drivers/nfc/st21nfca/i2c.c - third_party/linux - Git at Google

 /*
  * I2C Link Layer for ST21NFCA HCI based Driver
  * Copyright (C) 2014  STMicroelectronics SAS. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions 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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/crc-ccitt.h>
 #include <linux/module.h>
 #include <linux/i2c.h>
 #include <linux/gpio/consumer.h>
 #include <linux/of_irq.h>
 #include <linux/of_gpio.h>
 #include <linux/acpi.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/nfc.h>
 #include <linux/firmware.h>

 #include <asm/unaligned.h>

 #include <net/nfc/hci.h>
 #include <net/nfc/llc.h>
 #include <net/nfc/nfc.h>

 #include "st21nfca.h"

 /*
  * Every frame starts with ST21NFCA_SOF_EOF and ends with ST21NFCA_SOF_EOF.
  * Because ST21NFCA_SOF_EOF is a possible data value, there is a mecanism
  * called byte stuffing has been introduced.
  *
  * if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
  * - insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
  * - xor byte with ST21NFCA_BYTE_STUFFING_MASK
  */
 #define ST21NFCA_SOF_EOF		0x7e
 #define ST21NFCA_BYTE_STUFFING_MASK	0x20
 #define ST21NFCA_ESCAPE_BYTE_STUFFING	0x7d

 /* SOF + 00 */
 #define ST21NFCA_FRAME_HEADROOM			2

 /* 2 bytes crc + EOF */
 #define ST21NFCA_FRAME_TAILROOM 3
 #define IS_START_OF_FRAME(buf) (buf[0] == ST21NFCA_SOF_EOF && \
 				buf[1] == 0)

 #define ST21NFCA_HCI_DRIVER_NAME "st21nfca_hci"
 #define ST21NFCA_HCI_I2C_DRIVER_NAME "st21nfca_hci_i2c"

 #define ST21NFCA_GPIO_NAME_EN "enable"

 struct st21nfca_i2c_phy {
 	struct i2c_client *i2c_dev;
 	struct nfc_hci_dev *hdev;

 	struct gpio_desc *gpiod_ena;
 	struct st21nfca_se_status se_status;

 	struct sk_buff *pending_skb;
 	int current_read_len;
 	/*
 	 * crc might have fail because i2c macro
 	 * is disable due to other interface activity
 	 */
 	int crc_trials;

 	int powered;
 	int run_mode;

 	/*
 	 * < 0 if hardware error occured (e.g. i2c err)
 	 * and prevents normal operation.
 	 */
 	int hard_fault;
 	struct mutex phy_lock;
 };

 static u8 len_seq[] = { 16, 24, 12, 29 };
 static u16 wait_tab[] = { 2, 3, 5, 15, 20, 40};

 #define I2C_DUMP_SKB(info, skb)					\
 do {								\
 	pr_debug("%s:\n", info);				\
 	print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET,	\
 		       16, 1, (skb)->data, (skb)->len, 0);	\
 } while (0)

 /*
  * In order to get the CLF in a known state we generate an internal reboot
  * using a proprietary command.
  * Once the reboot is completed, we expect to receive a ST21NFCA_SOF_EOF
  * fill buffer.
  */
 static int st21nfca_hci_platform_init(struct st21nfca_i2c_phy *phy)
 {
 	u16 wait_reboot[] = { 50, 300, 1000 };
 	char reboot_cmd[] = { 0x7E, 0x66, 0x48, 0xF6, 0x7E };
 	u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE];
 	int i, r = -1;

 	for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
 		r = i2c_master_send(phy->i2c_dev, reboot_cmd,
 				    sizeof(reboot_cmd));
 		if (r < 0)
 			msleep(wait_reboot[i]);
 	}
 	if (r < 0)
 		return r;

 	/* CLF is spending about 20ms to do an internal reboot */
 	msleep(20);
 	r = -1;
 	for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
 		r = i2c_master_recv(phy->i2c_dev, tmp,
 				    ST21NFCA_HCI_LLC_MAX_SIZE);
 		if (r < 0)
 			msleep(wait_reboot[i]);
 	}
 	if (r < 0)
 		return r;

 	for (i = 0; i < ST21NFCA_HCI_LLC_MAX_SIZE &&
 		tmp[i] == ST21NFCA_SOF_EOF; i++)
 		;

 	if (r != ST21NFCA_HCI_LLC_MAX_SIZE)
 		return -ENODEV;

 	usleep_range(1000, 1500);
 	return 0;
 }

 static int st21nfca_hci_i2c_enable(void *phy_id)
 {
 	struct st21nfca_i2c_phy *phy = phy_id;

 	gpiod_set_value(phy->gpiod_ena, 1);
 	phy->powered = 1;
 	phy->run_mode = ST21NFCA_HCI_MODE;

 	usleep_range(10000, 15000);

 	return 0;
 }

 static void st21nfca_hci_i2c_disable(void *phy_id)
 {
 	struct st21nfca_i2c_phy *phy = phy_id;

 	gpiod_set_value(phy->gpiod_ena, 0);

 	phy->powered = 0;
 }

 static void st21nfca_hci_add_len_crc(struct sk_buff *skb)
 {
 	u16 crc;
 	u8 tmp;

