arch/riscv/cpu/start.S

/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * Startup Code for RISC-V Core
 *
 * Copyright (c) 2017 Microsemi Corporation.
 * Copyright (c) 2017 Padmarao Begari <Padmarao.Begari@microsemi.com>
 *
 * Copyright (C) 2017 Andes Technology Corporation
 * Rick Chen, Andes Technology Corporation <rick@andestech.com>
 */

#include <asm-offsets.h>
#include <config.h>
#include <common.h>
#include <elf.h>
#include <asm/encoding.h>

#ifdef CONFIG_32BIT
#define LREG 			lw
#define SREG 			sw
#define REGBYTES 		4
#define RELOC_TYPE		R_RISCV_32
#define SYM_INDEX		0x8
#define SYM_SIZE		0x10
#else
#define LREG 			ld
#define SREG 			sd
#define REGBYTES 		8
#define RELOC_TYPE		R_RISCV_64
#define SYM_INDEX		0x20
#define SYM_SIZE		0x18
#endif

.section      .text
.globl _start
_start:
	j handle_reset

nmi_vector:
	j nmi_vector

trap_vector:
	j trap_entry

.global trap_entry
handle_reset:
	li t0, CONFIG_SYS_SDRAM_BASE
	SREG a2, 0(t0)
	la t0, trap_entry
	csrw mtvec, t0
	csrwi mstatus, 0
	csrwi mie, 0

/*
 * Do CPU critical regs init only at reboot,
 * not when booting from ram
 */
#ifdef CONFIG_INIT_CRITICAL
	jal cpu_init_crit	/* Do CPU critical regs init */
#endif

/*
 * Set stackpointer in internal/ex RAM to call board_init_f
 */
call_board_init_f:
	li  t0, -16
	li  t1, CONFIG_SYS_INIT_SP_ADDR
	and sp, t1, t0	/* force 16 byte alignment */

#ifdef CONFIG_DEBUG_UART
	jal	debug_uart_init
#endif

call_board_init_f_0:
	mv	a0, sp
	jal	board_init_f_alloc_reserve
	mv	sp, a0
	jal	board_init_f_init_reserve

	mv  a0, zero	/* a0 <-- boot_flags = 0 */
	la t5, board_init_f
	jr t5		/* jump to board_init_f() */

/*
 * void relocate_code (addr_sp, gd, addr_moni)
 *
 * This "function" does not return, instead it continues in RAM
 * after relocating the monitor code.
 *
 */
.globl relocate_code
relocate_code:
	mv  s2, a0	/* save addr_sp */
	mv  s3, a1	/* save addr of gd */
	mv  s4, a2	/* save addr of destination */

/*
 *Set up the stack
 */
stack_setup:
	mv sp, s2
	la t0, _start
	sub t6, s4, t0	/* t6 <- relocation offset */
	beq t0, s4, clear_bss	/* skip relocation */

	mv t1, s4	/* t1 <- scratch for copy_loop */
	la t3, __bss_start
	sub t3, t3, t0	/* t3 <- __bss_start_ofs */
	add t2, t0, t3	/* t2 <- source end address */

copy_loop:
	LREG t5, 0(t0)
	addi t0, t0, REGBYTES
	SREG t5, 0(t1)
	addi t1, t1, REGBYTES
	blt t0, t2, copy_loop

/*
 * Update dynamic relocations after board_init_f
 */
fix_rela_dyn:
	la  t1, __rel_dyn_start
	la  t2, __rel_dyn_end
	beq t1, t2, clear_bss
	add t1, t1, t6			/* t1 <- rela_dyn_start in RAM */
	add t2, t2, t6			/* t2 <- rela_dyn_end in RAM */

/*
 * skip first reserved entry: address, type, addend
 */
	bne t1, t2, 7f

6:
	LREG  t5, -(REGBYTES*2)(t1)	/* t5 <-- relocation info:type */
	li  t3, R_RISCV_RELATIVE	/* reloc type R_RISCV_RELATIVE */
	bne t5, t3, 8f			/* skip non-RISCV_RELOC entries */
	LREG t3, -(REGBYTES*3)(t1)
	LREG t5, -(REGBYTES)(t1)	/* t5 <-- addend */
	add t5, t5, t6			/* t5 <-- location to fix up in RAM */
	add t3, t3, t6			/* t3 <-- location to fix up in RAM */
	SREG t5, 0(t3)
7:
	addi t1, t1, (REGBYTES*3)
	ble t1, t2, 6b

8:
	la  t4, __dyn_sym_start
	add t4, t4, t6

9:
	LREG  t5, -(REGBYTES*2)(t1)	/* t5 <-- relocation info:type */
	srli t0, t5, SYM_INDEX		/* t0 <--- sym table index */
	andi t5, t5, 0xFF		/* t5 <--- relocation type */
	li  t3, RELOC_TYPE
	bne t5, t3, 10f 		/* skip non-addned entries */

	LREG t3, -(REGBYTES*3)(t1)
	li t5, SYM_SIZE
	mul t0, t0, t5
	add s1, t4, t0
	LREG t5, REGBYTES(s1)
	add t5, t5, t6			/* t5 <-- location to fix up in RAM */
	add t3, t3, t6			/* t3 <-- location to fix up in RAM */
	SREG t5, 0(t3)
10:
	addi t1, t1, (REGBYTES*3)
	ble t1, t2, 9b

