/*
 * Copyright (c) 2013 Juergen Beisert <kernel@pengutronix.de>, Pengutronix
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * 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 <common.h>
#include <init.h>
#include <driver.h>
#include <firmware.h>
#include <of_gpio.h>
#include <xfuncs.h>
#include <malloc.h>
#include <gpio.h>
#include <clock.h>
#include <spi/spi.h>

#include <fcntl.h>
#include <fs.h>

/*
 * Physical requirements:
 * - free GPIOs for the signals nCONFIG, CONFIGURE_DONE, nSTATUS (optionally
 *   for ARRIA 10)
 * - 32 bit / 8 bit (ARRIA 10) per word, LSB first capable SPI master
 *   (MOSI + clock)
 *
 * Example how to configure this driver via device tree
 *
 *	fpga@0 {
 *		compatible = "altr,fpga-passive-serial";
 *		nstat-gpios = <&gpio4 18 0>;
 *		confd-gpios = <&gpio4 19 0>;
 *		nconfig-gpios = <&gpio4 20 0>;
 *		spi-max-frequency = <10000000>;
 *		reg = <0>;
 *	};
 */

struct altera_ps_data {
	int status_wait_max_us;
	int t_st2ck_us;
	int spi_bits_per_word;
	int padding;
};

struct fpga_spi {
	struct firmware_handler fh;
	int nstat_gpio; /* input GPIO to read the status line */
	int confd_gpio; /* input GPIO to read the config done line */
	int nconfig_gpio; /* output GPIO to start the FPGA's config */
	struct device_d *dev;
	struct spi_device *spi;
	const struct altera_ps_data *data;
	bool padding_done;
};

/*          |   Arria 5   |   Arria 10  |
 * t_CF2ST0 |     [; 600] |     [; 600] | ns
 * t_CFG    |        [2;] |        [2;] | µs
 * t_STATUS | [268; 1506] | [268; 3000] | µs
 * t_CF2ST1 |    [; 1506] |    [; 3000] | µs
 * t_CF2CK  |     [1506;] |  [3010 µs;] | µs
 * t_ST2CK  |        [2;] |       [10;] | µs
 * t_CD2UM  |  [175; 437] |  [175; 830] | µs
 */

/* Arria 5 */
static struct altera_ps_data a5_data = {
	.status_wait_max_us = 1506, /* max(t_CF2ST1) */
	.t_st2ck_us = 2, /* min(t_ST2CK) */
	.spi_bits_per_word = 32,
	.padding = true,
};

/* Arria 10 */
static struct altera_ps_data a10_data = {
	.status_wait_max_us = 3000, /* max(t_CF2ST1) */
	.t_st2ck_us = 10, /* min(t_ST2CK) */
	.spi_bits_per_word = 8,
	.padding = false,
};

static int altera_spi_open(struct firmware_handler *fh)
{
	struct fpga_spi *this = container_of(fh, struct fpga_spi, fh);
	struct device_d *dev = this->dev;
	int ret;

	dev_dbg(dev, "Initiating programming\n");

	/* initiate an FPGA programming */
	gpio_set_value(this->nconfig_gpio, 0);

	/*
	 * after about 2 µs the FPGA must acknowledge with
	 * STATUS and CONFIG DONE lines at low level
	 */
	if (gpio_is_valid(this->nstat_gpio)) {
		ret = wait_on_timeout(2 * USECOND,
				(gpio_get_value(this->nstat_gpio) == 0) &&
				(gpio_get_value(this->confd_gpio) == 0));
	} else {
		ret = wait_on_timeout(2 * USECOND,
				(gpio_get_value(this->confd_gpio) == 0));
	}

	if (ret != 0) {
		dev_err(dev, "FPGA does not acknowledge the programming initiation\n");
		if (gpio_is_valid(this->nstat_gpio) && gpio_get_value(this->nstat_gpio))
			dev_err(dev, "STATUS is still high!\n");
		if (gpio_get_value(this->confd_gpio))
			dev_err(dev, "CONFIG DONE is still high!\n");
		return ret;
	}

	/* arm the FPGA to await its new firmware */
	gpio_set_value(this->nconfig_gpio, 1);

	/* once again, we might need padding the data */
	this->padding_done = false;

