/*
 * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
 * Copyright (C) 2010 chysun2000@gmail.com
 *
 * This file is part of nios2sim-ng.
 *
 * 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.
 */

#ifndef _NIOS2_H_
#define _NIOS2_H_

#include "instruction.h"
#include "memory.h"

#define NIOS2_GP_REG_COUNT	32
/* there are really 32, but 16-31 are reserved for future use */
#define NIOS2_CTRL_REG_COUNT	16

struct tlb_entry;

struct nios2 {
	/* General-Purpose Registers */
	uint32_t gp_regs[NIOS2_GP_REG_COUNT];
	/* Control Registers */
	uint32_t ctrl_regs[NIOS2_CTRL_REG_COUNT];
	/* Program counter */
	uint32_t pc;
	/* User or Supervisor mode */
	unsigned int mode;
	/* Exception cause */
	unsigned int exception_cause;

	/* Configurable processor features */
	bool has_mul;	/* mul, muli */
	bool has_mulx;	/* mulxss, mulxsu, mulxuu */
	bool has_div;	/* div, divu */

	bool has_mmu;	/* Memory Management Unit */

	/*
	struct tlb_entry tlb[TLB_NUM_LINES][TLB_NUM_WAYS];
	*/

	struct memory *mem;
	/* Exception handler address */
	uint32_t exception_handler_addr;
};

/* processor modes */
enum {
	NIOS2_SUPERVISOR_MODE,
	NIOS2_USER_MODE,	/* only used with MMU */
};

/* Aliases for general-purpose registers */
enum {
	zero = 0,
	at,
	et = 24,
	bt,
	gp,
	sp,
	fp,
	ea,
	ba,
	ra,
};

/* Aliases for control registers */
enum {
	status = 0,
	estatus,
	bstatus,
	ienable,
	ipending,
	cpuid,
	/* reserved */
	exception = 7,
	pteaddr,
	tlbacc,
	tlbmisc,
	/* reserved */
	badaddr = 12,
	config,
	mpubase,
	mpuacc,
};

/* status register fields */
#define NIOS2_STATUS_PIE_MASK		0x00000001
#define NIOS2_STATUS_U_MASK		0x00000002
#define NIOS2_STATUS_EH_MASK		0x00000004

/* exception register fields */
#define NIOS2_EXCEPTION_CAUSE_MASK	0x0000007C
#define NIOS2_EXCEPTION_CAUSE_OFF	2

/* exception causes */
#define NIOS2_EX_RESET			0
#define NIOS2_EX_PROC_ONLY_RESET	1
#define NIOS2_EX_IRQ			2
#define NIOS2_EX_TRAP			3
#define NIOS2_EX_UNIMPLEMENTED		4
#define NIOS2_EX_DIV_ERR		8
#define NIOS2_EX_SUPERVISOR_ONLY_I	9
#define NIOS2_EX_SUPERVISOR_ONLY_D	11
#define NIOS2_EX_FAST_TLB_MISS		12

#define NIOS2_EX_NONE			255

/* pteaddr register fields */
#define NIOS2_PTEADDR_VPN_SHIFT		2
#define NIOS2_PTEADDR_VPN_MASK		0x007FFFFC
#define NIOS2_PTEADDR_PTBASE_SHIFT	22
#define NIOS2_PTEADDR_PTBASE_MASK	0xFFC00000

/* tlbacc register fields */
#define NIOS2_TLBACC_PFN_MASK	0x000FFFFF
#define NIOS2_TLBACC_G_MASK	0x00100000
#define NIOS2_TLBACC_X_MASK	0x00200000
#define NIOS2_TLBACC_W_MASK	0x00400000
#define NIOS2_TLBACC_R_MASK	0x00800000
#define NIOS2_TLBACC_C_MASK	0x01000000

/* tlbmisc register fields */
#define NIOS2_TLBMISC_D_MASK	0x00000001
#define NIOS2_TLBMISC_PERM_MASK	0x00000002
#define NIOS2_TLBMISC_BAD_MASK	0x00000004
#define NIOS2_TLBMISC_DBL_MASK	0x00000008
#define NIOS2_TLBMISC_PID_MASK	0x0007FFF0
#define NIOS2_TLBMISC_PID_OFF	4
#define NIOS2_TLBMISC_WE_MASK	0x00040000
#define NIOS2_TLBMISC_RD_MASK	0x00080000
#define NIOS2_TLBMISC_WAY_MASK	0x0007FFF0
#define NIOS2_TLBMISC_WAY_OFF	20

/* MMU-specific stuff */

#define TLB_NUM_ENTRIES	256
#define TLB_NUM_WAYS	16
#define TLB_NUM_LINES	(TLB_NUM_ENTRIES / TLB_NUM_WAYS)

struct tlb_entry {
	/* TLB Tag Portion */
	uint32_t vpn;
	uint16_t pid;
	uint8_t g;

	/* TLB Data Portion Contents */
	uint32_t pfn;
	uint8_t c;
	uint8_t r;
	uint8_t w;
	uint8_t x;

	/* TLB Data */
	uint32_t buffer;
};

extern void nios2_cpu_reset(struct nios2 *cpu);
extern void nios2_cpu_init(struct nios2 *cpu);
extern void nios2_simulate(struct nios2 *cpu);
extern void nios2_cpu_inc_pc(struct nios2 *cpu);
extern bool nios2_in_user_mode(struct nios2 *cpu);
extern bool nios2_in_supervisor_mode(struct nios2 *cpu);
extern void nios2_handle_exception(struct nios2 *cpu);
extern uint32_t nios2_fetch_instr(struct nios2 *cpu);
extern int nios2_execute_instr(struct nios2 *cpu, uint32_t instr);

extern int nios2_load(struct nios2 *cpu, uint32_t addr, void *data, size_t size);
extern int nios2_store(struct nios2 *cpu, uint32_t addr, void *data, size_t size);

extern void nios2_dump_registers(struct nios2 *cpu);

#endif /* _NIOS2_H_ */