USB device stack, with KL25Z fixes for USB 3.0 hosts and sleep/resume interrupt handling

Dependents:   frdm_Slider_Keyboard idd_hw2_figlax_PanType idd_hw2_appachu_finger_chording idd_hw3_AngieWangAntonioDeLimaFernandesDanielLim_BladeSymphony ... more

Fork of USBDevice by mbed official

This is an overhauled version of the standard mbed USB device-side driver library, with bug fixes for KL25Z devices. It greatly improves reliability and stability of USB on the KL25Z, especially with devices using multiple endpoints concurrently.

I've had some nagging problems with the base mbed implementation for a long time, manifesting as occasional random disconnects that required rebooting the device. Recently (late 2015), I started implementing a USB device on the KL25Z that used multiple endpoints, and suddenly the nagging, occasional problems turned into frequent and predictable crashes. This forced me to delve into the USB stack and figure out what was really going on. Happily, the frequent crashes made it possible to track down and fix the problems. This new version is working very reliably in my testing - the random disconnects seem completely eradicated, even under very stressful conditions for the device.

Summary

  • Overall stability improvements
  • USB 3.0 host support
  • Stalled endpoint fixes
  • Sleep/resume notifications
  • Smaller memory footprint
  • General code cleanup

Update - 2/15/2016

My recent fixes introduced a new problem that made the initial connection fail most of the time on certain hosts. It's not clear if the common thread was a particular type of motherboard or USB chip set, or a specific version of Windows, or what, but several people ran into it. We tracked the problem down to the "stall" fixes in the earlier updates, which we now know weren't quite the right fixes after all. The latest update (2/15/2016) fixes this. It has new and improved "unstall" handling that so far works well with diverse hosts.

Race conditions and overall stability

The base mbed KL25Z implementation has a lot of problems with "race conditions" - timing problems that can happen when hardware interrupts occur at inopportune moments. The library shares a bunch of static variable data between interrupt handler context and regular application context. This isn't automatically a bad thing, but it does require careful coordination to make sure that the interrupt handler doesn't corrupt data that the other code was in the middle of updating when an interrupt occurs. The base mbed code, though, doesn't do any of the necessary coordination. This makes it kind of amazing that the base code worked at all for anyone, but I guess the interrupt rate is low enough in most applications that the glitch rate was below anyone's threshold to seriously investigate.

This overhaul adds the necessary coordination for the interrupt handlers to protect against these data corruptions. I think it's very solid now, and hopefully entirely free of the numerous race conditions in the old code. It's always hard to be certain that you've fixed every possible bug like this because they strike (effectively) at random, but I'm pretty confident: my test application was reliably able to trigger glitches in the base code in a matter of minutes, but the same application (with the overhauled library) now runs for days on end without dropping the connection.

Stalled endpoint fixes

USB has a standard way of handling communications errors called a "stall", which basically puts the connection into an error mode to let both sides know that they need to reset their internal states and sync up again. The original mbed version of the USB device library doesn't seem to have the necessary code to recover from this condition properly. The KL25Z hardware does some of the work, but it also seems to require the software to take some steps to "un-stall" the connection. (I keep saying "seems to" because the hardware reference material is very sketchy about all of this. Most of what I've figured out is from observing the device in action with a Windows host.) This new version adds code to do the necessary re-syncing and get the connection going again, automatically, and transparently to the user.

USB 3.0 Hosts

The original mbed code sometimes didn't work when connecting to hosts with USB 3.0 ports. This didn't affect every host, but it affected many of them. The common element seemed to be the Intel Haswell chip set on the host, but there may be other chip sets affected as well. In any case, the problem affected many PCs from the Windows 7 and 8 generation, as well as many Macs. It was possible to work around the problem by avoiding USB 3.0 ports - you could use a USB 2 port on the host, or plug a USB 2 hub between the host and device. But I wanted to just fix the problem and eliminate the need for such workarounds. This modified version of the library has such a fix, which so far has worked for everyone who's tried.