/*
 * trap update
*/
	la t0, trap_entry
	add t0, t0, t6
	csrw mtvec, t0

clear_bss:
	la t0, __bss_start		/* t0 <- rel __bss_start in FLASH */
	add t0, t0, t6			/* t0 <- rel __bss_start in RAM */
	la t1, __bss_end		/* t1 <- rel __bss_end in FLASH */
	add t1, t1, t6			/* t1 <- rel __bss_end in RAM */
	li t2, 0x00000000		/* clear */
	beq t0, t1, call_board_init_r

clbss_l:
	SREG t2, 0(t0)			/* clear loop... */
	addi t0, t0, REGBYTES
	bne t0, t1, clbss_l

/*
 * We are done. Do not return, instead branch to second part of board
 * initialization, now running from RAM.
 */
call_board_init_r:
	la t0, board_init_r
	mv t4, t0			/* offset of board_init_r() */
	add t4, t4, t6			/* real address of board_init_r() */
/*
 * setup parameters for board_init_r
 */
	mv a0, s3			/* gd_t */
	mv a1, s4			/* dest_addr */

/*
 * jump to it ...
 */
	jr t4				/* jump to board_init_r() */

/*
 * trap entry
 */
trap_entry:
	addi sp, sp, -32*REGBYTES
	SREG x1, 1*REGBYTES(sp)
	SREG x2, 2*REGBYTES(sp)
	SREG x3, 3*REGBYTES(sp)
	SREG x4, 4*REGBYTES(sp)
	SREG x5, 5*REGBYTES(sp)
	SREG x6, 6*REGBYTES(sp)
	SREG x7, 7*REGBYTES(sp)
	SREG x8, 8*REGBYTES(sp)
	SREG x9, 9*REGBYTES(sp)
	SREG x10, 10*REGBYTES(sp)
	SREG x11, 11*REGBYTES(sp)
	SREG x12, 12*REGBYTES(sp)
	SREG x13, 13*REGBYTES(sp)
	SREG x14, 14*REGBYTES(sp)
	SREG x15, 15*REGBYTES(sp)
	SREG x16, 16*REGBYTES(sp)
	SREG x17, 17*REGBYTES(sp)
	SREG x18, 18*REGBYTES(sp)
	SREG x19, 19*REGBYTES(sp)
	SREG x20, 20*REGBYTES(sp)
	SREG x21, 21*REGBYTES(sp)
	SREG x22, 22*REGBYTES(sp)
	SREG x23, 23*REGBYTES(sp)
	SREG x24, 24*REGBYTES(sp)
	SREG x25, 25*REGBYTES(sp)
	SREG x26, 26*REGBYTES(sp)
	SREG x27, 27*REGBYTES(sp)
	SREG x28, 28*REGBYTES(sp)
	SREG x29, 29*REGBYTES(sp)
	SREG x30, 30*REGBYTES(sp)
	SREG x31, 31*REGBYTES(sp)
	csrr a0, mcause
	csrr a1, mepc
	mv a2, sp
	jal handle_trap
	csrw mepc, a0

/*
 * Remain in M-mode after mret
 */
	li t0, MSTATUS_MPP
	csrs mstatus, t0
	LREG x1, 1*REGBYTES(sp)
	LREG x2, 2*REGBYTES(sp)
	LREG x3, 3*REGBYTES(sp)
	LREG x4, 4*REGBYTES(sp)
	LREG x5, 5*REGBYTES(sp)
	LREG x6, 6*REGBYTES(sp)
	LREG x7, 7*REGBYTES(sp)
	LREG x8, 8*REGBYTES(sp)
	LREG x9, 9*REGBYTES(sp)
	LREG x10, 10*REGBYTES(sp)
	LREG x11, 11*REGBYTES(sp)
	LREG x12, 12*REGBYTES(sp)
	LREG x13, 13*REGBYTES(sp)
	LREG x14, 14*REGBYTES(sp)
	LREG x15, 15*REGBYTES(sp)
	LREG x16, 16*REGBYTES(sp)
	LREG x17, 17*REGBYTES(sp)
	LREG x18, 18*REGBYTES(sp)
	LREG x19, 19*REGBYTES(sp)
	LREG x20, 20*REGBYTES(sp)
	LREG x21, 21*REGBYTES(sp)
	LREG x22, 22*REGBYTES(sp)
	LREG x23, 23*REGBYTES(sp)
	LREG x24, 24*REGBYTES(sp)
	LREG x25, 25*REGBYTES(sp)
	LREG x26, 26*REGBYTES(sp)
	LREG x27, 27*REGBYTES(sp)
	LREG x28, 28*REGBYTES(sp)
	LREG x29, 29*REGBYTES(sp)
	LREG x30, 30*REGBYTES(sp)
	LREG x31, 31*REGBYTES(sp)
	addi sp, sp, 32*REGBYTES
	mret

#ifdef CONFIG_INIT_CRITICAL
cpu_init_crit:
    ret
#endif