diff options
Diffstat (limited to 'drivers/iio/imu/bno055/bno055_ser_core.c')
-rw-r--r-- | drivers/iio/imu/bno055/bno055_ser_core.c | 560 |
1 files changed, 560 insertions, 0 deletions
diff --git a/drivers/iio/imu/bno055/bno055_ser_core.c b/drivers/iio/imu/bno055/bno055_ser_core.c new file mode 100644 index 0000000000..57728a5684 --- /dev/null +++ b/drivers/iio/imu/bno055/bno055_ser_core.c @@ -0,0 +1,560 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Serial line interface for Bosh BNO055 IMU (via serdev). + * This file implements serial communication up to the register read/write + * level. + * + * Copyright (C) 2021-2022 Istituto Italiano di Tecnologia + * Electronic Design Laboratory + * Written by Andrea Merello <andrea.merello@iit.it> + * + * This driver is based on + * Plantower PMS7003 particulate matter sensor driver + * Which is + * Copyright (c) Tomasz Duszynski <tduszyns@gmail.com> + */ + +#include <linux/completion.h> +#include <linux/device.h> +#include <linux/errno.h> +#include <linux/jiffies.h> +#include <linux/kernel.h> +#include <linux/mod_devicetable.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/regmap.h> +#include <linux/serdev.h> + +#include "bno055_ser_trace.h" +#include "bno055.h" + +/* + * Register writes cmd have the following format + * +------+------+-----+-----+----- ... ----+ + * | 0xAA | 0xOO | REG | LEN | payload[LEN] | + * +------+------+-----+-----+----- ... ----+ + * + * Register write responses have the following format + * +------+----------+ + * | 0xEE | ERROCODE | + * +------+----------+ + * + * .. except when writing the SYS_RST bit (i.e. triggering a system reset); in + * case the IMU accepts the command, then it resets without responding. We don't + * handle this (yet) here (so we inform the common bno055 code not to perform + * sw resets - bno055 on serial bus basically requires the hw reset pin). + * + * Register read have the following format + * +------+------+-----+-----+ + * | 0xAA | 0xO1 | REG | LEN | + * +------+------+-----+-----+ + * + * Successful register read response have the following format + * +------+-----+----- ... ----+ + * | 0xBB | LEN | payload[LEN] | + * +------+-----+----- ... ----+ + * + * Failed register read response have the following format + * +------+--------+ + * | 0xEE | ERRCODE| (ERRCODE always > 1) + * +------+--------+ + * + * Error codes are + * 01: OK + * 02: read/write FAIL + * 04: invalid address + * 05: write on RO + * 06: wrong start byte + * 07: bus overrun + * 08: len too high + * 09: len too low + * 10: bus RX byte timeout (timeout is 30mS) + * + * + * **WORKAROUND ALERT** + * + * Serial communication seems very fragile: the BNO055 buffer seems to overflow + * very easy; BNO055 seems able to sink few bytes, then it needs a brief pause. + * On the other hand, it is also picky on timeout: if there is a pause > 30mS in + * between two bytes then the transaction fails (IMU internal RX FSM resets). + * + * BNO055 has been seen also failing to process commands in case we send them + * too close each other (or if it is somehow busy?) + * + * In particular I saw these scenarios: + * 1) If we send 2 bytes per time, then the IMU never(?) overflows. + * 2) If we send 4 bytes per time (i.e. the full header), then the IMU could + * overflow, but it seem to sink all 4 bytes, then it returns error. + * 3) If we send more than 4 bytes, the IMU could overflow, and I saw it sending + * error after 4 bytes are sent; we have troubles in synchronizing again, + * because we are still sending data, and the IMU interprets it as the 1st + * byte of a new command. + * + * While we must avoid case 3, we could send 4 bytes per time and eventually + * retry in case of failure; this seemed convenient for reads (which requires + * TXing exactly 4 bytes), however it has been seen that, depending by the IMU + * settings (e.g. LPF), failures became less or more frequent; in certain IMU + * configurations they are very rare, but in certain others we keeps failing + * even after like 30 retries. + * + * So, we just split TXes in [2-bytes + delay] steps, and still keep an eye