/*
 * Copyright © 2009 Keith Packard <keithp@keithp.com>
 *
 * 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; version 2 of the License.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 */

#include "ao.h"
#include "25lc1024.h"

#define EE_BLOCK_SIZE	((uint16_t) (256))
#define EE_BLOCK_SHIFT	8
#define EE_DEVICE_SIZE	((uint32_t) 128 * (uint32_t) 1024)

/* Total bytes of available storage */
__pdata uint32_t	ao_storage_total;

/* Block size - device is erased in these units. At least 256 bytes */
__pdata uint32_t	ao_storage_block;

/* Byte offset of config block. Will be ao_storage_block bytes long */
__pdata uint32_t	ao_storage_config;

/* Storage unit size - device reads and writes must be within blocks of this size. Usually 256 bytes. */
__pdata uint16_t	ao_storage_unit;

/*
 * Using SPI on USART 0, with P1_2 as the chip select
 */

#define EE_CS		P1_2
#define EE_CS_INDEX	2

static __xdata uint8_t ao_ee_mutex;

#define ao_ee_delay() do { \
	_asm nop _endasm; \
	_asm nop _endasm; \
	_asm nop _endasm; \
} while(0)

static void ao_ee_cs_low(void)
{
	ao_ee_delay();
	EE_CS = 0;
	ao_ee_delay();
}

static void ao_ee_cs_high(void)
{
	ao_ee_delay();
	EE_CS = 1;
	ao_ee_delay();
}

struct ao_ee_instruction {
	uint8_t	instruction;
	uint8_t	address[3];
} __xdata ao_ee_instruction;

static void
ao_ee_write_enable(void)
{
	ao_ee_cs_low();
	ao_ee_instruction.instruction = EE_WREN;
	ao_spi_send(&ao_ee_instruction, 1);
	ao_ee_cs_high();
}

static uint8_t
ao_ee_rdsr(void)
{
	ao_ee_cs_low();
	ao_ee_instruction.instruction = EE_RDSR;
	ao_spi_send(&ao_ee_instruction, 1);
	ao_spi_recv(&ao_ee_instruction, 1);
	ao_ee_cs_high();
	return ao_ee_instruction.instruction;
}

static void
ao_ee_wrsr(uint8_t status)
{
	ao_ee_cs_low();
	ao_ee_instruction.instruction = EE_WRSR;
	ao_ee_instruction.address[0] = status;
	ao_spi_send(&ao_ee_instruction, 2);
	ao_ee_cs_high();
}

#define EE_BLOCK_NONE	0xffff

static __xdata uint8_t ao_ee_data[EE_BLOCK_SIZE];
static __pdata uint16_t ao_ee_block = EE_BLOCK_NONE;
static __pdata uint8_t	ao_ee_block_dirty;

/* Write the current block to the EEPROM */
static void
ao_ee_write_block(void)
{
	uint8_t	status;

	status = ao_ee_rdsr();
	if (status & (EE_STATUS_BP0|EE_STATUS_BP1|EE_STATUS_WPEN)) {
		status &= ~(EE_STATUS_BP0|EE_STATUS_BP1|EE_STATUS_WPEN);
		ao_ee_wrsr(status);
	}
	ao_ee_write_enable();
	ao_ee_cs_low();
	ao_ee_instruction.instruction = EE_WRITE;
	ao_ee_instruction.address[0] = ao_ee_block >> 8;
	ao_ee_instruction.address[1] = ao_ee_block;
	ao_ee_instruction.address[2] = 0;
	ao_spi_send(&ao_ee_instruction, 4);
	ao_spi_send(ao_ee_data, EE_BLOCK_SIZE);
	ao_ee_cs_high();
	for (;;) {
		uint8_t	status = ao_ee_rdsr();
		if ((status & EE_STATUS_WIP) == 0)
			break;
	}
}

/* Read the current block from the EEPROM */
static void
ao_ee_read_block(void)
{
	ao_ee_cs_low();
	ao_ee_instruction.instruction = EE_READ;
	ao_ee_instruction.address[0] = ao_ee_block >> 8;
	ao_ee_instruction.address[1] = ao_ee_block;
	ao_ee_instruction.address[2] = 0;
	ao_spi_send(&ao_ee_instruction, 4);
	ao_spi_recv(ao_ee_data, EE_BLOCK_SIZE);
	ao_ee_cs_high();
}

static void
ao_ee_flush_internal(void)
{
	if (ao_ee_block_dirty) {
		ao_ee_write_block();
		ao_ee_block_dirty = 0;
	}
}

static void
ao_ee_fill(uint16_t block)
{
	if (block != ao_ee_block) {
		ao_ee_flush_internal();
		ao_ee_block = block;
		ao_ee_read_block();
	}
}

uint8_t
ao_storage_device_write(uint32_t pos, __xdata void *buf, uint16_t len) __reentrant
{
	uint16_t block = (uint16_t) (pos >> EE_BLOCK_SHIFT);

	/* Transfer the data */
	ao_mutex_get(&ao_ee_mutex); {
		if (len != EE_BLOCK_SIZE)
			ao_ee_fill(block);
		else {
			ao_ee_flush_internal();
			ao_ee_block = block;
		}
		memcpy(ao_ee_data + (uint16_t) (pos & 0xff), buf, len);
		ao_ee_block_dirty = 1;
	} ao_mutex_put(&ao_ee_mutex);
	return 1;
}

uint8_t
ao_storage_device_read(uint32_t pos, __xdata void *buf, uint16_t len) __reentrant
{
	uint16_t block = (uint16_t) (pos >> EE_BLOCK_SHIFT);

	/* Transfer the data */
	ao_mutex_get(&ao_ee_mutex); {
		ao_ee_fill(block);
		memcpy(buf, ao_ee_data + (uint16_t) (pos & 0xff), len);
	} ao_mutex_put(&ao_ee_mutex);
	return 1;
}

void
ao_storage_flush(void) __reentrant
{
	ao_mutex_get(&ao_ee_mutex); {
		ao_ee_flush_internal();
	} ao_mutex_put(&ao_ee_mutex);
}

uint8_t
ao_storage_erase(uint32_t pos) __reentrant
{
	ao_mutex_get(&ao_ee_mutex); {
		ao_ee_flush_internal();
		ao_ee_block = (uint16_t) (pos >> EE_BLOCK_SHIFT);
		memset(ao_ee_data, 0xff, EE_BLOCK_SIZE);
		ao_ee_block_dirty = 1;
	} ao_mutex_put(&ao_ee_mutex);
	return 1;
}

static void
ee_store(void) __reentrant
{
}

void
ao_storage_setup(void)
{
	if (ao_storage_total == 0) {
		ao_storage_total = EE_DEVICE_SIZE;
		ao_storage_block = EE_BLOCK_SIZE;
		ao_storage_config = EE_DEVICE_SIZE - EE_BLOCK_SIZE;
		ao_storage_unit = EE_BLOCK_SIZE;
	}
}

void
ao_storage_device_info(void) __reentrant
{
}

/*
 * To initialize the chip, set up the CS line and
 * the SPI interface
 */
void
ao_storage_device_init(void)
{
	/* set up CS */
	EE_CS = 1;
	P1DIR |= (1 << EE_CS_INDEX);
	P1SEL &= ~(1 << EE_CS_INDEX);
}