1 /* $Id: head.S,v 1.7 2003/09/01 17:58:19 lethal Exp $
3 * arch/sh/kernel/head.S
5 * Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
6 * Copyright (C) 2010 Matt Fleming
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License. See the file "COPYING" in the main directory of this archive
12 * Head.S contains the SH exception handlers and startup code.
14 #include <linux/init.h>
15 #include <linux/linkage.h>
16 #include <asm/thread_info.h>
18 #include <cpu/mmu_context.h>
20 #ifdef CONFIG_CPU_SH4A
23 #define PREFI(label, reg) \
28 #define PREFI(label, reg)
31 .section .empty_zero_page, "aw"
32 ENTRY(empty_zero_page)
33 .long 1 /* MOUNT_ROOT_RDONLY */
34 .long 0 /* RAMDISK_FLAGS */
35 .long 0x0200 /* ORIG_ROOT_DEV */
36 .long 1 /* LOADER_TYPE */
37 .long 0x00000000 /* INITRD_START */
38 .long 0x00000000 /* INITRD_SIZE */
40 .long 0x53453f00 + 32 /* "SE?" = 32 bit */
42 .long 0x53453f00 + 29 /* "SE?" = 29 bit */
45 .skip PAGE_SIZE - empty_zero_page - 1b
50 * Condition at the entry of _stext:
52 * BSC has already been initialized.
53 * INTC may or may not be initialized.
54 * VBR may or may not be initialized.
55 * MMU may or may not be initialized.
56 * Cache may or may not be initialized.
57 * Hardware (including on-chip modules) may or may not be initialized.
61 ! Initialize Status Register
62 mov.l 1f, r0 ! MD=1, RB=0, BL=0, IMASK=0xF
64 ! Initialize global interrupt mask
65 #ifdef CONFIG_CPU_HAS_SR_RB
71 * Prefetch if possible to reduce cache miss penalty.
73 * We do this early on for SH-4A as a micro-optimization,
74 * as later on we will have speculative execution enabled
75 * and this will become less of an issue.
82 mov r0, r15 ! Set initial r15 (stack pointer)
83 #ifdef CONFIG_CPU_HAS_SR_RB
85 ldc r0, r7_bank ! ... and initial thread_info
90 * Reconfigure the initial PMB mappings setup by the hardware.
92 * When we boot in 32-bit MMU mode there are 2 PMB entries already
95 * Entry VPN PPN V SZ C UB WT
96 * ---------------------------------------------------------------
97 * 0 0x80000000 0x00000000 1 512MB 1 0 1
98 * 1 0xA0000000 0x00000000 1 512MB 0 0 0
100 * But we reprogram them here because we want complete control over
101 * our address space and the initial mappings may not map PAGE_OFFSET
102 * to __MEMORY_START (or even map all of our RAM).
104 * Once we've setup cached and uncached mappings we clear the rest of the
105 * PMB entries. This clearing also deals with the fact that PMB entries
106 * can persist across reboots. The PMB could have been left in any state
107 * when the reboot occurred, so to be safe we clear all entries and start
108 * with with a clean slate.
110 * The uncached mapping is constructed using the smallest possible
111 * mapping with a single unbufferable page. Only the kernel text needs to
112 * be covered via the uncached mapping so that certain functions can be
115 * Drivers and the like that have previously abused the 1:1 identity
116 * mapping are unsupported in 32-bit mode and must specify their caching
117 * preference when page tables are constructed.
119 * This frees up the P2 space for more nefarious purposes.
121 * Register utilization is as follows:
123 * r0 = PMB_DATA data field
124 * r1 = PMB_DATA address field
125 * r2 = PMB_ADDR data field
126 * r3 = PMB_ADDR address field
128 * r5 = remaining amount of RAM to map
129 * r6 = PMB mapping size we're trying to use
130 * r7 = cached_to_uncached
131 * r8 = scratch register
132 * r9 = scratch register
133 * r10 = number of PMB entries we've setup
136 mov.l .LMMUCR, r1 /* Flush the TLB */
141 mov.l .LMEMORY_SIZE, r5
147 mov.l .LFIRST_DATA_ENTRY, r0
149 mov.l .LFIRST_ADDR_ENTRY, r2
153 * First we need to walk the PMB and figure out if there are any
154 * existing mappings that match the initial mappings VPN/PPN.
