drivers/mfd/cros_ec_spi.c - kernel/bruno - Git at Google

 /*
  * ChromeOS EC multi-function device (SPI)
  *
  * Copyright (C) 2012 Google, Inc
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
  * may be copied, distributed, and modified under those terms.
  *
  * 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 <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mfd/cros_ec.h>
 #include <linux/mfd/cros_ec_commands.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/spi/spi.h>


 /* The header byte, which follows the preamble */
 #define EC_MSG_HEADER			0xec

 /*
  * Number of EC preamble bytes we read at a time. Since it takes
  * about 400-500us for the EC to respond there is not a lot of
  * point in tuning this. If the EC could respond faster then
  * we could increase this so that might expect the preamble and
  * message to occur in a single transaction. However, the maximum
  * SPI transfer size is 256 bytes, so at 5MHz we need a response
  * time of perhaps <320us (200 bytes / 1600 bits).
  */
 #define EC_MSG_PREAMBLE_COUNT		32

 /*
  * Allow for a long time for the EC to respond.  We support i2c
  * tunneling and support fairly long messages for the tunnel (249
  * bytes long at the moment).  If we're talking to a 100 kHz device
  * on the other end and need to transfer ~256 bytes, then we need:
  *  10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms
  *
  * We'll wait 4 times that to handle clock stretching and other
  * paranoia.
  *
  * It's pretty unlikely that we'll really see a 249 byte tunnel in
  * anything other than testing.  If this was more common we might
  * consider having slow commands like this require a GET_STATUS
  * wait loop.  The 'flash write' command would be another candidate
  * for this, clocking in at 2-3ms.
  */
 #define EC_MSG_DEADLINE_MS		100

 /*
   * Time between raising the SPI chip select (for the end of a
   * transaction) and dropping it again (for the next transaction).
   * If we go too fast, the EC will miss the transaction. We know that we
   * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
   * safe.
   */
 #define EC_SPI_RECOVERY_TIME_NS	(200 * 1000)

 /**
  * struct cros_ec_spi - information about a SPI-connected EC
  *
  * @spi: SPI device we are connected to
  * @last_transfer_ns: time that we last finished a transfer, or 0 if there
  *	if no record
  * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  *      is sent when we want to turn on CS at the start of a transaction.
  * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  *      is sent when we want to turn off CS at the end of a transaction.
  */
 struct cros_ec_spi {
 	struct spi_device *spi;
 	s64 last_transfer_ns;
 	unsigned int start_of_msg_delay;
 	unsigned int end_of_msg_delay;
 };

 static void debug_packet(struct device *dev, const char *name, u8 *ptr,
 			 int len)
 {
 #ifdef DEBUG
 	int i;

 	dev_dbg(dev, "%s: ", name);
 	for (i = 0; i < len; i++)
 		pr_cont(" %02x", ptr[i]);

 	pr_cont("\n");
 #endif
 }

 static int terminate_request(struct cros_ec_device *ec_dev)
 {
 	struct cros_ec_spi *ec_spi = ec_dev->priv;
 	struct spi_message msg;
 	struct spi_transfer trans;
 	int ret;

 	/*
 	 * Turn off CS, possibly adding a delay to ensure the rising edge
 	 * doesn't come too soon after the end of the data.
 	 */
 	spi_message_init(&msg);
 	memset(&trans, 0, sizeof(trans));
 	trans.delay_usecs = ec_spi->end_of_msg_delay;
 	spi_message_add_tail(&trans, &msg);

 	ret = spi_sync(ec_spi->spi, &msg);

 	/* Reset end-of-response timer */
 	ec_spi->last_transfer_ns = ktime_get_ns();
 	if (ret < 0) {
 		dev_err(ec_dev->dev,
 			"cs-deassert spi transfer failed: %d\n",
 			ret);
 	}

 	return ret;
 }

 /**
  * receive_n_bytes - receive n bytes from the EC.
  *
  * Assumes buf is a pointer into the ec_dev->din buffer
  */
 static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
 {
 	struct cros_ec_spi *ec_spi = ec_dev->priv;
 	struct spi_transfer trans;
 	struct spi_message msg;
 	int ret;

 	BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);

 	memset(&trans, 0, sizeof(trans));
 	trans.cs_change = 1;
 	trans.rx_buf = buf;
 	trans.len = n;

 	spi_message_init(&msg);
 	spi_message_add_tail(&trans, &msg);
 	ret = spi_sync(ec_spi->spi, &msg);
 	if (ret < 0)
 		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);

 	return ret;
 }

 /**
  * cros_ec_spi_receive_packet - Receive a packet from the EC.
  *
  * This function has two phases: reading the preamble bytes (since if we read
  * data from the EC before it is ready to send, we just get preamble) and
  * reading the actual message.
  *
  * The received data is placed into ec_dev->din.
  *
  * @ec_dev: ChromeOS EC device
  * @need_len: Number of message bytes we need to read
  */
 static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
 				      int need_len)
 {
 	struct ec_host_response *response;
 	u8 *ptr, *end;
 	int ret;
 	unsigned long deadline;
 	int todo;

 	BUG_ON(EC_MSG_PREAMBLE_COUNT > ec_dev->din_size);

