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