riscv: cpu: Add nx25 to support RISC-V

Add Andes nx25 cpu core (called AndesStar V5) to support RISC-V arch

Verifications:
1. startup and relocation ok.
2. boot from rom or ram both ok.
2. timer driver ok.
3. uart driver ok
4. mmc driver ok
5. spi driver ok.
6. 32/64 bit both ok.

Detail verification message please see doc/README.ae250.

Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Signed-off-by: Greentime Hu <green.hu@gmail.com>
Cc: Padmarao Begari <Padmarao.Begari@microsemi.com>

1 files changed, 291 insertions, 0 deletions

diff --git a/arch/riscv/cpu/nx25/start.S b/arch/riscv/cpu/nx25/start.S
new file mode 100644
index 0000000000..6a076639d3
--- /dev/null
+++ b/arch/riscv/cpu/nx25/start.S
@@ -0,0 +1,291 @@
+/*
+ * 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>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#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:
+	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