 	/* Receive data until we see the header byte */
 	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
 	while (true) {
 		unsigned long start_jiffies = jiffies;

 		ret = receive_n_bytes(ec_dev,
 				      ec_dev->din,
 				      EC_MSG_PREAMBLE_COUNT);
 		if (ret < 0)
 			return ret;

 		ptr = ec_dev->din;
 		for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
 			if (*ptr == EC_SPI_FRAME_START) {
 				dev_dbg(ec_dev->dev, "msg found at %zd\n",
 					ptr - ec_dev->din);
 				break;
 			}
 		}
 		if (ptr != end)
 			break;

 		/*
 		 * Use the time at the start of the loop as a timeout.  This
 		 * gives us one last shot at getting the transfer and is useful
 		 * in case we got context switched out for a while.
 		 */
 		if (time_after(start_jiffies, deadline)) {
 			dev_warn(ec_dev->dev, "EC failed to respond in time\n");
 			return -ETIMEDOUT;
 		}
 	}

 	/*
 	 * ptr now points to the header byte. Copy any valid data to the
 	 * start of our buffer
 	 */
 	todo = end - ++ptr;
 	BUG_ON(todo < 0 || todo > ec_dev->din_size);
 	todo = min(todo, need_len);
 	memmove(ec_dev->din, ptr, todo);
 	ptr = ec_dev->din + todo;
 	dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
 		need_len, todo);
 	need_len -= todo;

 	/* If the entire response struct wasn't read, get the rest of it. */
 	if (todo < sizeof(*response)) {
 		ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo);
 		if (ret < 0)
 			return -EBADMSG;
 		ptr += (sizeof(*response) - todo);
 		todo = sizeof(*response);
 	}

 	response = (struct ec_host_response *)ec_dev->din;

 	/* Abort if data_len is too large. */
 	if (response->data_len > ec_dev->din_size)
 		return -EMSGSIZE;

 	/* Receive data until we have it all */
 	while (need_len > 0) {
 		/*
 		 * We can't support transfers larger than the SPI FIFO size
 		 * unless we have DMA. We don't have DMA on the ISP SPI ports
 		 * for Exynos. We need a way of asking SPI driver for
 		 * maximum-supported transfer size.
 		 */
 		todo = min(need_len, 256);
 		dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
 			todo, need_len, ptr - ec_dev->din);

 		ret = receive_n_bytes(ec_dev, ptr, todo);
 		if (ret < 0)
 			return ret;

 		ptr += todo;
 		need_len -= todo;
 	}

 	dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);

 	return 0;
 }

 /**
  * cros_ec_spi_receive_response - Receive a response from the EC.
  *
  * This function has two phases: reading the preamble bytes (since if we read
  * data from the EC before it is ready to send, we just get preamble) and
  * reading the actual message.
  *
  * The received data is placed into ec_dev->din.
  *
  * @ec_dev: ChromeOS EC device
  * @need_len: Number of message bytes we need to read
  */
 static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
 					int need_len)
 {
 	u8 *ptr, *end;
 	int ret;
 	unsigned long deadline;
 	int todo;

 	BUG_ON(EC_MSG_PREAMBLE_COUNT > ec_dev->din_size);

 	/* Receive data until we see the header byte */
 	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
 	while (true) {
 		unsigned long start_jiffies = jiffies;

 		ret = receive_n_bytes(ec_dev,
 				      ec_dev->din,
 				      EC_MSG_PREAMBLE_COUNT);
 		if (ret < 0)
 			return ret;

 		ptr = ec_dev->din;
 		for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
 			if (*ptr == EC_SPI_FRAME_START) {
 				dev_dbg(ec_dev->dev, "msg found at %zd\n",
 					ptr - ec_dev->din);
 				break;
 			}
 		}
 		if (ptr != end)
 			break;

 		/*
 		 * Use the time at the start of the loop as a timeout.  This
 		 * gives us one last shot at getting the transfer and is useful
 		 * in case we got context switched out for a while.
 		 */
 		if (time_after(start_jiffies, deadline)) {
 			dev_warn(ec_dev->dev, "EC failed to respond in time\n");
 			return -ETIMEDOUT;
 		}
 	}

 	/*
 	 * ptr now points to the header byte. Copy any valid data to the
 	 * start of our buffer
 	 */
 	todo = end - ++ptr;
 	BUG_ON(todo < 0 || todo > ec_dev->din_size);
 	todo = min(todo, need_len);
 	memmove(ec_dev->din, ptr, todo);
 	ptr = ec_dev->din + todo;
 	dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
 		 need_len, todo);
 	need_len -= todo;

