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linux/arch/sh/kernel/head_32.S
Rich Felker 7480e0aabd sh: add device tree support and generic board using device tree 
Add a new pseudo-board, within the existing SH boards/machine-vectors
framework, which does not represent any actual hardware but instead
requires all hardware to be described by the device tree blob provided
by the boot loader. Changes made are thus non-invasive and do not risk
breaking support for legacy boards.

New hardware, including the open-hardware J2 and associated SoC
devices, will use device free from the outset. Legacy SH boards can
transition to device tree once all their hardware has device tree
bindings, driver support for device tree, and a dts file for the
board.

It is intented that, once all boards are supported in the new
framework, the existing machine-vectors framework should be removed
and the new device tree setup code integrated directly.

Signed-off-by: Rich Felker <dalias@libc.org>
2016-03-17 19:46:11 +00:00

369 lines
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/* $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
#ifdef CONFIG_OF
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
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)
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
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