 	*(u8 *)skb_push(skb, 1) = 0;

 	crc = crc_ccitt(0xffff, skb->data, skb->len);
 	crc = ~crc;

 	tmp = crc & 0x00ff;
 	*(u8 *)skb_put(skb, 1) = tmp;

 	tmp = (crc >> 8) & 0x00ff;
 	*(u8 *)skb_put(skb, 1) = tmp;
 }

 static void st21nfca_hci_remove_len_crc(struct sk_buff *skb)
 {
 	skb_pull(skb, ST21NFCA_FRAME_HEADROOM);
 	skb_trim(skb, skb->len - ST21NFCA_FRAME_TAILROOM);
 }

 /*
  * Writing a frame must not return the number of written bytes.
  * It must return either zero for success, or <0 for error.
  * In addition, it must not alter the skb
  */
 static int st21nfca_hci_i2c_write(void *phy_id, struct sk_buff *skb)
 {
 	int r = -1, i, j;
 	struct st21nfca_i2c_phy *phy = phy_id;
 	struct i2c_client *client = phy->i2c_dev;
 	u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE * 2];

 	I2C_DUMP_SKB("st21nfca_hci_i2c_write", skb);

 	if (phy->hard_fault != 0)
 		return phy->hard_fault;

 	/*
 	 * Compute CRC before byte stuffing computation on frame
 	 * Note st21nfca_hci_add_len_crc is doing a byte stuffing
 	 * on its own value
 	 */
 	st21nfca_hci_add_len_crc(skb);

 	/* add ST21NFCA_SOF_EOF on tail */
 	*(u8 *)skb_put(skb, 1) = ST21NFCA_SOF_EOF;
 	/* add ST21NFCA_SOF_EOF on head */
 	*(u8 *)skb_push(skb, 1) = ST21NFCA_SOF_EOF;

 	/*
 	 * Compute byte stuffing
 	 * if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
 	 * insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
 	 * xor byte with ST21NFCA_BYTE_STUFFING_MASK
 	 */
 	tmp[0] = skb->data[0];
 	for (i = 1, j = 1; i < skb->len - 1; i++, j++) {
 		if (skb->data[i] == ST21NFCA_SOF_EOF
 		    || skb->data[i] == ST21NFCA_ESCAPE_BYTE_STUFFING) {
 			tmp[j] = ST21NFCA_ESCAPE_BYTE_STUFFING;
 			j++;
 			tmp[j] = skb->data[i] ^ ST21NFCA_BYTE_STUFFING_MASK;
 		} else {
 			tmp[j] = skb->data[i];
 		}
 	}
 	tmp[j] = skb->data[i];
 	j++;

 	/*
 	 * Manage sleep mode
 	 * Try 3 times to send data with delay between each
 	 */
 	mutex_lock(&phy->phy_lock);
 	for (i = 0; i < ARRAY_SIZE(wait_tab) && r < 0; i++) {
 		r = i2c_master_send(client, tmp, j);
 		if (r < 0)
 			msleep(wait_tab[i]);
 	}
 	mutex_unlock(&phy->phy_lock);

 	if (r >= 0) {
 		if (r != j)
 			r = -EREMOTEIO;
 		else
 			r = 0;
 	}

 	st21nfca_hci_remove_len_crc(skb);

 	return r;
 }

 static int get_frame_size(u8 *buf, int buflen)
 {
 	int len = 0;

 	if (buf[len + 1] == ST21NFCA_SOF_EOF)
 		return 0;

 	for (len = 1; len < buflen && buf[len] != ST21NFCA_SOF_EOF; len++)
 		;

 	return len;
 }

 static int check_crc(u8 *buf, int buflen)
 {
 	u16 crc;

 	crc = crc_ccitt(0xffff, buf, buflen - 2);
 	crc = ~crc;

 	if (buf[buflen - 2] != (crc & 0xff) || buf[buflen - 1] != (crc >> 8)) {
 		pr_err(ST21NFCA_HCI_DRIVER_NAME
 		       ": CRC error 0x%x != 0x%x 0x%x\n", crc, buf[buflen - 1],
 		       buf[buflen - 2]);

 		pr_info(DRIVER_DESC ": %s : BAD CRC\n", __func__);
 		print_hex_dump(KERN_DEBUG, "crc: ", DUMP_PREFIX_NONE,
 			       16, 2, buf, buflen, false);
 		return -EPERM;
 	}
 	return 0;
 }

 /*
  * Prepare received data for upper layer.
  * Received data include byte stuffing, crc and sof/eof
  * which is not usable by hci part.
  * returns:
  * frame size without sof/eof, header and byte stuffing
  * -EBADMSG : frame was incorrect and discarded
  */
 static int st21nfca_hci_i2c_repack(struct sk_buff *skb)
 {
 	int i, j, r, size;

 	if (skb->len < 1 || (skb->len > 1 && skb->data[1] != 0))
 		return -EBADMSG;

 	size = get_frame_size(skb->data, skb->len);
 	if (size > 0) {
 		skb_trim(skb, size);
 		/* remove ST21NFCA byte stuffing for upper layer */
 		for (i = 1, j = 0; i < skb->len; i++) {
 			if (skb->data[i + j] ==
 					(u8) ST21NFCA_ESCAPE_BYTE_STUFFING) {
 				skb->data[i] = skb->data[i + j + 1]
 						| ST21NFCA_BYTE_STUFFING_MASK;
 				i++;
 				j++;
 			}
 			skb->data[i] = skb->data[i + j];
 		}
 		/* remove byte stuffing useless byte */
 		skb_trim(skb, i - j);
 		/* remove ST21NFCA_SOF_EOF from head */
 		skb_pull(skb, 1);

 		r = check_crc(skb->data, skb->len);
 		if (r != 0) {
 			i = 0;
 			return -EBADMSG;
 		}