 	/* Receive data until we have it all */
 	while (need_len > 0) {
 		/*
 		 * We can't support transfers larger than the SPI FIFO size
 		 * unless we have DMA. We don't have DMA on the ISP SPI ports
 		 * for Exynos. We need a way of asking SPI driver for
 		 * maximum-supported transfer size.
 		 */
 		todo = min(need_len, 256);
 		dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
 			todo, need_len, ptr - ec_dev->din);

 		ret = receive_n_bytes(ec_dev, ptr, todo);
 		if (ret < 0)
 			return ret;

 		debug_packet(ec_dev->dev, "interim", ptr, todo);
 		ptr += todo;
 		need_len -= todo;
 	}

 	dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);

 	return 0;
 }

 /**
  * cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
  *
  * @ec_dev: ChromeOS EC device
  * @ec_msg: Message to transfer
  */
 static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
 				struct cros_ec_command *ec_msg)
 {
 	struct ec_host_request *request;
 	struct ec_host_response *response;
 	struct cros_ec_spi *ec_spi = ec_dev->priv;
 	struct spi_transfer trans, trans_delay;
 	struct spi_message msg;
 	int i, len;
 	u8 *ptr;
 	u8 *rx_buf;
 	u8 sum;
 	int ret = 0, final_ret;

 	len = cros_ec_prepare_tx(ec_dev, ec_msg);
 	request = (struct ec_host_request *)ec_dev->dout;
 	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);

 	/* If it's too soon to do another transaction, wait */
 	if (ec_spi->last_transfer_ns) {
 		unsigned long delay;	/* The delay completed so far */

 		delay = ktime_get_ns() - ec_spi->last_transfer_ns;
 		if (delay < EC_SPI_RECOVERY_TIME_NS)
 			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 	}

 	rx_buf = kzalloc(len, GFP_KERNEL);
 	if (!rx_buf) {
 		ret = -ENOMEM;
 		goto exit;
 	}

 	/*
 	 * Leave a gap between CS assertion and clocking of data to allow the
 	 * EC time to wakeup.
 	 */
 	spi_message_init(&msg);
 	if (ec_spi->start_of_msg_delay) {
 		memset(&trans_delay, 0, sizeof(trans_delay));
 		trans_delay.delay_usecs = ec_spi->start_of_msg_delay;
 		spi_message_add_tail(&trans_delay, &msg);
 	}

 	/* Transmit phase - send our message */
 	memset(&trans, 0, sizeof(trans));
 	trans.tx_buf = ec_dev->dout;
 	trans.rx_buf = rx_buf;
 	trans.len = len;
 	trans.cs_change = 1;
 	spi_message_add_tail(&trans, &msg);
 	ret = spi_sync(ec_spi->spi, &msg);

 	/* Get the response */
 	if (!ret) {
 		/* Verify that EC can process command */
 		for (i = 0; i < len; i++) {
 			switch (rx_buf[i]) {
 			case EC_SPI_PAST_END:
 			case EC_SPI_RX_BAD_DATA:
 			case EC_SPI_NOT_READY:
 				ret = -EAGAIN;
 				ec_msg->result = EC_RES_IN_PROGRESS;
 			default:
 				break;
 			}
 			if (ret)
 				break;
 		}
 		if (!ret)
 			ret = cros_ec_spi_receive_packet(ec_dev,
 					ec_msg->insize + sizeof(*response));
 	} else {
 		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 	}

 	final_ret = terminate_request(ec_dev);
 	if (!ret)
 		ret = final_ret;
 	if (ret < 0)
 		goto exit;

 	ptr = ec_dev->din;

 	/* check response error code */
 	response = (struct ec_host_response *)ptr;
 	ec_msg->result = response->result;

 	ret = cros_ec_check_result(ec_dev, ec_msg);
 	if (ret)
 		goto exit;

 	len = response->data_len;
 	sum = 0;
 	if (len > ec_msg->insize) {
 		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
 			len, ec_msg->insize);
 		ret = -EMSGSIZE;
 		goto exit;
 	}

 	for (i = 0; i < sizeof(*response); i++)
 		sum += ptr[i];

 	/* copy response packet payload and compute checksum */
 	memcpy(ec_msg->data, ptr + sizeof(*response), len);
 	for (i = 0; i < len; i++)
 		sum += ec_msg->data[i];

 	if (sum) {
 		dev_err(ec_dev->dev,
 			"bad packet checksum, calculated %x\n",
 			sum);
 		ret = -EBADMSG;
 		goto exit;
 	}

 	ret = len;
 exit:
 	kfree(rx_buf);
 	if (ec_msg->command == EC_CMD_REBOOT_EC)
 		msleep(EC_REBOOT_DELAY_MS);

 	return ret;
 }

 /**
  * cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
  *
  * @ec_dev: ChromeOS EC device
  * @ec_msg: Message to transfer
  */
 static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
 				struct cros_ec_command *ec_msg)
 {
 	struct cros_ec_spi *ec_spi = ec_dev->priv;
 	struct spi_transfer trans;
 	struct spi_message msg;
 	int i, len;
 	u8 *ptr;
 	u8 *rx_buf;
 	int sum;
 	int ret = 0, final_ret;

 	len = cros_ec_prepare_tx(ec_dev, ec_msg);
 	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);

 	/* If it's too soon to do another transaction, wait */
 	if (ec_spi->last_transfer_ns) {
 		unsigned long delay;	/* The delay completed so far */

 		delay = ktime_get_ns() - ec_spi->last_transfer_ns;
 		if (delay < EC_SPI_RECOVERY_TIME_NS)
 			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 	}

 	rx_buf = kzalloc(len, GFP_KERNEL);
 	if (!rx_buf) {
 		ret = -ENOMEM;
 		goto exit;
 	}