	/*
	 * after max { max(t_STATUS), max(t_CF2ST1) } the FPGA must acknowledge this
	 * step with the STATUS line at high level
	 */
	if (gpio_is_valid(this->nstat_gpio)) {
		ret = wait_on_timeout(this->data->status_wait_max_us * USECOND,
				gpio_get_value(this->nstat_gpio));
		if (ret) {
			dev_err(dev, "nSTATUS still low after max(t_CF2ST1)! %d\n", ret);
			return ret;
		}
	} else {
		udelay(this->data->status_wait_max_us);
	}

	dev_dbg(dev, "Initiating passed\n");

	/*
	 * t_CF2CK doesn't need to be honored if nSTATUS is monitored in which
	 * case only t_ST2CK applies. As we have
	 * 	max(t_CF2ST1) + min(t_ST2CK) >= min(t_CF2CK)
	 * and we waited for max(t_CF2ST1) in the non-monitored
	 * case already above, only waiting for min(t_ST2CK) is fine here.
	 */
	udelay(this->data->t_st2ck_us * USECOND);

	return 0;
}

static int altera_spi_write(struct firmware_handler *fh, const void *buf, size_t sz)
{
	struct fpga_spi *this = container_of(fh, struct fpga_spi, fh);
	struct device_d *dev = this->dev;
	struct spi_transfer t[2];
	struct spi_message m;
	u32 dummy;
	int ret;

	dev_dbg(dev, "Start writing %zu bytes.\n", sz);

	spi_message_init(&m);

	if (this->data->padding) {
		if (sz < sizeof(u32)) {
			/* simple padding */
			dummy = 0;
			memcpy(&dummy, buf, sz);
			buf = &dummy;
			sz = sizeof(u32);
			this->padding_done = true;
		}

		t[0].tx_buf = buf;
		t[0].rx_buf = NULL;
		t[0].len = sz;
		spi_message_add_tail(&t[0], &m);

		if (sz & 0x3) { /* padding required? */
			u32 *word_buf = (u32 *)buf;
			dummy = 0;
			memcpy(&dummy, &word_buf[sz >> 2], sz & 0x3);
			t[0].len &= ~0x03;
			t[1].tx_buf = &dummy;
			t[1].rx_buf = NULL;
			t[1].len = sizeof(u32);
			spi_message_add_tail(&t[1], &m);
			this->padding_done = true;
		}
	} else {
		memset(&t[0], 0, sizeof(t[0]));
		t[0].tx_buf = buf;
		t[0].rx_buf = NULL;
		t[0].len = sz;
		spi_message_add_tail(&t[0], &m);
	}

	ret = spi_sync(this->spi, &m);
	if (ret != 0)
		dev_err(dev, "programming failure\n");

	return ret;
}

static int altera_spi_close(struct firmware_handler *fh)
{
	struct fpga_spi *this = container_of(fh, struct fpga_spi, fh);
	struct device_d *dev = this->dev;
	struct spi_transfer t;
	struct spi_message m;
	u32 dummy = 0;
	int ret;

	dev_dbg(dev, "Finalize programming\n");

	if (this->data->padding && this->padding_done == false) {
		spi_message_init(&m);
		t.tx_buf = &dummy;
		t.rx_buf = NULL;
		t.len = sizeof(dummy);
		spi_message_add_tail(&t, &m);

		ret = spi_sync(this->spi, &m);
		if (ret != 0)
			dev_err(dev, "programming failure\n");
	}

	/*
	 * when programming was successful,
	 * both status lines should be at high level
	 */
	if (gpio_is_valid(this->nstat_gpio)) {
		ret = wait_on_timeout(10 * USECOND,
				(gpio_get_value(this->nstat_gpio) == 1) &&
				(gpio_get_value(this->confd_gpio) == 1));
	} else {
		ret = wait_on_timeout(10 * USECOND,
				(gpio_get_value(this->confd_gpio) == 1));
	}


	if (ret == 0) {
		dev_dbg(dev, "Programming successful\n");