 		/* remove headbyte */
 		skb_pull(skb, 1);
 		/* remove crc. Byte Stuffing is already removed here */
 		skb_trim(skb, skb->len - 2);
 		return skb->len;
 	}
 	return 0;
 }

 /*
  * Reads an shdlc frame and returns it in a newly allocated sk_buff. Guarantees
  * that i2c bus will be flushed and that next read will start on a new frame.
  * returned skb contains only LLC header and payload.
  * returns:
  * frame size : if received frame is complete (find ST21NFCA_SOF_EOF at
  * end of read)
  * -EAGAIN : if received frame is incomplete (not find ST21NFCA_SOF_EOF
  * at end of read)
  * -EREMOTEIO : i2c read error (fatal)
  * -EBADMSG : frame was incorrect and discarded
  * (value returned from st21nfca_hci_i2c_repack)
  * -EIO : if no ST21NFCA_SOF_EOF is found after reaching
  * the read length end sequence
  */
 static int st21nfca_hci_i2c_read(struct st21nfca_i2c_phy *phy,
 				 struct sk_buff *skb)
 {
 	int r, i;
 	u8 len;
 	u8 buf[ST21NFCA_HCI_LLC_MAX_PAYLOAD];
 	struct i2c_client *client = phy->i2c_dev;

 	if (phy->current_read_len < ARRAY_SIZE(len_seq)) {
 		len = len_seq[phy->current_read_len];

 		/*
 		 * Add retry mecanism
 		 * Operation on I2C interface may fail in case of operation on
 		 * RF or SWP interface
 		 */
 		r = 0;
 		mutex_lock(&phy->phy_lock);
 		for (i = 0; i < ARRAY_SIZE(wait_tab) && r <= 0; i++) {
 			r = i2c_master_recv(client, buf, len);
 			if (r < 0)
 				msleep(wait_tab[i]);
 		}
 		mutex_unlock(&phy->phy_lock);

 		if (r != len) {
 			phy->current_read_len = 0;
 			return -EREMOTEIO;
 		}

 		/*
 		 * The first read sequence does not start with SOF.
 		 * Data is corrupeted so we drop it.
 		 */
 		if (!phy->current_read_len && !IS_START_OF_FRAME(buf)) {
 			skb_trim(skb, 0);
 			phy->current_read_len = 0;
 			return -EIO;
 		} else if (phy->current_read_len && IS_START_OF_FRAME(buf)) {
 			/*
 			 * Previous frame transmission was interrupted and
 			 * the frame got repeated.
 			 * Received frame start with ST21NFCA_SOF_EOF + 00.
 			 */
 			skb_trim(skb, 0);
 			phy->current_read_len = 0;
 		}

 		skb_put_data(skb, buf, len);

 		if (skb->data[skb->len - 1] == ST21NFCA_SOF_EOF) {
 			phy->current_read_len = 0;
 			return st21nfca_hci_i2c_repack(skb);
 		}
 		phy->current_read_len++;
 		return -EAGAIN;
 	}
 	return -EIO;
 }

 /*
  * Reads an shdlc frame from the chip. This is not as straightforward as it
  * seems. The frame format is data-crc, and corruption can occur anywhere
  * while transiting on i2c bus, such that we could read an invalid data.
  * The tricky case is when we read a corrupted data or crc. We must detect
  * this here in order to determine that data can be transmitted to the hci
  * core. This is the reason why we check the crc here.
  * The CLF will repeat a frame until we send a RR on that frame.
  *
  * On ST21NFCA, IRQ goes in idle when read starts. As no size information are
  * available in the incoming data, other IRQ might come. Every IRQ will trigger
  * a read sequence with different length and will fill the current frame.
  * The reception is complete once we reach a ST21NFCA_SOF_EOF.
  */
 static irqreturn_t st21nfca_hci_irq_thread_fn(int irq, void *phy_id)
 {
 	struct st21nfca_i2c_phy *phy = phy_id;
 	struct i2c_client *client;

 	int r;

 	if (!phy || irq != phy->i2c_dev->irq) {
 		WARN_ON_ONCE(1);
 		return IRQ_NONE;
 	}

 	client = phy->i2c_dev;
 	dev_dbg(&client->dev, "IRQ\n");

 	if (phy->hard_fault != 0)
 		return IRQ_HANDLED;

 	r = st21nfca_hci_i2c_read(phy, phy->pending_skb);
 	if (r == -EREMOTEIO) {
 		phy->hard_fault = r;

 		nfc_hci_recv_frame(phy->hdev, NULL);

 		return IRQ_HANDLED;
 	} else if (r == -EAGAIN || r == -EIO) {
 		return IRQ_HANDLED;
 	} else if (r == -EBADMSG && phy->crc_trials < ARRAY_SIZE(wait_tab)) {
 		/*
 		 * With ST21NFCA, only one interface (I2C, RF or SWP)
 		 * may be active at a time.
 		 * Having incorrect crc is usually due to i2c macrocell
 		 * deactivation in the middle of a transmission.
 		 * It may generate corrupted data on i2c.
 		 * We give sometime to get i2c back.
 		 * The complete frame will be repeated.
 		 */
 		msleep(wait_tab[phy->crc_trials]);
 		phy->crc_trials++;
 		phy->current_read_len = 0;
 		kfree_skb(phy->pending_skb);
 	} else if (r > 0) {
 		/*
 		 * We succeeded to read data from the CLF and
 		 * data is valid.
 		 * Reset counter.
 		 */
 		nfc_hci_recv_frame(phy->hdev, phy->pending_skb);
 		phy->crc_trials = 0;
 	} else {
 		kfree_skb(phy->pending_skb);
 	}

 	phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
 	if (phy->pending_skb == NULL) {
 		phy->hard_fault = -ENOMEM;
 		nfc_hci_recv_frame(phy->hdev, NULL);
 	}

 	return IRQ_HANDLED;
 }

 static struct nfc_phy_ops i2c_phy_ops = {
 	.write = st21nfca_hci_i2c_write,
 	.enable = st21nfca_hci_i2c_enable,
 	.disable = st21nfca_hci_i2c_disable,
 };

 static int st21nfca_hci_i2c_acpi_request_resources(struct i2c_client *client)
 {
 	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
 	struct device *dev = &client->dev;