 	/* Transmit phase - send our message */
 	debug_packet(ec_dev->dev, "out", ec_dev->dout, len);
 	memset(&trans, 0, sizeof(trans));
 	trans.tx_buf = ec_dev->dout;
 	trans.rx_buf = rx_buf;
 	trans.len = len;
 	trans.cs_change = 1;
 	spi_message_init(&msg);
 	spi_message_add_tail(&trans, &msg);
 	ret = spi_sync(ec_spi->spi, &msg);

 	/* Get the response */
 	if (!ret) {
 		/* Verify that EC can process command */
 		for (i = 0; i < len; i++) {
 			switch (rx_buf[i]) {
 			case EC_SPI_PAST_END:
 			case EC_SPI_RX_BAD_DATA:
 			case EC_SPI_NOT_READY:
 				ret = -EAGAIN;
 				ec_msg->result = EC_RES_IN_PROGRESS;
 			default:
 				break;
 			}
 			if (ret)
 				break;
 		}
 		if (!ret)
 			ret = cros_ec_spi_receive_response(ec_dev,
 					ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
 	} else {
 		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 	}

 	final_ret = terminate_request(ec_dev);
 	if (!ret)
 		ret = final_ret;
 	if (ret < 0)
 		goto exit;

 	ptr = ec_dev->din;

 	/* check response error code */
 	ec_msg->result = ptr[0];
 	ret = cros_ec_check_result(ec_dev, ec_msg);
 	if (ret)
 		goto exit;

 	len = ptr[1];
 	sum = ptr[0] + ptr[1];
 	if (len > ec_msg->insize) {
 		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
 			len, ec_msg->insize);
 		ret = -ENOSPC;
 		goto exit;
 	}

 	/* copy response packet payload and compute checksum */
 	for (i = 0; i < len; i++) {
 		sum += ptr[i + 2];
 		if (ec_msg->insize)
 			ec_msg->data[i] = ptr[i + 2];
 	}
 	sum &= 0xff;

 	debug_packet(ec_dev->dev, "in", ptr, len + 3);

 	if (sum != ptr[len + 2]) {
 		dev_err(ec_dev->dev,
 			"bad packet checksum, expected %02x, got %02x\n",
 			sum, ptr[len + 2]);
 		ret = -EBADMSG;
 		goto exit;
 	}

 	ret = len;
 exit:
 	kfree(rx_buf);
 	if (ec_msg->command == EC_CMD_REBOOT_EC)
 		msleep(EC_REBOOT_DELAY_MS);

 	return ret;
 }

 static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
 {
 	struct device_node *np = dev->of_node;
 	u32 val;
 	int ret;

 	ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
 	if (!ret)
 		ec_spi->start_of_msg_delay = val;

 	ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
 	if (!ret)
 		ec_spi->end_of_msg_delay = val;
 }

 static int cros_ec_spi_probe(struct spi_device *spi)
 {
 	struct device *dev = &spi->dev;
 	struct cros_ec_device *ec_dev;
 	struct cros_ec_spi *ec_spi;
 	int err;

 	spi->bits_per_word = 8;
 	spi->mode = SPI_MODE_0;
 	err = spi_setup(spi);
 	if (err < 0)
 		return err;

 	ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL);
 	if (ec_spi == NULL)
 		return -ENOMEM;
 	ec_spi->spi = spi;
 	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
 	if (!ec_dev)
 		return -ENOMEM;

 	/* Check for any DT properties */
 	cros_ec_spi_dt_probe(ec_spi, dev);

 	spi_set_drvdata(spi, ec_dev);
 	ec_dev->dev = dev;
 	ec_dev->priv = ec_spi;
 	ec_dev->irq = spi->irq;
 	ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
 	ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
 	ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
 	ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
 			   sizeof(struct ec_host_response) +
 			   sizeof(struct ec_response_get_protocol_info);
 	ec_dev->dout_size = sizeof(struct ec_host_request);


 	err = cros_ec_register(ec_dev);
 	if (err) {
 		dev_err(dev, "cannot register EC\n");
 		return err;
 	}

 	device_init_wakeup(&spi->dev, true);

 	return 0;
 }

 static int cros_ec_spi_remove(struct spi_device *spi)
 {
 	struct cros_ec_device *ec_dev;

 	ec_dev = spi_get_drvdata(spi);
 	cros_ec_remove(ec_dev);

 	return 0;
 }

 #ifdef CONFIG_PM_SLEEP
 static int cros_ec_spi_suspend(struct device *dev)
 {
 	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);

 	return cros_ec_suspend(ec_dev);
 }

 static int cros_ec_spi_resume(struct device *dev)
 {
 	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);

 	return cros_ec_resume(ec_dev);
 }
 #endif

 static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
 			 cros_ec_spi_resume);

 static const struct of_device_id cros_ec_spi_of_match[] = {
 	{ .compatible = "google,cros-ec-spi", },
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, cros_ec_spi_of_match);

 static const struct spi_device_id cros_ec_spi_id[] = {
 	{ "cros-ec-spi", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);

 static struct spi_driver cros_ec_driver_spi = {
 	.driver	= {
 		.name	= "cros-ec-spi",
 		.of_match_table = of_match_ptr(cros_ec_spi_of_match),
 		.pm	= &cros_ec_spi_pm_ops,
 	},
 	.probe		= cros_ec_spi_probe,
 	.remove		= cros_ec_spi_remove,
 	.id_table	= cros_ec_spi_id,
 };

 module_spi_driver(cros_ec_driver_spi);