		/*
		 * After CONF_DONE goes high, send two additional falling edges on DCLK
		 * to begin initialization and enter user mode
		 */
		spi_message_init(&m);
		memset(&t, 0, sizeof(t));
		t.tx_buf = NULL;
		t.rx_buf = NULL;
		t.len = 2;
		spi_message_add_tail(&t, &m);
		return spi_sync(this->spi, &m);
	}

	dev_err(dev, "Programming failed due to time out\n");
	if (gpio_is_valid(this->nstat_gpio) &&
		gpio_get_value(this->nstat_gpio) == 0)
		dev_err(dev, "STATUS is still low!\n");
	if (gpio_get_value(this->confd_gpio) == 0)
		dev_err(dev, "CONFIG DONE is still low!\n");

	return -EIO;
}

static int altera_spi_of(struct device_d *dev, struct fpga_spi *this)
{
	struct device_node *n = dev->device_node;
	const char *name;
	int ret;

	name = "nstat-gpios";
	this->nstat_gpio = of_get_named_gpio(n, name, 0);
	if (this->nstat_gpio == -ENOENT) {
		dev_info(dev, "nstat-gpio is not specified, assuming it is not connected\n");
		this->nstat_gpio = -1;
	} else if (this->nstat_gpio < 0) {
		ret = this->nstat_gpio;
		goto out;
	}

	name = "confd-gpios";
	this->confd_gpio = of_get_named_gpio(n, name, 0);
	if (this->confd_gpio < 0) {
		ret = this->confd_gpio;
		goto out;
	}

	name = "nconfig-gpios";
	this->nconfig_gpio = of_get_named_gpio(n, name, 0);
	if (this->nconfig_gpio < 0) {
		ret = this->nconfig_gpio;
		goto out;
	}

	/* init to passive and sane values */
	ret = gpio_direction_output(this->nconfig_gpio, 1);
	if (ret)
		return ret;

	if (gpio_is_valid(this->nstat_gpio)) {
		ret = gpio_direction_input(this->nstat_gpio);
		if (ret)
			return ret;
	}

	ret = gpio_direction_input(this->confd_gpio);
	if (ret)
		return ret;

	return 0;

out:
	dev_err(dev, "Cannot request \"%s\" gpio: %s\n", name, strerror(-ret));

	return ret;
}

static void altera_spi_init_mode(struct spi_device *spi, int spi_bits_per_word)
{
	spi->bits_per_word = spi_bits_per_word;

	/*
	 * CPHA = CPOL = 0
	 * the FPGA expects its firmware data with LSB first
	 */
	spi->mode = SPI_MODE_0 | SPI_LSB_FIRST;
}

static int altera_spi_probe(struct device_d *dev)
{
	int rc;
	struct fpga_spi *this;
	struct firmware_handler *fh;
	const char *alias = of_alias_get(dev->device_node);
	const char *model = NULL;
	const struct altera_ps_data *data;

	dev_dbg(dev, "Probing FPGA firmware programmer\n");

	rc = dev_get_drvdata(dev, (const void **)&data);
	if (rc)
		return rc;

	this = xzalloc(sizeof(*this));
	fh = &this->fh;

	rc = altera_spi_of(dev, this);
	if (rc != 0)
		goto out;

	if (alias)
		fh->id = xstrdup(alias);
	else
		fh->id = xstrdup("altera-fpga");

	fh->open = altera_spi_open;
	fh->write = altera_spi_write;
	fh->close = altera_spi_close;
	of_property_read_string(dev->device_node, "compatible", &model);
	if (model)
		fh->model = xstrdup(model);
	fh->dev = dev;
	fh->device_node = dev->device_node;

	this->spi = (struct spi_device *)dev->type_data;
	this->data = data;

	altera_spi_init_mode(this->spi, this->data->spi_bits_per_word);
	this->dev = dev;

	dev_dbg(dev, "Registering FPGA firmware programmer\n");
	rc = firmwaremgr_register(fh);
	if (rc != 0) {
		free(this);
		goto out;
	}

	return 0;
out:
	free(fh->id);
	free(this);

	return rc;
}

static struct of_device_id altera_spi_id_table[] = {
	{ .compatible = "altr,fpga-passive-serial", .data = &a5_data },
	{ .compatible = "altr,fpga-arria10-passive-serial", .data = &a10_data },
	{ }
};

static struct driver_d altera_spi_driver = {
	.name = "altera-fpga",
	.of_compatible = DRV_OF_COMPAT(altera_spi_id_table),
	.probe = altera_spi_probe,
};
device_spi_driver(altera_spi_driver);