 	/* Get EN GPIO from ACPI */
 	phy->gpiod_ena = devm_gpiod_get_index(dev, ST21NFCA_GPIO_NAME_EN, 1,
 					      GPIOD_OUT_LOW);
 	if (IS_ERR(phy->gpiod_ena)) {
 		nfc_err(dev, "Unable to get ENABLE GPIO\n");
 		return PTR_ERR(phy->gpiod_ena);
 	}

 	return 0;
 }

 static int st21nfca_hci_i2c_of_request_resources(struct i2c_client *client)
 {
 	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
 	struct device *dev = &client->dev;

 	/* Get GPIO from device tree */
 	phy->gpiod_ena = devm_gpiod_get_index(dev, ST21NFCA_GPIO_NAME_EN, 0,
 					      GPIOD_OUT_HIGH);
 	if (IS_ERR(phy->gpiod_ena)) {
 		nfc_err(dev, "Failed to request enable pin\n");
 		return PTR_ERR(phy->gpiod_ena);
 	}

 	return 0;
 }

 static int st21nfca_hci_i2c_probe(struct i2c_client *client,
 				  const struct i2c_device_id *id)
 {
 	struct st21nfca_i2c_phy *phy;
 	int r;

 	dev_dbg(&client->dev, "%s\n", __func__);
 	dev_dbg(&client->dev, "IRQ: %d\n", client->irq);

 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 		nfc_err(&client->dev, "Need I2C_FUNC_I2C\n");
 		return -ENODEV;
 	}

 	phy = devm_kzalloc(&client->dev, sizeof(struct st21nfca_i2c_phy),
 			   GFP_KERNEL);
 	if (!phy)
 		return -ENOMEM;

 	phy->i2c_dev = client;
 	phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
 	if (phy->pending_skb == NULL)
 		return -ENOMEM;

 	phy->current_read_len = 0;
 	phy->crc_trials = 0;
 	mutex_init(&phy->phy_lock);
 	i2c_set_clientdata(client, phy);

 	if (client->dev.of_node) {
 		r = st21nfca_hci_i2c_of_request_resources(client);
 		if (r) {
 			nfc_err(&client->dev, "No platform data\n");
 			return r;
 		}
 	} else if (ACPI_HANDLE(&client->dev)) {
 		r = st21nfca_hci_i2c_acpi_request_resources(client);
 		if (r) {
 			nfc_err(&client->dev, "Cannot get ACPI data\n");
 			return r;
 		}
 	} else {
 		nfc_err(&client->dev, "st21nfca platform resources not available\n");
 		return -ENODEV;
 	}

 	phy->se_status.is_ese_present =
 			device_property_read_bool(&client->dev, "ese-present");
 	phy->se_status.is_uicc_present =
 			device_property_read_bool(&client->dev, "uicc-present");

 	r = st21nfca_hci_platform_init(phy);
 	if (r < 0) {
 		nfc_err(&client->dev, "Unable to reboot st21nfca\n");
 		return r;
 	}

 	r = devm_request_threaded_irq(&client->dev, client->irq, NULL,
 				st21nfca_hci_irq_thread_fn,
 				IRQF_ONESHOT,
 				ST21NFCA_HCI_DRIVER_NAME, phy);
 	if (r < 0) {
 		nfc_err(&client->dev, "Unable to register IRQ handler\n");
 		return r;
 	}

 	return st21nfca_hci_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
 					ST21NFCA_FRAME_HEADROOM,
 					ST21NFCA_FRAME_TAILROOM,
 					ST21NFCA_HCI_LLC_MAX_PAYLOAD,
 					&phy->hdev,
 					&phy->se_status);
 }

 static int st21nfca_hci_i2c_remove(struct i2c_client *client)
 {
 	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);

 	dev_dbg(&client->dev, "%s\n", __func__);

 	st21nfca_hci_remove(phy->hdev);

 	if (phy->powered)
 		st21nfca_hci_i2c_disable(phy);

 	return 0;
 }

 static struct i2c_device_id st21nfca_hci_i2c_id_table[] = {
 	{ST21NFCA_HCI_DRIVER_NAME, 0},
 	{}
 };
 MODULE_DEVICE_TABLE(i2c, st21nfca_hci_i2c_id_table);

 static const struct acpi_device_id st21nfca_hci_i2c_acpi_match[] = {
 	{"SMO2100", 0},
 	{}
 };
 MODULE_DEVICE_TABLE(acpi, st21nfca_hci_i2c_acpi_match);

 static const struct of_device_id of_st21nfca_i2c_match[] = {
 	{ .compatible = "st,st21nfca-i2c", },
 	{ .compatible = "st,st21nfca_i2c", },
 	{}
 };
 MODULE_DEVICE_TABLE(of, of_st21nfca_i2c_match);