 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)");
	/*
	* ChromeOS EC multi-function device (SPI)
	*
	* Copyright (C) 2012 Google, Inc
	*
	* This software is licensed under the terms of the GNU General Public
	* License version 2, as published by the Free Software Foundation, and
	* may be copied, distributed, and modified under those terms.
	*
	* 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 <linux/delay.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/mfd/cros_ec.h>
	#include <linux/mfd/cros_ec_commands.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/slab.h>
	#include <linux/spi/spi.h>


	/* The header byte, which follows the preamble */
	#define EC_MSG_HEADER 0xec

	/*
	* Number of EC preamble bytes we read at a time. Since it takes
	* about 400-500us for the EC to respond there is not a lot of
	* point in tuning this. If the EC could respond faster then
	* we could increase this so that might expect the preamble and
	* message to occur in a single transaction. However, the maximum
	* SPI transfer size is 256 bytes, so at 5MHz we need a response
	* time of perhaps <320us (200 bytes / 1600 bits).
	*/
	#define EC_MSG_PREAMBLE_COUNT 32

	/*
	* Allow for a long time for the EC to respond. We support i2c
	* tunneling and support fairly long messages for the tunnel (249
	* bytes long at the moment). If we're talking to a 100 kHz device
	* on the other end and need to transfer ~256 bytes, then we need:
	* 10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms
	*
	* We'll wait 4 times that to handle clock stretching and other
	* paranoia.
	*
	* It's pretty unlikely that we'll really see a 249 byte tunnel in
	* anything other than testing. If this was more common we might
	* consider having slow commands like this require a GET_STATUS
	* wait loop. The 'flash write' command would be another candidate
	* for this, clocking in at 2-3ms.
	*/
	#define EC_MSG_DEADLINE_MS 100

	/*
	* Time between raising the SPI chip select (for the end of a
	* transaction) and dropping it again (for the next transaction).
	* If we go too fast, the EC will miss the transaction. We know that we
	* need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
	* safe.
	*/
	#define EC_SPI_RECOVERY_TIME_NS (200 * 1000)

	/**
	* struct cros_ec_spi - information about a SPI-connected EC
	*
	* @spi: SPI device we are connected to
	* @last_transfer_ns: time that we last finished a transfer, or 0 if there
	* if no record
	* @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
	* is sent when we want to turn on CS at the start of a transaction.
	* @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
	* is sent when we want to turn off CS at the end of a transaction.
	*/
	struct cros_ec_spi {
	struct spi_device *spi;
	s64 last_transfer_ns;
	unsigned int start_of_msg_delay;
	unsigned int end_of_msg_delay;
	};

	static void debug_packet(struct device dev, const char name, u8 *ptr,
	int len)
	{
	#ifdef DEBUG
	int i;

	dev_dbg(dev, "%s: ", name);
	for (i = 0; i < len; i++)
	pr_cont(" %02x", ptr[i]);

	pr_cont("\n");
	#endif
	}

	static int terminate_request(struct cros_ec_device *ec_dev)
	{
	struct cros_ec_spi *ec_spi = ec_dev->priv;
	struct spi_message msg;
	struct spi_transfer trans;
	int ret;

	/*
	* Turn off CS, possibly adding a delay to ensure the rising edge
	* doesn't come too soon after the end of the data.
	*/
	spi_message_init(&msg);
	memset(&trans, 0, sizeof(trans));
	trans.delay_usecs = ec_spi->end_of_msg_delay;
	spi_message_add_tail(&trans, &msg);

	ret = spi_sync(ec_spi->spi, &msg);

	/* Reset end-of-response timer */
	ec_spi->last_transfer_ns = ktime_get_ns();
	if (ret < 0) {
	dev_err(ec_dev->dev,
	"cs-deassert spi transfer failed: %d\n",
	ret);
	}

	return ret;
	}

	/**
	* receive_n_bytes - receive n bytes from the EC.
	*
	* Assumes buf is a pointer into the ec_dev->din buffer
	*/
	static int receive_n_bytes(struct cros_ec_device ec_dev, u8 buf, int n)
	{
	struct cros_ec_spi *ec_spi = ec_dev->priv;
	struct spi_transfer trans;
	struct spi_message msg;
	int ret;

	BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);

	memset(&trans, 0, sizeof(trans));
	trans.cs_change = 1;
	trans.rx_buf = buf;
	trans.len = n;

	spi_message_init(&msg);
	spi_message_add_tail(&trans, &msg);
	ret = spi_sync(ec_spi->spi, &msg);
	if (ret < 0)
	dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);

	return ret;
	}

	/**
	* cros_ec_spi_receive_packet - Receive a packet from the EC.
	*
	* This function has two phases: reading the preamble bytes (since if we read
	* data from the EC before it is ready to send, we just get preamble) and
	* reading the actual message.
	*
	* The received data is placed into ec_dev->din.
	*
	* @ec_dev: ChromeOS EC device
	* @need_len: Number of message bytes we need to read
	*/
	static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
	int need_len)
	{
	struct ec_host_response *response;
	u8 ptr, end;
	int ret;
	unsigned long deadline;
	int todo;