155 * If these have already been established by the bootloader, we
156 * don't bother setting up new entries here, and let the late PMB
157 * initialization take care of things instead.
159 * Note that we may need to coalesce and merge entries in order
160 * to reclaim more available PMB slots, which is much more than
161 * we want to do at this early stage.
164 mov #NR_PMB_ENTRIES, r9
166 mov r1, r7 /* temporary PMB_DATA iter */
168 .Lvalidate_existing_mappings:
172 cmp/eq r0, r8 /* Check for valid __MEMORY_START mappings */
175 add #1, r10 /* Increment the loop counter */
177 bf/s .Lvalidate_existing_mappings
178 add r4, r7 /* Increment to the next PMB_DATA entry */
181 * If we've fallen through, continue with setting up the initial
185 mov r5, r7 /* cached_to_uncached */
188 #ifdef CONFIG_UNCACHED_MAPPING
192 mov #(PMB_SZ_16M >> 2), r9
195 mov #(PMB_UB >> 8), r8
211 * Iterate over all of the available sizes from largest to
212 * smallest for constructing the cached mapping.
214 #define __PMB_ITER_BY_SIZE(size) \
216 mov #(size >> 4), r6; \
223 mov #(PMB_SZ_##size##M >> 2), r9; \
235 /* Increment to the next PMB_DATA entry */ \
237 /* Increment to the next PMB_ADDR entry */ \
239 /* Increment number of PMB entries */ \
249 __PMB_ITER_BY_SIZE(512)
250 __PMB_ITER_BY_SIZE(128)
251 __PMB_ITER_BY_SIZE(64)
252 __PMB_ITER_BY_SIZE(16)
254 #ifdef CONFIG_UNCACHED_MAPPING
256 * Now that we can access it, update cached_to_uncached and
259 mov.l .Lcached_to_uncached, r0
262 mov.l .Luncached_size, r0
270 * Clear the remaining PMB entries.
272 * r3 = entry to begin clearing from
273 * r10 = number of entries we've setup so far
276 mov #NR_PMB_ENTRIES, r0
279 mov.l r1, @r3 /* Clear PMB_ADDR entry */
280 add #1, r10 /* Increment the loop counter */
283 add r4, r3 /* Increment to the next PMB_ADDR entry */
289 #endif /* CONFIG_PMB */
291 #ifndef CONFIG_SH_NO_BSS_INIT
293 * Don't clear BSS if running on slow platforms such as an RTL simulation,
294 * remote memory via SHdebug link, etc. For these the memory can be guaranteed
295 * to be all zero on boot anyway.
300 cmp/eq #0, r0 ! skip clear if set to zero
309 bf/s 9b ! while (r1 < r2)
315 ! Additional CPU initialization
320 SYNCO() ! Wait for pending instructions..
328 #if defined(CONFIG_CPU_SH2)
329 1: .long 0x000000F0 ! IMASK=0xF
331 1: .long 0x400080F0 ! MD=1, RB=0, BL=0, FD=1, IMASK=0xF
334 2: .long init_thread_union+THREAD_SIZE
337 5: .long start_kernel
339 7: .long init_thread_union
342 .LPMB_ADDR: .long PMB_ADDR
343 .LPMB_DATA: .long PMB_DATA
344 .LFIRST_ADDR_ENTRY: .long PAGE_OFFSET | PMB_V
345 .LFIRST_DATA_ENTRY: .long __MEMORY_START | PMB_V
347 .LMEMORY_SIZE: .long __MEMORY_SIZE
348 #ifdef CONFIG_UNCACHED_MAPPING
349 .Lcached_to_uncached: .long cached_to_uncached
350 .Luncached_size: .long uncached_size