 static struct i2c_driver st21nfca_hci_i2c_driver = {
 	.driver = {
 		.name = ST21NFCA_HCI_I2C_DRIVER_NAME,
 		.of_match_table = of_match_ptr(of_st21nfca_i2c_match),
 		.acpi_match_table = ACPI_PTR(st21nfca_hci_i2c_acpi_match),
 	},
 	.probe = st21nfca_hci_i2c_probe,
 	.id_table = st21nfca_hci_i2c_id_table,
 	.remove = st21nfca_hci_i2c_remove,
 };
 module_i2c_driver(st21nfca_hci_i2c_driver);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION(DRIVER_DESC);
	/*
	* I2C Link Layer for ST21NFCA HCI based Driver
	* Copyright (C) 2014 STMicroelectronics SAS. All rights reserved.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms and conditions 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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, see <http://www.gnu.org/licenses/>.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/crc-ccitt.h>
	#include <linux/module.h>
	#include <linux/i2c.h>
	#include <linux/gpio/consumer.h>
	#include <linux/of_irq.h>
	#include <linux/of_gpio.h>
	#include <linux/acpi.h>
	#include <linux/interrupt.h>
	#include <linux/delay.h>
	#include <linux/nfc.h>
	#include <linux/firmware.h>

	#include <asm/unaligned.h>

	#include <net/nfc/hci.h>
	#include <net/nfc/llc.h>
	#include <net/nfc/nfc.h>

	#include "st21nfca.h"

	/*
	* Every frame starts with ST21NFCA_SOF_EOF and ends with ST21NFCA_SOF_EOF.
	* Because ST21NFCA_SOF_EOF is a possible data value, there is a mecanism
	* called byte stuffing has been introduced.
	*
	* if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
	* - insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
	* - xor byte with ST21NFCA_BYTE_STUFFING_MASK
	*/
	#define ST21NFCA_SOF_EOF 0x7e
	#define ST21NFCA_BYTE_STUFFING_MASK 0x20
	#define ST21NFCA_ESCAPE_BYTE_STUFFING 0x7d

	/* SOF + 00 */
	#define ST21NFCA_FRAME_HEADROOM 2

	/* 2 bytes crc + EOF */
	#define ST21NFCA_FRAME_TAILROOM 3
	#define IS_START_OF_FRAME(buf) (buf[0] == ST21NFCA_SOF_EOF && \
	buf[1] == 0)

	#define ST21NFCA_HCI_DRIVER_NAME "st21nfca_hci"
	#define ST21NFCA_HCI_I2C_DRIVER_NAME "st21nfca_hci_i2c"

	#define ST21NFCA_GPIO_NAME_EN "enable"

	struct st21nfca_i2c_phy {
	struct i2c_client *i2c_dev;
	struct nfc_hci_dev *hdev;

	struct gpio_desc *gpiod_ena;
	struct st21nfca_se_status se_status;

	struct sk_buff *pending_skb;
	int current_read_len;
	/*
	* crc might have fail because i2c macro
	* is disable due to other interface activity
	*/
	int crc_trials;

	int powered;
	int run_mode;

	/*
	* < 0 if hardware error occured (e.g. i2c err)
	* and prevents normal operation.
	*/
	int hard_fault;
	struct mutex phy_lock;
	};

	static u8 len_seq[] = { 16, 24, 12, 29 };
	static u16 wait_tab[] = { 2, 3, 5, 15, 20, 40};

	#define I2C_DUMP_SKB(info, skb) \
	do { \
	pr_debug("%s:\n", info); \
	print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET, \
	16, 1, (skb)->data, (skb)->len, 0); \
	} while (0)

	/*
	* In order to get the CLF in a known state we generate an internal reboot
	* using a proprietary command.
	* Once the reboot is completed, we expect to receive a ST21NFCA_SOF_EOF
	* fill buffer.
	*/
	static int st21nfca_hci_platform_init(struct st21nfca_i2c_phy *phy)
	{
	u16 wait_reboot[] = { 50, 300, 1000 };
	char reboot_cmd[] = { 0x7E, 0x66, 0x48, 0xF6, 0x7E };
	u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE];
	int i, r = -1;

	for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
	r = i2c_master_send(phy->i2c_dev, reboot_cmd,
	sizeof(reboot_cmd));
	if (r < 0)
	msleep(wait_reboot[i]);
	}
	if (r < 0)
	return r;

	/* CLF is spending about 20ms to do an internal reboot */
	msleep(20);
	r = -1;
	for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
	r = i2c_master_recv(phy->i2c_dev, tmp,
	ST21NFCA_HCI_LLC_MAX_SIZE);
	if (r < 0)
	msleep(wait_reboot[i]);
	}
	if (r < 0)
	return r;

	for (i = 0; i < ST21NFCA_HCI_LLC_MAX_SIZE &&
	tmp[i] == ST21NFCA_SOF_EOF; i++)
	;

	if (r != ST21NFCA_HCI_LLC_MAX_SIZE)
	return -ENODEV;

	usleep_range(1000, 1500);
	return 0;
	}

	static int st21nfca_hci_i2c_enable(void *phy_id)
	{
	struct st21nfca_i2c_phy *phy = phy_id;

	gpiod_set_value(phy->gpiod_ena, 1);
	phy->powered = 1;
	phy->run_mode = ST21NFCA_HCI_MODE;

	usleep_range(10000, 15000);

	return 0;
	}

	static void st21nfca_hci_i2c_disable(void *phy_id)
	{
	struct st21nfca_i2c_phy *phy = phy_id;

	gpiod_set_value(phy->gpiod_ena, 0);

	phy->powered = 0;
	}

	static void st21nfca_hci_add_len_crc(struct sk_buff *skb)
	{
	u16 crc;
	u8 tmp;

