1/*
  2 * Copyright (C) 2012 Regents of the University of California
  3 *
  4 *   This program is free software; you can redistribute it and/or
  5 *   modify it under the terms of the GNU General Public License
  6 *   as published by the Free Software Foundation, version 2.
  7 *
  8 *   This program is distributed in the hope that it will be useful,
  9 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 10 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11 *   GNU General Public License for more details.
 12 */
 13
 14#include <asm/thread_info.h>
 15#include <asm/asm-offsets.h>
 16#include <asm/asm.h>
 17#include <linux/init.h>
 18#include <linux/linkage.h>
 19#include <asm/thread_info.h>
 20#include <asm/page.h>
 21#include <asm/csr.h>
 22
 23__INIT
 24ENTRY(_start)
 25	/* Mask all interrupts */
 26	csrw sie, zero
 27
 28	/* Load the global pointer */
 29.option push
 30.option norelax
 31	la gp, __global_pointer$
 32.option pop
 33
 34	/*
 35	 * Disable FPU to detect illegal usage of
 36	 * floating point in kernel space
 37	 */
 38	li t0, SR_FS
 39	csrc sstatus, t0
 40
 41	/* Pick one hart to run the main boot sequence */
 42	la a3, hart_lottery
 43	li a2, 1
 44	amoadd.w a3, a2, (a3)
 45	bnez a3, .Lsecondary_start
 46
 47	/* Save hart ID and DTB physical address */
 48	mv s0, a0
 49	mv s1, a1
 50
 51	/* Initialize page tables and relocate to virtual addresses */
 52	la sp, init_thread_union + THREAD_SIZE
 53	call setup_vm
 54	call relocate
 55
 56	/* Restore C environment */
 57	la tp, init_task
 58	sw s0, TASK_TI_CPU(tp)
 59
 60	la sp, init_thread_union
 61	li a0, ASM_THREAD_SIZE
 62	add sp, sp, a0
 63
 64	/* Start the kernel */
 65	mv a0, s0
 66	mv a1, s1
 67	call parse_dtb
 68	tail start_kernel
 69
 70relocate:
 71	/* Relocate return address */
 72	li a1, PAGE_OFFSET
 73	la a0, _start
 74	sub a1, a1, a0
 75	add ra, ra, a1
 76
 77	/* Point stvec to virtual address of intruction after satp write */
 78	la a0, 1f
 79	add a0, a0, a1
 80	csrw stvec, a0
 81
 82	/* Compute satp for kernel page tables, but don't load it yet */
 83	la a2, swapper_pg_dir
 84	srl a2, a2, PAGE_SHIFT
 85	li a1, SATP_MODE
 86	or a2, a2, a1
 87
 88	/*
 89	 * Load trampoline page directory, which will cause us to trap to
 90	 * stvec if VA != PA, or simply fall through if VA == PA
 91	 */
 92	la a0, trampoline_pg_dir
 93	srl a0, a0, PAGE_SHIFT
 94	or a0, a0, a1
 95	sfence.vma
 96	csrw sptbr, a0
 971:
 98	/* Set trap vector to spin forever to help debug */
 99	la a0, .Lsecondary_park
100	csrw stvec, a0
101
102	/* Reload the global pointer */
103.option push
104.option norelax
105	la gp, __global_pointer$
106.option pop
107
108	/* Switch to kernel page tables */
109	csrw sptbr, a2
110
111	ret
112
113.Lsecondary_start:
114#ifdef CONFIG_SMP
115	li a1, CONFIG_NR_CPUS
116	bgeu a0, a1, .Lsecondary_park
117
118	/* Set trap vector to spin forever to help debug */
119	la a3, .Lsecondary_park
120	csrw stvec, a3
121
122	slli a3, a0, LGREG
123	la a1, __cpu_up_stack_pointer
124	la a2, __cpu_up_task_pointer
125	add a1, a3, a1
126	add a2, a3, a2
127
128	/*
129	 * This hart didn't win the lottery, so we wait for the winning hart to
130	 * get far enough along the boot process that it should continue.
131	 */
132.Lwait_for_cpu_up:
133	/* FIXME: We should WFI to save some energy here. */
134	REG_L sp, (a1)
135	REG_L tp, (a2)
136	beqz sp, .Lwait_for_cpu_up
137	beqz tp, .Lwait_for_cpu_up
138	fence
139
140	/* Enable virtual memory and relocate to virtual address */
141	call relocate
142
143	tail smp_callin
144#endif
145
146.Lsecondary_park:
147	/* We lack SMP support or have too many harts, so park this hart */
148	wfi
149	j .Lsecondary_park
150END(_start)
151
152__PAGE_ALIGNED_BSS
153	/* Empty zero page */
154	.balign PAGE_SIZE