	BUG_ON(EC_MSG_PREAMBLE_COUNT > ec_dev->din_size);

	/* Receive data until we see the header byte */
	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
	while (true) {
	unsigned long start_jiffies = jiffies;

	ret = receive_n_bytes(ec_dev,
	ec_dev->din,
	EC_MSG_PREAMBLE_COUNT);
	if (ret < 0)
	return ret;

	ptr = ec_dev->din;
	for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
	if (*ptr == EC_SPI_FRAME_START) {
	dev_dbg(ec_dev->dev, "msg found at %zd\n",
	ptr - ec_dev->din);
	break;
	}
	}
	if (ptr != end)
	break;

	/*
	* Use the time at the start of the loop as a timeout. This
	* gives us one last shot at getting the transfer and is useful
	* in case we got context switched out for a while.
	*/
	if (time_after(start_jiffies, deadline)) {
	dev_warn(ec_dev->dev, "EC failed to respond in time\n");
	return -ETIMEDOUT;
	}
	}

	/*
	* ptr now points to the header byte. Copy any valid data to the
	* start of our buffer
	*/
	todo = end - ++ptr;
	BUG_ON(todo < 0 \|\| todo > ec_dev->din_size);
	todo = min(todo, need_len);
	memmove(ec_dev->din, ptr, todo);
	ptr = ec_dev->din + todo;
	dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
	need_len, todo);
	need_len -= todo;

	/* If the entire response struct wasn't read, get the rest of it. */
	if (todo < sizeof(*response)) {
	ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo);
	if (ret < 0)
	return -EBADMSG;
	ptr += (sizeof(*response) - todo);
	todo = sizeof(*response);
	}

	response = (struct ec_host_response *)ec_dev->din;

	/* Abort if data_len is too large. */
	if (response->data_len > ec_dev->din_size)
	return -EMSGSIZE;

	/* Receive data until we have it all */
	while (need_len > 0) {
	/*
	* We can't support transfers larger than the SPI FIFO size
	* unless we have DMA. We don't have DMA on the ISP SPI ports
	* for Exynos. We need a way of asking SPI driver for
	* maximum-supported transfer size.
	*/
	todo = min(need_len, 256);
	dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
	todo, need_len, ptr - ec_dev->din);

	ret = receive_n_bytes(ec_dev, ptr, todo);
	if (ret < 0)
	return ret;

	ptr += todo;
	need_len -= todo;
	}

	dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);

	return 0;
	}

	/**
	* cros_ec_spi_receive_response - Receive a response from the EC.
	*
	* This function has two phases: reading the preamble bytes (since if we read
	* data from the EC before it is ready to send, we just get preamble) and
	* reading the actual message.
	*
	* The received data is placed into ec_dev->din.
	*
	* @ec_dev: ChromeOS EC device
	* @need_len: Number of message bytes we need to read
	*/
	static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
	int need_len)
	{
	u8 ptr, end;
	int ret;
	unsigned long deadline;
	int todo;

	BUG_ON(EC_MSG_PREAMBLE_COUNT > ec_dev->din_size);

	/* Receive data until we see the header byte */
	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
	while (true) {
	unsigned long start_jiffies = jiffies;

	ret = receive_n_bytes(ec_dev,
	ec_dev->din,
	EC_MSG_PREAMBLE_COUNT);
	if (ret < 0)
	return ret;

	ptr = ec_dev->din;
	for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
	if (*ptr == EC_SPI_FRAME_START) {
	dev_dbg(ec_dev->dev, "msg found at %zd\n",
	ptr - ec_dev->din);
	break;
	}
	}
	if (ptr != end)
	break;

	/*
	* Use the time at the start of the loop as a timeout. This
	* gives us one last shot at getting the transfer and is useful
	* in case we got context switched out for a while.
	*/
	if (time_after(start_jiffies, deadline)) {
	dev_warn(ec_dev->dev, "EC failed to respond in time\n");
	return -ETIMEDOUT;
	}
	}

	/*
	* ptr now points to the header byte. Copy any valid data to the
	* start of our buffer
	*/
	todo = end - ++ptr;
	BUG_ON(todo < 0 \|\| todo > ec_dev->din_size);
	todo = min(todo, need_len);
	memmove(ec_dev->din, ptr, todo);
	ptr = ec_dev->din + todo;
	dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
	need_len, todo);
	need_len -= todo;