	(u8 )skb_push(skb, 1) = 0;

	crc = crc_ccitt(0xffff, skb->data, skb->len);
	crc = ~crc;

	tmp = crc & 0x00ff;
	(u8 )skb_put(skb, 1) = tmp;

	tmp = (crc >> 8) & 0x00ff;
	(u8 )skb_put(skb, 1) = tmp;
	}

	static void st21nfca_hci_remove_len_crc(struct sk_buff *skb)
	{
	skb_pull(skb, ST21NFCA_FRAME_HEADROOM);
	skb_trim(skb, skb->len - ST21NFCA_FRAME_TAILROOM);
	}

	/*
	* Writing a frame must not return the number of written bytes.
	* It must return either zero for success, or <0 for error.
	* In addition, it must not alter the skb
	*/
	static int st21nfca_hci_i2c_write(void phy_id, struct sk_buff skb)
	{
	int r = -1, i, j;
	struct st21nfca_i2c_phy *phy = phy_id;
	struct i2c_client *client = phy->i2c_dev;
	u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE * 2];

	I2C_DUMP_SKB("st21nfca_hci_i2c_write", skb);

	if (phy->hard_fault != 0)
	return phy->hard_fault;

	/*
	* Compute CRC before byte stuffing computation on frame
	* Note st21nfca_hci_add_len_crc is doing a byte stuffing
	* on its own value
	*/
	st21nfca_hci_add_len_crc(skb);

	/* add ST21NFCA_SOF_EOF on tail */
	(u8 )skb_put(skb, 1) = ST21NFCA_SOF_EOF;
	/* add ST21NFCA_SOF_EOF on head */
	(u8 )skb_push(skb, 1) = ST21NFCA_SOF_EOF;

	/*
	* Compute byte stuffing
	* if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
	* insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
	* xor byte with ST21NFCA_BYTE_STUFFING_MASK
	*/
	tmp[0] = skb->data[0];
	for (i = 1, j = 1; i < skb->len - 1; i++, j++) {
	if (skb->data[i] == ST21NFCA_SOF_EOF
	\|\| skb->data[i] == ST21NFCA_ESCAPE_BYTE_STUFFING) {
	tmp[j] = ST21NFCA_ESCAPE_BYTE_STUFFING;
	j++;
	tmp[j] = skb->data[i] ^ ST21NFCA_BYTE_STUFFING_MASK;
	} else {
	tmp[j] = skb->data[i];
	}
	}
	tmp[j] = skb->data[i];
	j++;

	/*
	* Manage sleep mode
	* Try 3 times to send data with delay between each
	*/
	mutex_lock(&phy->phy_lock);
	for (i = 0; i < ARRAY_SIZE(wait_tab) && r < 0; i++) {
	r = i2c_master_send(client, tmp, j);
	if (r < 0)
	msleep(wait_tab[i]);
	}
	mutex_unlock(&phy->phy_lock);

	if (r >= 0) {
	if (r != j)
	r = -EREMOTEIO;
	else
	r = 0;
	}

	st21nfca_hci_remove_len_crc(skb);

	return r;
	}

	static int get_frame_size(u8 *buf, int buflen)
	{
	int len = 0;

	if (buf[len + 1] == ST21NFCA_SOF_EOF)
	return 0;

	for (len = 1; len < buflen && buf[len] != ST21NFCA_SOF_EOF; len++)
	;

	return len;
	}

	static int check_crc(u8 *buf, int buflen)
	{
	u16 crc;

	crc = crc_ccitt(0xffff, buf, buflen - 2);
	crc = ~crc;

	if (buf[buflen - 2] != (crc & 0xff) \|\| buf[buflen - 1] != (crc >> 8)) {
	pr_err(ST21NFCA_HCI_DRIVER_NAME
	": CRC error 0x%x != 0x%x 0x%x\n", crc, buf[buflen - 1],
	buf[buflen - 2]);

	pr_info(DRIVER_DESC ": %s : BAD CRC\n", __func__);
	print_hex_dump(KERN_DEBUG, "crc: ", DUMP_PREFIX_NONE,
	16, 2, buf, buflen, false);
	return -EPERM;
	}
	return 0;
	}

	/*
	* Prepare received data for upper layer.
	* Received data include byte stuffing, crc and sof/eof
	* which is not usable by hci part.
	* returns:
	* frame size without sof/eof, header and byte stuffing
	* -EBADMSG : frame was incorrect and discarded
	*/
	static int st21nfca_hci_i2c_repack(struct sk_buff *skb)
	{
	int i, j, r, size;

	if (skb->len < 1 \|\| (skb->len > 1 && skb->data[1] != 0))
	return -EBADMSG;

	size = get_frame_size(skb->data, skb->len);
	if (size > 0) {
	skb_trim(skb, size);
	/* remove ST21NFCA byte stuffing for upper layer */
	for (i = 1, j = 0; i < skb->len; i++) {
	if (skb->data[i + j] ==
	(u8) ST21NFCA_ESCAPE_BYTE_STUFFING) {
	skb->data[i] = skb->data[i + j + 1]
	\| ST21NFCA_BYTE_STUFFING_MASK;
	i++;
	j++;
	}
	skb->data[i] = skb->data[i + j];
	}
	/* remove byte stuffing useless byte */
	skb_trim(skb, i - j);
	/* remove ST21NFCA_SOF_EOF from head */
	skb_pull(skb, 1);

	r = check_crc(skb->data, skb->len);
	if (r != 0) {
	i = 0;
	return -EBADMSG;
	}

	/* remove headbyte */
	skb_pull(skb, 1);
	/* remove crc. Byte Stuffing is already removed here */
	skb_trim(skb, skb->len - 2);
	return skb->len;
	}
	return 0;
	}