on + * the IMU response; in case it overflows (which is now unlikely), we retry. + */ + +/* + * Read operation overhead: + * 4 bytes req + 2byte resp hdr. + * 6 bytes = 60 bit (considering 1start + 1stop bits). + * 60/115200 = ~520uS + about 2500mS delay -> ~3mS + * In 3mS we could read back about 34 bytes that means 17 samples, this means + * that in case of scattered reads in which the gap is 17 samples or less it is + * still convenient to go for a burst. + * We have to take into account also IMU response time - IMU seems to be often + * reasonably quick to respond, but sometimes it seems to be in some "critical + * section" in which it delays handling of serial protocol. Because of this we + * round-up to 22, which is the max number of samples, always bursting indeed. + */ +#define BNO055_SER_XFER_BURST_BREAK_THRESHOLD 22 + +struct bno055_ser_priv { + enum { + CMD_NONE, + CMD_READ, + CMD_WRITE, + } expect_response; + int expected_data_len; + u8 *response_buf; + + /** + * enum cmd_status - represent the status of a command sent to the HW. + * @STATUS_CRIT: The command failed: the serial communication failed. + * @STATUS_OK: The command executed successfully. + * @STATUS_FAIL: The command failed: HW responded with an error. + */ + enum { + STATUS_CRIT = -1, + STATUS_OK = 0, + STATUS_FAIL = 1, + } cmd_status; + + /* + * Protects all the above fields, which are accessed in behalf of both + * the serdev RX callback and the regmap side + */ + struct mutex lock; + + /* Only accessed in serdev RX callback context*/ + struct { + enum { + RX_IDLE, + RX_START, + RX_DATA, + } state; + int databuf_count; + int expected_len; + int type; + } rx; + + /* Never accessed in behalf of serdev RX callback context */ + bool cmd_stale; + + struct completion cmd_complete; + struct serdev_device *serdev; +}; + +static int bno055_ser_send_chunk(struct bno055_ser_priv *priv, const u8 *data, int len) +{ + int ret; + + trace_send_chunk(len, data); + ret = serdev_device_write(priv->serdev, data, len, msecs_to_jiffies(25)); + if (ret < 0) + return ret; + + if (ret < len) + return -EIO; + + return 0; +} + +/* + * Send a read or write command. + * 'data' can be NULL (used in read case). 'len' parameter is always valid; in + * case 'data' is non-NULL then it must match 'data' size. + */ +static int bno055_ser_do_send_cmd(struct bno055_ser_priv *priv, + bool read, int addr, int len, const u8 *data) +{ + u8 hdr[] = {0xAA, read, addr, len}; + int chunk_len; + int ret; + + ret = bno055_ser_send_chunk(priv, hdr, 2); + if (ret) + goto fail; + usleep_range(2000, 3000); + ret = bno055_ser_send_chunk(priv, hdr + 2, 2); + if (ret) + goto fail; + + if (read) + return 0; + + while (len) { + chunk_len = min(len, 2); + usleep_range(2000, 3000); + ret = bno055_ser_send_chunk(priv, data, chunk_len); + if (ret) + goto fail; + data += chunk_len; + len -= chunk_len; + } + + return 0; +fail: + /* waiting more than 30mS should clear the BNO055 internal state */ + usleep_range(40000, 50000); + return ret; +} + +static int bno055_ser_send_cmd(struct bno055_ser_priv *priv, + bool read, int addr, int len, const u8 *data) +{ + const int retry_max = 5; + int retry = retry_max; + int ret = 0; + + /* + * In case previous command was interrupted we still need to wait it to + * complete before we can issue new commands + */ + if (priv->cmd_stale) { + ret = wait_for_completion_interruptible_timeout(&priv->cmd_complete, + msecs_to_jiffies(100)); + if (ret == -ERESTARTSYS) + return -ERESTARTSYS; + + priv->cmd_stale = false; + /* if serial protocol broke, bail out */ + if (priv->cmd_status == STATUS_CRIT) + return -EIO; + } + + /* + * Try to convince the IMU to cooperate.. as explained in the comments + * at the top of this file, the IMU could also refuse the command (i.e. + * it is not ready yet); retry in this case. + */ + do { + mutex_lock(&priv->lock); + priv->expect_response = read ? CMD_READ : CMD_WRITE; + reinit_completion(&priv->cmd_complete); + mutex_unlock(&priv->lock); + + if (retry != retry_max) + trace_cmd_retry(read, addr, retry_max - retry); + ret = bno055_ser_do_send_cmd(priv, read, addr, len, data); + if (ret) + continue; + + ret = wait_for_completion_interruptible_timeout(&priv->cmd_complete, + msecs_to_jiffies(100)); + if (ret == -ERESTARTSYS) { + priv->cmd_stale = true; + return -ERESTARTSYS; + } + + if (!ret) + return -ETIMEDOUT; + + if (priv->cmd_status == STATUS_OK) + return 0; + if (priv->cmd_status == STATUS_CRIT) + return -EIO; + + /* loop in case priv->cmd_status == STATUS_FAIL */ + } while (--retry); + + if (ret < 0) + return ret; + if (priv->cmd_status == STATUS_FAIL) + return -EINVAL; + return 0; +} + +static int bno055_ser_write_reg(void *context, const void *_data, size_t count) +{ + const u8 *data = _data; + struct bno055_ser_priv *priv = context; + + if (count < 2) { + dev_err(&priv->serdev->dev, "Invalid write count %zu", count); + return -EINVAL; + } + + trace_write_reg(data[0], data[1]); + return bno055_ser_send_cmd(priv, 0, data[0], count - 1, data + 1); +} + +static int bno055_ser_read_reg(void *context, + const void *_reg, size_t reg_size, + void *val, size_t val_size) +{ + int ret; + int reg_addr; + const u8 *reg = _reg; + struct bno055_ser_priv *priv = context; + + if (val_size > 128) { + dev_err(&priv->serdev->dev, "Invalid read valsize %zu", val_size); + return -EINVAL; + } + + reg_addr = *reg; + trace_read_reg(reg_addr, val_size); + mutex_lock(&priv->lock); + priv->expected_data_len = val_size; + priv->response_buf = val; + mutex_unlock(&priv->lock); + + ret = bno055_ser_send_cmd(priv, 1, reg_addr, val_size, NULL); + + mutex_lock(&priv->lock); + priv->response_buf = NULL; + mutex_unlock(&priv->lock); + + return ret; +} + +/* + * Handler for received data; this is called from the receiver callback whenever + * it got some packet from the serial bus. The status tells us whether the + * packet is valid (i.e. header ok && received payload len consistent wrt the + * header). It's now our responsibility to check whether this is what we + * expected, of whether we got some unexpected, yet valid, packet. + */ +static void bno055_ser_handle_rx(struct bno055_ser_priv *priv, int status) +{ + mutex_lock(&priv->lock); + switch (priv->expect_response) { + case CMD_NONE: + dev_warn(&priv->serdev->dev, "received unexpected, yet valid, data from sensor"); + mutex_unlock(&priv->lock); + return; + + case CMD_READ: + priv->cmd_status = status; + if (status == STATUS_OK && + priv->rx.databuf_count != priv->expected_data_len) { + /* + * If we got here, then the lower layer serial protocol + * seems consistent with itself; if we got an unexpected + * amount of data then signal it as a non critical error + */ + priv->cmd_status = STATUS_FAIL; + dev_warn(&priv->serdev->dev, + "received an unexpected amount of, yet valid, data from sensor"); + } + break; + + case CMD_WRITE: + priv->cmd_status = status; + break; + } + + priv->expect_response = CMD_NONE; + mutex_unlock(&priv->lock); + complete(&priv->cmd_complete); +} + +/* + * Serdev receiver FSM. This tracks the serial communication and parse the + * header. It pushes packets to bno055_ser_handle_rx(), eventually communicating + * failures (i.e. malformed packets). + * Ideally it doesn't know anything about upper layer (i.e. if this is the + * packet we were really expecting), but since we copies the payload into the + * receiver buffer (that is not valid when i.e. we don't expect data), we + * snoop a bit in the upper layer.. + * Also, we assume to RX one pkt per time (i.e. the HW doesn't send anything + * unless we require to AND we don't queue more than one request per time). + */ +static int bno055_ser_receive_buf(struct serdev_device *serdev, + const unsigned char *buf, size_t size) +{ + int status; + struct bno055_ser_priv *priv = serdev_device_get_drvdata(serdev); + int remaining = size; + + if (size == 0) + return 0; + + trace_recv(size, buf); + switch (priv->rx.state) { + case RX_IDLE: + /* + * New packet. + * Check for its 1st byte that identifies the pkt type. + */ + if (buf[0] != 0xEE && buf[0] != 0xBB) { + dev_err(&priv->serdev->dev, + "Invalid packet start %x", buf[0]); + bno055_ser_handle_rx(priv, STATUS_CRIT); + break; + } + priv->rx.type = buf[0]; + priv->rx.state = RX_START; + remaining--; + buf++; + priv->rx.databuf_count = 0; + fallthrough; + + case RX_START: + /* + * Packet RX in progress, we expect either 1-byte len or 1-byte + * status depending by the packet type. + */ + if (remaining == 0) + break; + + if (priv->rx.type == 0xEE) { + if (remaining > 1) { + dev_err(&priv->serdev->dev, "EE pkt. Extra data received"); + status = STATUS_CRIT; + } else { + status = (buf[0] == 1) ? STATUS_OK : STATUS_FAIL; + } + bno055_ser_handle_rx(priv, status); + priv->rx.state = RX_IDLE; + break; + + } else { + /*priv->rx.type == 0xBB */ + priv->rx.state = RX_DATA; + priv->rx.expected_len = buf[0]; + remaining--; + buf++; + } + fallthrough; + + case RX_DATA: + /* Header parsed; now receiving packet data payload */ + if (remaining == 0) + break; + + if (priv->rx.databuf_count + remaining > priv->rx.expected_len) { + /* + * This is an inconsistency in serial protocol, we lost + * sync and we don't know how to handle further data + */ + dev_err(&priv->serdev->dev, "BB pkt. Extra data received"); + bno055_ser_handle_rx(priv, STATUS_CRIT); + priv->rx.state = RX_IDLE; + break; + } + + mutex_lock(&priv->lock); + /* + * NULL e.g. when read cmd is stale or when no read cmd is + * actually pending. + */ + if (priv->response_buf && + /* + * Snoop on the upper layer protocol stuff to make sure not + * to write to an invalid memory. Apart for this, let's the + * upper layer manage any inconsistency wrt expected data + * len (as long as the serial protocol is consistent wrt + * itself (i.e. response header is consistent with received + * response len. + */ + (priv->rx.databuf_count + remaining <= priv->expected_data_len)) + memcpy(priv->response_buf + priv->rx.databuf_count, + buf, remaining); + mutex_unlock(&priv->lock); + + priv->rx.databuf_count += remaining; + + /* + * Reached expected len advertised by the IMU for the current + * packet. Pass it to the upper layer (for us it is just valid). + */ + if (priv->rx.databuf_count == priv->rx.expected_len) { + bno055_ser_handle_rx(priv, STATUS_OK); + priv->rx.state = RX_IDLE; + } + break; + } + + return size; +} + +static const struct serdev_device_ops bno055_ser_serdev_ops = { + .receive_buf = bno055_ser_receive_buf, + .write_wakeup = serdev_device_write_wakeup, +}; + +static struct regmap_bus bno055_ser_regmap_bus = { + .write = bno055_ser_write_reg, + .read = bno055_ser_read_reg, +}; + +static int bno055_ser_probe(struct serdev_device *serdev) +{ + struct bno055_ser_priv *priv; + struct regmap *regmap; + int ret; + + priv = devm_kzalloc(&serdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + serdev_device_set_drvdata(serdev, priv); + priv->serdev = serdev; + mutex_init(&priv->lock); + init_completion(&priv->cmd_complete); + + serdev_device_set_client_ops(serdev, &bno055_ser_serdev_ops); + ret = devm_serdev_device_open(&serdev->dev, serdev); + if (ret) + return ret; + + if (serdev_device_set_baudrate(serdev, 115200) != 115200) { + dev_err(&serdev->dev, "Cannot set required baud rate"); + return -EIO; + } + + ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE); + if (ret) { + dev_err(&serdev->dev, "Cannot set required parity setting"); + return ret; + } + serdev_device_set_flow_control(serdev, false); + + regmap = devm_regmap_init(&serdev->dev, &bno055_ser_regmap_bus, + priv, &bno055_regmap_config); + if (IS_ERR(regmap)) + return dev_err_probe(&serdev->dev, PTR_ERR(regmap), + "Unable to init register map"); + + return bno055_probe(&serdev->dev, regmap, + BNO055_SER_XFER_BURST_BREAK_THRESHOLD, false); +} + +static const struct of_device_id bno055_ser_of_match[] = { + { .compatible = "bosch,bno055" }, + { } +}; +MODULE_DEVICE_TABLE(of, bno055_ser_of_match); + +static struct serdev_device_driver bno055_ser_driver = { + .driver = { + .name = "bno055-ser", + .of_match_table = bno055_ser_of_match, + }, + .probe = bno055_ser_probe, +}; +module_serdev_device_driver(bno055_ser_driver); + +MODULE_AUTHOR("Andrea Merello <andrea.merello@iit.it>"); +MODULE_DESCRIPTION("Bosch BNO055 serdev interface"); +MODULE_IMPORT_NS(IIO_BNO055); +MODULE_LICENSE("GPL"); |