	/* Receive data until we have it all */
	while (need_len > 0) {
	/*
	* We can't support transfers larger than the SPI FIFO size
	* unless we have DMA. We don't have DMA on the ISP SPI ports
	* for Exynos. We need a way of asking SPI driver for
	* maximum-supported transfer size.
	*/
	todo = min(need_len, 256);
	dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
	todo, need_len, ptr - ec_dev->din);

	ret = receive_n_bytes(ec_dev, ptr, todo);
	if (ret < 0)
	return ret;

	debug_packet(ec_dev->dev, "interim", ptr, todo);
	ptr += todo;
	need_len -= todo;
	}

	dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);

	return 0;
	}

	/**
	* cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
	*
	* @ec_dev: ChromeOS EC device
	* @ec_msg: Message to transfer
	*/
	static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
	struct cros_ec_command *ec_msg)
	{
	struct ec_host_request *request;
	struct ec_host_response *response;
	struct cros_ec_spi *ec_spi = ec_dev->priv;
	struct spi_transfer trans, trans_delay;
	struct spi_message msg;
	int i, len;
	u8 *ptr;
	u8 *rx_buf;
	u8 sum;
	int ret = 0, final_ret;

	len = cros_ec_prepare_tx(ec_dev, ec_msg);
	request = (struct ec_host_request *)ec_dev->dout;
	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);

	/* If it's too soon to do another transaction, wait */
	if (ec_spi->last_transfer_ns) {
	unsigned long delay; /* The delay completed so far */

	delay = ktime_get_ns() - ec_spi->last_transfer_ns;
	if (delay < EC_SPI_RECOVERY_TIME_NS)
	ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
	}

	rx_buf = kzalloc(len, GFP_KERNEL);
	if (!rx_buf) {
	ret = -ENOMEM;
	goto exit;
	}

	/*
	* Leave a gap between CS assertion and clocking of data to allow the
	* EC time to wakeup.
	*/
	spi_message_init(&msg);
	if (ec_spi->start_of_msg_delay) {
	memset(&trans_delay, 0, sizeof(trans_delay));
	trans_delay.delay_usecs = ec_spi->start_of_msg_delay;
	spi_message_add_tail(&trans_delay, &msg);
	}

	/* Transmit phase - send our message */
	memset(&trans, 0, sizeof(trans));
	trans.tx_buf = ec_dev->dout;
	trans.rx_buf = rx_buf;
	trans.len = len;
	trans.cs_change = 1;
	spi_message_add_tail(&trans, &msg);
	ret = spi_sync(ec_spi->spi, &msg);

	/* Get the response */
	if (!ret) {
	/* Verify that EC can process command */
	for (i = 0; i < len; i++) {
	switch (rx_buf[i]) {
	case EC_SPI_PAST_END:
	case EC_SPI_RX_BAD_DATA:
	case EC_SPI_NOT_READY:
	ret = -EAGAIN;
	ec_msg->result = EC_RES_IN_PROGRESS;
	default:
	break;
	}
	if (ret)
	break;
	}
	if (!ret)
	ret = cros_ec_spi_receive_packet(ec_dev,
	ec_msg->insize + sizeof(*response));
	} else {
	dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
	}

	final_ret = terminate_request(ec_dev);
	if (!ret)
	ret = final_ret;
	if (ret < 0)
	goto exit;

	ptr = ec_dev->din;

	/* check response error code */
	response = (struct ec_host_response *)ptr;
	ec_msg->result = response->result;

	ret = cros_ec_check_result(ec_dev, ec_msg);
	if (ret)
	goto exit;

	len = response->data_len;
	sum = 0;
	if (len > ec_msg->insize) {
	dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
	len, ec_msg->insize);
	ret = -EMSGSIZE;
	goto exit;
	}

	for (i = 0; i < sizeof(*response); i++)
	sum += ptr[i];

	/* copy response packet payload and compute checksum */
	memcpy(ec_msg->data, ptr + sizeof(*response), len);
	for (i = 0; i < len; i++)
	sum += ec_msg->data[i];

	if (sum) {
	dev_err(ec_dev->dev,
	"bad packet checksum, calculated %x\n",
	sum);
	ret = -EBADMSG;
	goto exit;
	}

	ret = len;
	exit:
	kfree(rx_buf);
	if (ec_msg->command == EC_CMD_REBOOT_EC)
	msleep(EC_REBOOT_DELAY_MS);

	return ret;
	}

	/**
	* cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
	*
	* @ec_dev: ChromeOS EC device
	* @ec_msg: Message to transfer
	*/
	static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
	struct cros_ec_command *ec_msg)
	{
	struct cros_ec_spi *ec_spi = ec_dev->priv;
	struct spi_transfer trans;
	struct spi_message msg;
	int i, len;
	u8 *ptr;
	u8 *rx_buf;
	int sum;
	int ret = 0, final_ret;

	len = cros_ec_prepare_tx(ec_dev, ec_msg);
	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);

	/* If it's too soon to do another transaction, wait */
	if (ec_spi->last_transfer_ns) {
	unsigned long delay; /* The delay completed so far */

	delay = ktime_get_ns() - ec_spi->last_transfer_ns;
	if (delay < EC_SPI_RECOVERY_TIME_NS)
	ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
	}

	rx_buf = kzalloc(len, GFP_KERNEL);
	if (!rx_buf) {
	ret = -ENOMEM;
	goto exit;
	}

	/* Transmit phase - send our message */
	debug_packet(ec_dev->dev, "out", ec_dev->dout, len);
	memset(&trans, 0, sizeof(trans));
	trans.tx_buf = ec_dev->dout;
	trans.rx_buf = rx_buf;
	trans.len = len;
	trans.cs_change = 1;
	spi_message_init(&msg);
	spi_message_add_tail(&trans, &msg);
	ret = spi_sync(ec_spi->spi, &msg);