	/*
	* Reads an shdlc frame and returns it in a newly allocated sk_buff. Guarantees
	* that i2c bus will be flushed and that next read will start on a new frame.
	* returned skb contains only LLC header and payload.
	* returns:
	* frame size : if received frame is complete (find ST21NFCA_SOF_EOF at
	* end of read)
	* -EAGAIN : if received frame is incomplete (not find ST21NFCA_SOF_EOF
	* at end of read)
	* -EREMOTEIO : i2c read error (fatal)
	* -EBADMSG : frame was incorrect and discarded
	* (value returned from st21nfca_hci_i2c_repack)
	* -EIO : if no ST21NFCA_SOF_EOF is found after reaching
	* the read length end sequence
	*/
	static int st21nfca_hci_i2c_read(struct st21nfca_i2c_phy *phy,
	struct sk_buff *skb)
	{
	int r, i;
	u8 len;
	u8 buf[ST21NFCA_HCI_LLC_MAX_PAYLOAD];
	struct i2c_client *client = phy->i2c_dev;

	if (phy->current_read_len < ARRAY_SIZE(len_seq)) {
	len = len_seq[phy->current_read_len];

	/*
	* Add retry mecanism
	* Operation on I2C interface may fail in case of operation on
	* RF or SWP interface
	*/
	r = 0;
	mutex_lock(&phy->phy_lock);
	for (i = 0; i < ARRAY_SIZE(wait_tab) && r <= 0; i++) {
	r = i2c_master_recv(client, buf, len);
	if (r < 0)
	msleep(wait_tab[i]);
	}
	mutex_unlock(&phy->phy_lock);

	if (r != len) {
	phy->current_read_len = 0;
	return -EREMOTEIO;
	}

	/*
	* The first read sequence does not start with SOF.
	* Data is corrupeted so we drop it.
	*/
	if (!phy->current_read_len && !IS_START_OF_FRAME(buf)) {
	skb_trim(skb, 0);
	phy->current_read_len = 0;
	return -EIO;
	} else if (phy->current_read_len && IS_START_OF_FRAME(buf)) {
	/*
	* Previous frame transmission was interrupted and
	* the frame got repeated.
	* Received frame start with ST21NFCA_SOF_EOF + 00.
	*/
	skb_trim(skb, 0);
	phy->current_read_len = 0;
	}

	skb_put_data(skb, buf, len);

	if (skb->data[skb->len - 1] == ST21NFCA_SOF_EOF) {
	phy->current_read_len = 0;
	return st21nfca_hci_i2c_repack(skb);
	}
	phy->current_read_len++;
	return -EAGAIN;
	}
	return -EIO;
	}

	/*
	* Reads an shdlc frame from the chip. This is not as straightforward as it
	* seems. The frame format is data-crc, and corruption can occur anywhere
	* while transiting on i2c bus, such that we could read an invalid data.
	* The tricky case is when we read a corrupted data or crc. We must detect
	* this here in order to determine that data can be transmitted to the hci
	* core. This is the reason why we check the crc here.
	* The CLF will repeat a frame until we send a RR on that frame.
	*
	* On ST21NFCA, IRQ goes in idle when read starts. As no size information are
	* available in the incoming data, other IRQ might come. Every IRQ will trigger
	* a read sequence with different length and will fill the current frame.
	* The reception is complete once we reach a ST21NFCA_SOF_EOF.
	*/
	static irqreturn_t st21nfca_hci_irq_thread_fn(int irq, void *phy_id)
	{
	struct st21nfca_i2c_phy *phy = phy_id;
	struct i2c_client *client;

	int r;

	if (!phy \|\| irq != phy->i2c_dev->irq) {
	WARN_ON_ONCE(1);
	return IRQ_NONE;
	}

	client = phy->i2c_dev;
	dev_dbg(&client->dev, "IRQ\n");

	if (phy->hard_fault != 0)
	return IRQ_HANDLED;

	r = st21nfca_hci_i2c_read(phy, phy->pending_skb);
	if (r == -EREMOTEIO) {
	phy->hard_fault = r;

	nfc_hci_recv_frame(phy->hdev, NULL);

	return IRQ_HANDLED;
	} else if (r == -EAGAIN \|\| r == -EIO) {
	return IRQ_HANDLED;
	} else if (r == -EBADMSG && phy->crc_trials < ARRAY_SIZE(wait_tab)) {
	/*
	* With ST21NFCA, only one interface (I2C, RF or SWP)
	* may be active at a time.
	* Having incorrect crc is usually due to i2c macrocell
	* deactivation in the middle of a transmission.
	* It may generate corrupted data on i2c.
	* We give sometime to get i2c back.
	* The complete frame will be repeated.
	*/
	msleep(wait_tab[phy->crc_trials]);
	phy->crc_trials++;
	phy->current_read_len = 0;
	kfree_skb(phy->pending_skb);
	} else if (r > 0) {
	/*
	* We succeeded to read data from the CLF and
	* data is valid.
	* Reset counter.
	*/
	nfc_hci_recv_frame(phy->hdev, phy->pending_skb);
	phy->crc_trials = 0;
	} else {
	kfree_skb(phy->pending_skb);
	}

	phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
	if (phy->pending_skb == NULL) {
	phy->hard_fault = -ENOMEM;
	nfc_hci_recv_frame(phy->hdev, NULL);
	}

	return IRQ_HANDLED;
	}

	static struct nfc_phy_ops i2c_phy_ops = {
	.write = st21nfca_hci_i2c_write,
	.enable = st21nfca_hci_i2c_enable,
	.disable = st21nfca_hci_i2c_disable,
	};

	static int st21nfca_hci_i2c_acpi_request_resources(struct i2c_client *client)
	{
	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
	struct device *dev = &client->dev;

