diff options
Diffstat (limited to 'arch/sh/kernel/head_32.S')
| -rw-r--r-- | arch/sh/kernel/head_32.S | 365 |
1 files changed, 365 insertions, 0 deletions
diff --git a/arch/sh/kernel/head_32.S b/arch/sh/kernel/head_32.S new file mode 100644 index 000000000..b603b7968 --- /dev/null +++ b/arch/sh/kernel/head_32.S @@ -0,0 +1,365 @@ +/* SPDX-License-Identifier: GPL-2.0 + * $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 + * + * 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 + +#ifdef CONFIG_OF_EARLY_FLATTREE + mov r4, r12 ! Store device tree blob pointer in r12 +#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 + * r11 = scratch register + */ + + 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 .LPMB_DATA_MASK, r11 + mov.l @r7, r8 + and r11, 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 + +#ifdef CONFIG_OF_EARLY_FLATTREE + mov.l 8f, r0 ! Make flat device tree available early. + jsr @r0 + mov r12, r4 +#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 0x500080F0 ! MD=1, RB=0, BL=1, 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 cpu_init +7: .long init_thread_union +#if defined(CONFIG_OF_EARLY_FLATTREE) +8: .long sh_fdt_init +#endif + +#ifdef CONFIG_PMB +.LPMB_ADDR: .long PMB_ADDR +.LPMB_DATA: .long PMB_DATA +.LPMB_DATA_MASK: .long PMB_PFN_MASK | PMB_V +.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 |