#ifndef CONFIG_SH_NO_BSS_INIT
/*
* Don't clear BSS if running on slow platforms such as an RTL simulation,
* remote memory via SHdebug link, etc. For these the memory can be guaranteed
* to be all zero on boot anyway.
*/
! Clear BSS area
#ifdef CONFIG_SMP
mov.l 3f, r0
cmp/eq #0, r0 ! skip clear if set to zero
bt 10f
#endif
mov.l 3f, r1
add #4, r1
mov.l 4f, r2
mov #0, r0
9: cmp/hs r2, r1
bf/s 9b ! while (r1 < r2)
mov.l r0,@-r2
10:
#endif
! Additional CPU initialization
mov.l 6f, r0
jsr @r0
nop
SYNCO() ! Wait for pending instructions..
! Start kernel
mov.l 5f, r0
jmp @r0
nop
.balign 4
#if defined(CONFIG_CPU_SH2)
1: .long 0x000000F0 ! IMASK=0xF
#else
1: .long 0x400080F0 ! MD=1, RB=0, BL=0, FD=1, IMASK=0xF
#endif
ENTRY(stack_start)
2: .long init_thread_union+THREAD_SIZE
3: .long __bss_start
4: .long _end
5: .long start_kernel
6: .long sh_cpu_init
7: .long init_thread_union
#ifdef CONFIG_PMB
.LPMB_ADDR: .long PMB_ADDR
.LPMB_DATA: .long PMB_DATA
.LFIRST_ADDR_ENTRY: .long PAGE_OFFSET | PMB_V
.LFIRST_DATA_ENTRY: .long __MEMORY_START | PMB_V
.LMMUCR: .long MMUCR
.LMEMORY_SIZE: .long __MEMORY_SIZE
#ifdef CONFIG_UNCACHED_MAPPING
.Lcached_to_uncached: .long cached_to_uncached
.Luncached_size: .long uncached_size
#endif
#endif
