/*
 *   OpenPSU firmware
 *   External UART control interface
 *
 *   Copyright (C) 2007 Michael Buesch <m@bues.ch>
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation; either version 2
 *   of the License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 */

#include "ext_control.h"
#include "calibration.h"
#include "util.h"
#include "main.h"

#include <avr/interrupt.h>
#include <stdint.h>


#define BAUDRATE	2400


/* The receive buffer. */
static uint8_t rx_buffer[sizeof(struct extctl_command)];
/* The number of bytes received. */
static uint8_t nr_rx_bytes;
/* Receive error flag */
static uint8_t rx_error;


static void usart_tx(uint8_t data)
{
	while (!(UCSR0A & (1 << UDRE0)))
		;
	UDR0 = data;
}

static void usart_tx_buffer(void *_buf, uint8_t size)
{
	uint8_t *buf = _buf;
	uint8_t i;

	for (i = 0; i < size; i++)
		usart_tx(buf[i]);
}

static int8_t usart_rx(uint8_t *data)
{
	uint8_t status;

	status = UCSR0A;
	if (!(status & (1 << RXC0)))
		return 1;
	*data = UDR0;
	if (unlikely(status & ((1 << FE0) | (1 << UPE0) | (1 << DOR0))))
		return -1;

	return 0;
}

static uint8_t crc8(uint8_t crc, uint8_t data)
{
	uint8_t i, tmp;

	for (i = 8; i > 0; i--) {
		tmp = ((crc ^ data) & 0x01);
		if (tmp) {
			crc ^= 0x18;
			crc >>= 1;
			crc |= 0x80;
		} else
			crc >>= 1;
		data >>= 1;
	}

	return crc;
}

/* Create an XOR checksum out of the buffer. */
static uint8_t checksum_buffer(const void *_buf, uint8_t size)
{
	uint8_t crc = 0;
	const uint8_t *buf = _buf;
	uint8_t i;

	for (i = 0; i < size; i++)
		crc = crc8(crc, buf[i]);
	crc ^= 0xFF;

	return crc;
}

static inline void command_result(uint8_t result_code)
{
	usart_tx(result_code);
}

static void send_command_reply(uint32_t data)
{
	struct extctl_reply reply;

	reply.data = cpu_to_le32(data);
	reply.checksum = checksum_buffer(&reply.data, sizeof(reply.data));
	usart_tx_buffer(&reply, sizeof(reply));
}

static void cmd_nop(uint32_t data)
{
	command_result(EXTCTL_CMD_RESULT_OK);
}

static void cmd_setvoltage(uint32_t data)
{
	uint16_t voltage;
	uint8_t profile;

	profile = (data & 0x00FF0000) >> 16;
	voltage = (data & 0x0000FFFF);
	if ((profile >= NR_PROFILES) ||
	    (voltage > MAX_VOLTAGE)) {
		command_result(EXTCTL_CMD_RESULT_EINVAL);
		return;
	}
	set_voltage_in_prof(profile, voltage);
	command_result(EXTCTL_CMD_RESULT_OK);
}

static void cmd_getvoltage(uint32_t data)
{
	uint8_t profile;
	uint16_t voltage;

	profile = (data & 0x00FF0000) >> 16;
	if (profile >= NR_PROFILES) {
		command_result(EXTCTL_CMD_RESULT_EINVAL);
		return;
	}
	command_result(EXTCTL_CMD_RESULT_OK);
	voltage = get_voltage_from_prof(profile);
	send_command_reply(voltage);
}

static void cmd_setmaxcur(uint32_t data)
{
	uint16_t maxcur;
	uint8_t profile;

	profile = (data & 0x00FF0000) >> 16;
	maxcur = (data & 0x0000FFFF);
	if ((profile >= NR_PROFILES) ||
	    (maxcur > MAX_CURRENT)) {
		command_result(EXTCTL_CMD_RESULT_EINVAL);
		return;
	}
	set_maxcur_in_prof(profile, maxcur);
	command_result(EXTCTL_CMD_RESULT_OK);
}

static void cmd_getmaxcur(uint32_t data)
{
	uint8_t profile;
	uint16_t maxcur;

	profile = (data & 0x00FF0000) >> 16;
	if (profile >= NR_PROFILES) {
		command_result(EXTCTL_CMD_RESULT_EINVAL);
		return;
	}
	command_result(EXTCTL_CMD_RESULT_OK);
	maxcur = get_maxcur_from_prof(profile);
	send_command_reply(maxcur);
}

static void cmd_switchprof(uint32_t data)
{
	uint8_t profile;

	profile = (data & 0x00FF0000) >> 16;
	if (profile >= NR_PROFILES) {
		command_result(EXTCTL_CMD_RESULT_EINVAL);
		return;
	}
	switch_to_profile(profile);
	command_result(EXTCTL_CMD_RESULT_OK);
}

static void cmd_getprof(uint32_t data)
{
	uint8_t profile;

	command_result(EXTCTL_CMD_RESULT_OK);
	profile = get_active_profile();
	send_command_reply((uint32_t)profile << 16);
}

/* We received a complete command. Handle it. */
static void handle_received_command(void)
{
	struct extctl_command *cmd = (struct extctl_command *)rx_buffer;
	uint32_t data;
	uint8_t checksum;

	checksum = checksum_buffer(rx_buffer,
				   sizeof(struct extctl_command) -
				   sizeof(uint8_t));
	if (unlikely(rx_error || cmd->checksum != checksum)) {
		/* Checksum error. */
		command_result(EXTCTL_CMD_RESULT_ECSUM);
		rx_error = 0;
		return;
	}
	data = le32_to_cpu(cmd->data);
	switch (cmd->id) {
	case EXTCTL_CMD_NOP:
		cmd_nop(data);
		break;
	case EXTCTL_CMD_SETVOLTAGE:
		cmd_setvoltage(data);
		break;
	case EXTCTL_CMD_GETVOLTAGE:
		cmd_getvoltage(data);
		break;
	case EXTCTL_CMD_SETMAXCUR:
		cmd_setmaxcur(data);
		break;
	case EXTCTL_CMD_GETMAXCUR:
		cmd_getmaxcur(data);
		break;
	case EXTCTL_CMD_SWITCHPROF:
		cmd_switchprof(data);
		break;
	case EXTCTL_CMD_GETPROF:
		cmd_getprof(data);
		break;
	default:
		command_result(EXTCTL_CMD_RESULT_EINVAL);
		return;
	}
}

ISR(USART_RX_vect)
{
	uint8_t data;
	int8_t err;

	while (1) {
		err = usart_rx(&data);
		if (err > 0)
			break;
		if (err)
			rx_error = 1;
		rx_buffer[nr_rx_bytes++] = data;
		if (nr_rx_bytes == sizeof(struct extctl_command)) {
			nr_rx_bytes = 0;
			handle_received_command();
		}
	}
}

static void usart_init(void)
{
	uint8_t dummy;

	/* Set baud rate */
	UBRR0 = (F_CPU / 16 / BAUDRATE);
	/* 8 Data bits, 1 Stop bit, Even parity */
	UCSR0C = (1 << UCSZ00) | (1 << UCSZ01) | (1 << UPM01);
	/* Enable transceiver and RX IRQs */
	UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
	/* Drain the RX buffer */
	while (usart_rx(&dummy) == 0)
		mb();
}

void extctl_init(void)
{
	nr_rx_bytes = 0;
	rx_error = 0;
	mb();
	usart_init();
}