Sleep/resume notifications

This modified version also contains an innocuous change to the KL25Z USB HAL code to handle sleep and resume interrupts with calls to suspendStateChanged(). The original KL25Z code omitted these calls (and in fact didn't even enable the interrupts), but I think this was an unintentional oversight - the notifier function is part of the generic API, and other supported boards all implement it. I use this feature in my own application so that I can distinguish sleep mode from actual disconnects and handle the two conditions correctly.

Smaller memory footprint

The base mbed version of the code allocates twice as much memory for USB buffers as it really needed to. It looks like the original developers intended to implement the KL25Z USB hardware's built-in double-buffering mechanism, but they ultimately abandoned that effort. But they left in the double memory allocation. This version removes that and allocates only what's actually needed. The USB buffers aren't that big (128 bytes per endpoint), so this doesn't save a ton of memory, but even a little memory is pretty precious on this machine given that it only has 16K.

(I did look into adding the double-buffering support that the original developers abandoned, but after some experimentation I decided they were right to skip it. It just doesn't seem to mesh well with the design of the rest of the mbed USB code. I think it would take a major rewrite to make it work, and it doesn't seem worth the effort given that most applications don't need it - it would only benefit applications that are moving so much data through USB that they're pushing the limits of the CPU. And even for those, I think it would be a lot simpler to build a purely software-based buffer rotation mechanism.)

General code cleanup

The KL25Z HAL code in this version has greatly expanded commentary and a lot of general cleanup. Some of the hardware constants were given the wrong symbolic names (e.g., EVEN and ODD were reversed), and many were just missing (written as hard-coded numbers without explanation). I fixed the misnomers and added symbolic names for formerly anonymous numbers. Hopefully the next person who has to overhaul this code will at least have an easier time understanding what I thought I was doing!

USBMSD/USBMSD.h

Committer:
mjr
Date:
2016-02-26
Revision:
49:03527ce6840e
Parent:
25:7c72828865f3

File content as of revision 49:03527ce6840e:

/* Copyright (c) 2010-2011 mbed.org, MIT License
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or
* substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
* BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/


#ifndef USBMSD_H
#define USBMSD_H

/* These headers are included for child class. */
#include "USBEndpoints.h"
#include "USBDescriptor.h"
#include "USBDevice_Types.h"

#include "USBDevice.h"

/**
 * USBMSD class: generic class in order to use all kinds of blocks storage chip
 *
 * Introduction
 *
 * The USBMSD implements the MSD protocol. It permits to access a memory chip (flash, sdcard,...)
 * from a computer over USB. But this class doesn't work standalone, you need to subclass this class
 * and define virtual functions which are called in USBMSD.
 *
 * How to use this class with your chip ?
 *
 * You have to inherit and define some pure virtual functions (mandatory step):
 *   - virtual int disk_read(char * data, int block): function to read a block
 *   - virtual int disk_write(const char * data, int block): function to write a block
 *   - virtual int disk_initialize(): function to initialize the memory
 *   - virtual int disk_sectors(): return the number of blocks
 *   - virtual int disk_size(): return the memory size
 *   - virtual int disk_status(): return the status of the storage chip (0: OK, 1: not initialized, 2: no medium in the drive, 4: write protection)
 *
 * All functions names are compatible with the fat filesystem library. So you can imagine using your own class with
 * USBMSD and the fat filesystem library in the same program. Just be careful because there are two different parts which
 * will access the sd card. You can do a master/slave system using the disk_status method.
 *
 * Once these functions defined, you can call connect() (at the end of the constructor of your class for instance)
 * of USBMSD to connect your mass storage device. connect() will first call disk_status() to test the status of the disk.
 * If disk_status() returns 1 (disk not initialized), then disk_initialize() is called. After this step, connect() will collect information
 * such as the number of blocks and the memory size.
 */
class USBMSD: public USBDevice {
public:

    /**
    * Constructor
    *
    * @param vendor_id Your vendor_id
    * @param product_id Your product_id
    * @param product_release Your preoduct_release
    */
    USBMSD(uint16_t vendor_id = 0x0703, uint16_t product_id = 0x0104, uint16_t product_release = 0x0001);