	/* Get EN GPIO from ACPI */
	phy->gpiod_ena = devm_gpiod_get_index(dev, ST21NFCA_GPIO_NAME_EN, 1,
	GPIOD_OUT_LOW);
	if (IS_ERR(phy->gpiod_ena)) {
	nfc_err(dev, "Unable to get ENABLE GPIO\n");
	return PTR_ERR(phy->gpiod_ena);
	}

	return 0;
	}

	static int st21nfca_hci_i2c_of_request_resources(struct i2c_client *client)
	{
	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
	struct device *dev = &client->dev;

	/* Get GPIO from device tree */
	phy->gpiod_ena = devm_gpiod_get_index(dev, ST21NFCA_GPIO_NAME_EN, 0,
	GPIOD_OUT_HIGH);
	if (IS_ERR(phy->gpiod_ena)) {
	nfc_err(dev, "Failed to request enable pin\n");
	return PTR_ERR(phy->gpiod_ena);
	}

	return 0;
	}

	static int st21nfca_hci_i2c_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct st21nfca_i2c_phy *phy;
	int r;

	dev_dbg(&client->dev, "%s\n", __func__);
	dev_dbg(&client->dev, "IRQ: %d\n", client->irq);

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
	nfc_err(&client->dev, "Need I2C_FUNC_I2C\n");
	return -ENODEV;
	}

	phy = devm_kzalloc(&client->dev, sizeof(struct st21nfca_i2c_phy),
	GFP_KERNEL);
	if (!phy)
	return -ENOMEM;

	phy->i2c_dev = client;
	phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
	if (phy->pending_skb == NULL)
	return -ENOMEM;

	phy->current_read_len = 0;
	phy->crc_trials = 0;
	mutex_init(&phy->phy_lock);
	i2c_set_clientdata(client, phy);

	if (client->dev.of_node) {
	r = st21nfca_hci_i2c_of_request_resources(client);
	if (r) {
	nfc_err(&client->dev, "No platform data\n");
	return r;
	}
	} else if (ACPI_HANDLE(&client->dev)) {
	r = st21nfca_hci_i2c_acpi_request_resources(client);
	if (r) {
	nfc_err(&client->dev, "Cannot get ACPI data\n");
	return r;
	}
	} else {
	nfc_err(&client->dev, "st21nfca platform resources not available\n");
	return -ENODEV;
	}

	phy->se_status.is_ese_present =
	device_property_read_bool(&client->dev, "ese-present");
	phy->se_status.is_uicc_present =
	device_property_read_bool(&client->dev, "uicc-present");

	r = st21nfca_hci_platform_init(phy);
	if (r < 0) {
	nfc_err(&client->dev, "Unable to reboot st21nfca\n");
	return r;
	}

	r = devm_request_threaded_irq(&client->dev, client->irq, NULL,
	st21nfca_hci_irq_thread_fn,
	IRQF_ONESHOT,
	ST21NFCA_HCI_DRIVER_NAME, phy);
	if (r < 0) {
	nfc_err(&client->dev, "Unable to register IRQ handler\n");
	return r;
	}

	return st21nfca_hci_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
	ST21NFCA_FRAME_HEADROOM,
	ST21NFCA_FRAME_TAILROOM,
	ST21NFCA_HCI_LLC_MAX_PAYLOAD,
	&phy->hdev,
	&phy->se_status);
	}

	static int st21nfca_hci_i2c_remove(struct i2c_client *client)
	{
	struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);

	dev_dbg(&client->dev, "%s\n", __func__);

	st21nfca_hci_remove(phy->hdev);

	if (phy->powered)
	st21nfca_hci_i2c_disable(phy);

	return 0;
	}

	static struct i2c_device_id st21nfca_hci_i2c_id_table[] = {
	{ST21NFCA_HCI_DRIVER_NAME, 0},
	{}
	};
	MODULE_DEVICE_TABLE(i2c, st21nfca_hci_i2c_id_table);

	static const struct acpi_device_id st21nfca_hci_i2c_acpi_match[] = {
	{"SMO2100", 0},
	{}
	};
	MODULE_DEVICE_TABLE(acpi, st21nfca_hci_i2c_acpi_match);

	static const struct of_device_id of_st21nfca_i2c_match[] = {
	{ .compatible = "st,st21nfca-i2c", },
	{ .compatible = "st,st21nfca_i2c", },
	{}
	};
	MODULE_DEVICE_TABLE(of, of_st21nfca_i2c_match);

	static struct i2c_driver st21nfca_hci_i2c_driver = {
	.driver = {
	.name = ST21NFCA_HCI_I2C_DRIVER_NAME,
	.of_match_table = of_match_ptr(of_st21nfca_i2c_match),
	.acpi_match_table = ACPI_PTR(st21nfca_hci_i2c_acpi_match),
	},
	.probe = st21nfca_hci_i2c_probe,
	.id_table = st21nfca_hci_i2c_id_table,
	.remove = st21nfca_hci_i2c_remove,
	};
	module_i2c_driver(st21nfca_hci_i2c_driver);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION(DRIVER_DESC);