	/* Get the response */
	if (!ret) {
	/* Verify that EC can process command */
	for (i = 0; i < len; i++) {
	switch (rx_buf[i]) {
	case EC_SPI_PAST_END:
	case EC_SPI_RX_BAD_DATA:
	case EC_SPI_NOT_READY:
	ret = -EAGAIN;
	ec_msg->result = EC_RES_IN_PROGRESS;
	default:
	break;
	}
	if (ret)
	break;
	}
	if (!ret)
	ret = cros_ec_spi_receive_response(ec_dev,
	ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
	} else {
	dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
	}

	final_ret = terminate_request(ec_dev);
	if (!ret)
	ret = final_ret;
	if (ret < 0)
	goto exit;

	ptr = ec_dev->din;

	/* check response error code */
	ec_msg->result = ptr[0];
	ret = cros_ec_check_result(ec_dev, ec_msg);
	if (ret)
	goto exit;

	len = ptr[1];
	sum = ptr[0] + ptr[1];
	if (len > ec_msg->insize) {
	dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
	len, ec_msg->insize);
	ret = -ENOSPC;
	goto exit;
	}

	/* copy response packet payload and compute checksum */
	for (i = 0; i < len; i++) {
	sum += ptr[i + 2];
	if (ec_msg->insize)
	ec_msg->data[i] = ptr[i + 2];
	}
	sum &= 0xff;

	debug_packet(ec_dev->dev, "in", ptr, len + 3);

	if (sum != ptr[len + 2]) {
	dev_err(ec_dev->dev,
	"bad packet checksum, expected %02x, got %02x\n",
	sum, ptr[len + 2]);
	ret = -EBADMSG;
	goto exit;
	}

	ret = len;
	exit:
	kfree(rx_buf);
	if (ec_msg->command == EC_CMD_REBOOT_EC)
	msleep(EC_REBOOT_DELAY_MS);

	return ret;
	}

	static void cros_ec_spi_dt_probe(struct cros_ec_spi ec_spi, struct device dev)
	{
	struct device_node *np = dev->of_node;
	u32 val;
	int ret;

	ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
	if (!ret)
	ec_spi->start_of_msg_delay = val;

	ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
	if (!ret)
	ec_spi->end_of_msg_delay = val;
	}

	static int cros_ec_spi_probe(struct spi_device *spi)
	{
	struct device *dev = &spi->dev;
	struct cros_ec_device *ec_dev;
	struct cros_ec_spi *ec_spi;
	int err;

	spi->bits_per_word = 8;
	spi->mode = SPI_MODE_0;
	err = spi_setup(spi);
	if (err < 0)
	return err;

	ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL);
	if (ec_spi == NULL)
	return -ENOMEM;
	ec_spi->spi = spi;
	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
	if (!ec_dev)
	return -ENOMEM;

	/* Check for any DT properties */
	cros_ec_spi_dt_probe(ec_spi, dev);

	spi_set_drvdata(spi, ec_dev);
	ec_dev->dev = dev;
	ec_dev->priv = ec_spi;
	ec_dev->irq = spi->irq;
	ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
	ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
	ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
	ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
	sizeof(struct ec_host_response) +
	sizeof(struct ec_response_get_protocol_info);
	ec_dev->dout_size = sizeof(struct ec_host_request);


	err = cros_ec_register(ec_dev);
	if (err) {
	dev_err(dev, "cannot register EC\n");
	return err;
	}

	device_init_wakeup(&spi->dev, true);

	return 0;
	}

	static int cros_ec_spi_remove(struct spi_device *spi)
	{
	struct cros_ec_device *ec_dev;

	ec_dev = spi_get_drvdata(spi);
	cros_ec_remove(ec_dev);

	return 0;
	}

	#ifdef CONFIG_PM_SLEEP
	static int cros_ec_spi_suspend(struct device *dev)
	{
	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);

	return cros_ec_suspend(ec_dev);
	}

	static int cros_ec_spi_resume(struct device *dev)
	{
	struct cros_ec_device *ec_dev = dev_get_drvdata(dev);

	return cros_ec_resume(ec_dev);
	}
	#endif

	static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
	cros_ec_spi_resume);

	static const struct of_device_id cros_ec_spi_of_match[] = {
	{ .compatible = "google,cros-ec-spi", },
	{ /* sentinel */ },
	};
	MODULE_DEVICE_TABLE(of, cros_ec_spi_of_match);

	static const struct spi_device_id cros_ec_spi_id[] = {
	{ "cros-ec-spi", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);

	static struct spi_driver cros_ec_driver_spi = {
	.driver = {
	.name = "cros-ec-spi",
	.of_match_table = of_match_ptr(cros_ec_spi_of_match),
	.pm = &cros_ec_spi_pm_ops,
	},
	.probe = cros_ec_spi_probe,
	.remove = cros_ec_spi_remove,
	.id_table = cros_ec_spi_id,
	};

	module_spi_driver(cros_ec_driver_spi);

	MODULE_LICENSE("GPL v2");
	MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)");