1 files changed, 440 insertions, 0 deletions
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
new file mode 100644
index 00000000000..0b8d3282916
--- /dev/null
+++ b/drivers/mfd/cros_ec_spi.c
@@ -0,0 +1,440 @@
+/*
+ * 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
+ * @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.
+ * @lock: mutex to ensure only one user of cros_ec_command_spi_xfer at a time
+ */
+struct cros_ec_spi {
+	struct spi_device *spi;
+	s64 last_transfer_ns;
+	unsigned int end_of_msg_delay;
+	struct mutex lock;
+};
+
+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
+}
+
+/**
+ * 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)
+{
+	struct cros_ec_spi *ec_spi = ec_dev->priv;
+	struct spi_transfer trans;
+	struct spi_message msg;
+	u8 *ptr, *end;
+	int ret;
+	unsigned long deadline;
+	int todo;
+
+	/* Receive data until we see the header byte */
+	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
+	while (true) {
+		unsigned long start_jiffies = jiffies;
+
+		memset(&trans, 0, sizeof(trans));
+		trans.cs_change = 1;
+		trans.rx_buf = ptr = ec_dev->din;
+		trans.len = EC_MSG_PREAMBLE_COUNT;
+
+		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;
+		}
+
+		for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
+			if (*ptr == EC_MSG_HEADER) {
+				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);
+
+		memset(&trans, 0, sizeof(trans));
+		trans.cs_change = 1;
+		trans.rx_buf = ptr;
+		trans.len = todo;
+		spi_message_init(&msg);
+		spi_message_add_tail(&trans, &msg);
+
+		/* send command to EC and read answer */
+		BUG_ON((u8 *)trans.rx_buf - ec_dev->din + todo >
+				ec_dev->din_size);
+		ret = spi_sync(ec_spi->spi, &msg);
+		if (ret < 0) {
+			dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
+			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_command_spi_xfer - Transfer a message over SPI and receive the reply
+ *
+ * @ec_dev: ChromeOS EC device
+ * @ec_msg: Message to transfer
+ */
+static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
+				    struct cros_ec_msg *ec_msg)
+{
+	struct cros_ec_spi *ec_spi = ec_dev->priv;
+	struct spi_transfer trans;
+	struct spi_message msg;
+	int i, len;
+	u8 *ptr;
+	int sum;
+	int ret = 0, final_ret;
+	struct timespec ts;
+
+	/*
+	 * We have the shared ec_dev buffer plus we do lots of separate spi_sync
+	 * calls, so we need to make sure only one person is using this at a
+	 * time.
+	 */
+	mutex_lock(&ec_spi->lock);
+
+	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) {
+		struct timespec ts;
+		unsigned long delay;	/* The delay completed so far */
+
+		ktime_get_ts(&ts);
+		delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns;
+		if (delay < EC_SPI_RECOVERY_TIME_NS)
+			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
+	}
+
+	/* 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.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) {
+		ret = cros_ec_spi_receive_response(ec_dev,
+				ec_msg->in_len + EC_MSG_TX_PROTO_BYTES);
+	} else {
+		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
+	}
+
+	/* turn off CS */
+	spi_message_init(&msg);
+
+	if (ec_spi->end_of_msg_delay) {
+		/*
+		 * Add delay for last transaction, to ensure the rising edge
+		 * doesn't come too soon after the end of the data.
+		 */
+		memset(&trans, 0, sizeof(trans));
+		trans.delay_usecs = ec_spi->end_of_msg_delay;
+		spi_message_add_tail(&trans, &msg);
+	}
+
+	final_ret = spi_sync(ec_spi->spi, &msg);
+	ktime_get_ts(&ts);
+	ec_spi->last_transfer_ns = timespec_to_ns(&ts);
+	if (!ret)
+		ret = final_ret;
+	if (ret < 0) {
+		dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
+		goto exit;
+	}
+
+	/* check response error code */
+	ptr = ec_dev->din;
+	if (ptr[0]) {
+		dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n",
+			 ec_msg->cmd, ptr[0]);
+		debug_packet(ec_dev->dev, "in_err", ptr, len);
+		ret = -EINVAL;
+		goto exit;
+	}
+	len = ptr[1];
+	sum = ptr[0] + ptr[1];
+	if (len > ec_msg->in_len) {
+		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
+			len, ec_msg->in_len);
+		ret = -ENOSPC;
+		goto exit;
+	}
+
+	/* copy response packet payload and compute checksum */
+	for (i = 0; i < len; i++) {
+		sum += ptr[i + 2];
+		if (ec_msg->in_len)
+			ec_msg->in_buf[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 = 0;
+exit:
+	mutex_unlock(&ec_spi->lock);
+	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-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;
+	mutex_init(&ec_spi->lock);
+	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->name = "SPI";
+	ec_dev->dev = dev;
+	ec_dev->priv = ec_spi;
+	ec_dev->irq = spi->irq;
+	ec_dev->command_xfer = cros_ec_command_spi_xfer;
+	ec_dev->ec_name = ec_spi->spi->modalias;
+	ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
+	ec_dev->parent = &ec_spi->spi->dev;
+	ec_dev->din_size = EC_MSG_BYTES + EC_MSG_PREAMBLE_COUNT;
+	ec_dev->dout_size = EC_MSG_BYTES;
+
+	err = cros_ec_register(ec_dev);
+	if (err) {
+		dev_err(dev, "cannot register EC\n");
+		return err;
+	}
+
+	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 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",
+		.owner	= THIS_MODULE,
+		.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)");