--- /dev/null
+/*
+ * 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)
+
+/*
+ * The EC is unresponsive for a time after a reboot command. Add a
+ * simple delay to make sure that the bus stays locked.
+ */
+#define EC_REBOOT_DELAY_MS 50
+
+/**
+ * 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.
+ */
+struct cros_ec_spi {
+ struct spi_device *spi;
+ s64 last_transfer_ns;
+ 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
+}
+
+/**
+ * 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_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;
+ 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);
+ }
+
+ /* 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->insize + EC_MSG_TX_PROTO_BYTES);
+ } else {
+ dev_err(ec_dev->dev, "spi transfer failed: %d\n", 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);
+
+ final_ret = spi_sync(ec_spi->spi, &msg);
+ ec_spi->last_transfer_ns = ktime_get_ns();
+ if (!ret)
+ ret = final_ret;
+ if (ret < 0) {
+ dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
+ 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->indata[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:
+ 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-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->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;
+ }
+
+ 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 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)");
Code Review / kvmfornfv.git / blobdiff