    /**
    * Connect the USB MSD device. Establish disk initialization before really connect the device.
    *
    * @param blocking if not configured
    * @returns true if successful
    */
    bool connect(bool blocking = true);

    /**
    * Disconnect the USB MSD device.
    */
    void disconnect();

    /**
    * Destructor
    */
    ~USBMSD();

protected:

    /*
    * read a block on a storage chip
    *
    * @param data pointer where will be stored read data
    * @param block block number
    * @returns 0 if successful
    */
    virtual int disk_read(uint8_t * data, uint64_t block) = 0;

    /*
    * write a block on a storage chip
    *
    * @param data data to write
    * @param block block number
    * @returns 0 if successful
    */
    virtual int disk_write(const uint8_t * data, uint64_t block) = 0;

    /*
    * Disk initilization
    */
    virtual int disk_initialize() = 0;

    /*
    * Return the number of blocks
    *
    * @returns number of blocks
    */
    virtual uint64_t disk_sectors() = 0;

    /*
    * Return memory size
    *
    * @returns memory size
    */
    virtual uint64_t disk_size() = 0;


    /*
    * To check the status of the storage chip
    *
    * @returns status: 0: OK, 1: disk not initialized, 2: no medium in the drive, 4: write protected
    */
    virtual int disk_status() = 0;

    /*
    * Get string product descriptor
    *
    * @returns pointer to the string product descriptor
    */
    virtual const uint8_t *stringIproductDesc();

    /*
    * Get string interface descriptor
    *
    * @returns pointer to the string interface descriptor
    */
    virtual const uint8_t *stringIinterfaceDesc();

    /*
    * Get configuration descriptor
    *
    * @returns pointer to the configuration descriptor
    */
    virtual const uint8_t *configurationDesc();

    /*
    * Callback called when a packet is received
    */
    virtual bool EP2_OUT_callback();

    /*
    * Callback called when a packet has been sent
    */
    virtual bool EP2_IN_callback();

    /*
    * Set configuration of device. Add endpoints
    */
    virtual bool USBCallback_setConfiguration(uint8_t configuration);

    /*
    * Callback called to process class specific requests
    */
    virtual bool USBCallback_request();


private:

    // MSC Bulk-only Stage
    enum Stage {
        READ_CBW,     // wait a CBW
        ERROR,        // error
        PROCESS_CBW,  // process a CBW request
        SEND_CSW,     // send a CSW
        WAIT_CSW,     // wait that a CSW has been effectively sent
    };

    // Bulk-only CBW
    typedef struct {
        uint32_t Signature;
        uint32_t Tag;
        uint32_t DataLength;
        uint8_t  Flags;
        uint8_t  LUN;
        uint8_t  CBLength;
        uint8_t  CB[16];
    } PACKED CBW;

    // Bulk-only CSW
    typedef struct {
        uint32_t Signature;
        uint32_t Tag;
        uint32_t DataResidue;
        uint8_t  Status;
    } PACKED CSW;

    //state of the bulk-only state machine
    Stage stage;

    // current CBW
    CBW cbw;

    // CSW which will be sent
    CSW csw;

    // addr where will be read or written data
    uint32_t addr;

    // length of a reading or writing
    uint32_t length;

    // memory OK (after a memoryVerify)
    bool memOK;

    // cache in RAM before writing in memory. Useful also to read a block.
    uint8_t * page;

    int BlockSize;
    uint64_t MemorySize;
    uint64_t BlockCount;

    void CBWDecode(uint8_t * buf, uint16_t size);
    void sendCSW (void);
    bool inquiryRequest (void);
    bool write (uint8_t * buf, uint16_t size);
    bool readFormatCapacity();
    bool readCapacity (void);
    bool infoTransfer (void);
    void memoryRead (void);
    bool modeSense6 (void);
    void testUnitReady (void);
    bool requestSense (void);
    void memoryVerify (uint8_t * buf, uint16_t size);
    void memoryWrite (uint8_t * buf, uint16_t size);
    void reset();
    void fail();
};

#endif