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

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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!

USBDevice/USBHAL_STM32F4.cpp

Committer:
mbed_official
Date:
2014-06-03
Revision:
25:7c72828865f3
Parent:
16:4f6df64750bd

File content as of revision 25:7c72828865f3:

/* 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.
*/

#if defined(TARGET_STM32F4XX)

#include "USBHAL.h"
#include "USBRegs_STM32.h"
#include "pinmap.h"

USBHAL * USBHAL::instance;

static volatile int epComplete = 0;

static uint32_t bufferEnd = 0;
static const uint32_t rxFifoSize = 512;
static uint32_t rxFifoCount = 0;

static uint32_t setupBuffer[MAX_PACKET_SIZE_EP0 >> 2];

uint32_t USBHAL::endpointReadcore(uint8_t endpoint, uint8_t *buffer) {
    return 0;
}

USBHAL::USBHAL(void) {
    NVIC_DisableIRQ(OTG_FS_IRQn);
    epCallback[0] = &USBHAL::EP1_OUT_callback;
    epCallback[1] = &USBHAL::EP1_IN_callback;
    epCallback[2] = &USBHAL::EP2_OUT_callback;
    epCallback[3] = &USBHAL::EP2_IN_callback;
    epCallback[4] = &USBHAL::EP3_OUT_callback;
    epCallback[5] = &USBHAL::EP3_IN_callback;

    // Enable power and clocking
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;

    pin_function(PA_8, STM_PIN_DATA(2, 10));
    pin_function(PA_9, STM_PIN_DATA(0, 0));
    pin_function(PA_10, STM_PIN_DATA(2, 10));
    pin_function(PA_11, STM_PIN_DATA(2, 10));
    pin_function(PA_12, STM_PIN_DATA(2, 10));

    // Set ID pin to open drain with pull-up resistor
    pin_mode(PA_10, OpenDrain);
    GPIOA->PUPDR &= ~(0x3 << 20);
    GPIOA->PUPDR |= 1 << 20;

    // Set VBUS pin to open drain
    pin_mode(PA_9, OpenDrain);

    RCC->AHB2ENR |= RCC_AHB2ENR_OTGFSEN;

    // Enable interrupts
    OTG_FS->GREGS.GAHBCFG |= (1 << 0);

    // Turnaround time to maximum value - too small causes packet loss
    OTG_FS->GREGS.GUSBCFG |= (0xF << 10);

    // Unmask global interrupts
    OTG_FS->GREGS.GINTMSK |= (1 << 3) | // SOF
                             (1 << 4) | // RX FIFO not empty
                             (1 << 12); // USB reset

    OTG_FS->DREGS.DCFG |= (0x3 << 0) | // Full speed
                          (1 << 2); // Non-zero-length status OUT handshake

    OTG_FS->GREGS.GCCFG |= (1 << 19) | // Enable VBUS sensing
                           (1 << 16); // Power Up

    instance = this;
    NVIC_SetVector(OTG_FS_IRQn, (uint32_t)&_usbisr);
    NVIC_SetPriority(OTG_FS_IRQn, 1);
}

USBHAL::~USBHAL(void) {
}

void USBHAL::connect(void) {
    NVIC_EnableIRQ(OTG_FS_IRQn);
}

void USBHAL::disconnect(void) {
    NVIC_DisableIRQ(OTG_FS_IRQn);
}

void USBHAL::configureDevice(void) {
    // Not needed
}

void USBHAL::unconfigureDevice(void) {
    // Not needed
}

void USBHAL::setAddress(uint8_t address) {
    OTG_FS->DREGS.DCFG |= (address << 4);
    EP0write(0, 0);
}

bool USBHAL::realiseEndpoint(uint8_t endpoint, uint32_t maxPacket,
                             uint32_t flags) {
    uint32_t epIndex = endpoint >> 1;

    uint32_t type;
    switch (endpoint) {
        case EP0IN:
        case EP0OUT:
            type = 0;
            break;
        case EPISO_IN:
        case EPISO_OUT:
            type = 1;
        case EPBULK_IN:
        case EPBULK_OUT:
            type = 2;
            break;
        case EPINT_IN:
        case EPINT_OUT:
            type = 3;
            break;
    }

    // Generic in or out EP controls
    uint32_t control = (maxPacket << 0) | // Packet size
                       (1 << 15) | // Active endpoint
                       (type << 18); // Endpoint type

    if (endpoint & 0x1) { // In Endpoint
        // Set up the Tx FIFO
        if (endpoint == EP0IN) {
            OTG_FS->GREGS.DIEPTXF0_HNPTXFSIZ = ((maxPacket >> 2) << 16) |
                                               (bufferEnd << 0);
        }
        else {
            OTG_FS->GREGS.DIEPTXF[epIndex - 1] = ((maxPacket >> 2) << 16) |
                                                 (bufferEnd << 0);
        }
        bufferEnd += maxPacket >> 2;

        // Set the In EP specific control settings
        if (endpoint != EP0IN) {
            control |= (1 << 28); // SD0PID
        }

        control |= (epIndex << 22) | // TxFIFO index
                   (1 << 27); // SNAK
        OTG_FS->INEP_REGS[epIndex].DIEPCTL = control;

        // Unmask the interrupt
        OTG_FS->DREGS.DAINTMSK |= (1 << epIndex);
    }
    else { // Out endpoint
        // Set the out EP specific control settings
        control |= (1 << 26); // CNAK
        OTG_FS->OUTEP_REGS[epIndex].DOEPCTL = control;

        // Unmask the interrupt
        OTG_FS->DREGS.DAINTMSK |= (1 << (epIndex + 16));
    }
    return true;
}

// read setup packet
void USBHAL::EP0setup(uint8_t *buffer) {
    memcpy(buffer, setupBuffer, MAX_PACKET_SIZE_EP0);
}

void USBHAL::EP0readStage(void) {
}

void USBHAL::EP0read(void) {
}

uint32_t USBHAL::EP0getReadResult(uint8_t *buffer) {
    uint32_t* buffer32 = (uint32_t *) buffer;
    uint32_t length = rxFifoCount;
    for (uint32_t i = 0; i < length; i += 4) {
        buffer32[i >> 2] = OTG_FS->FIFO[0][0];
    }

    rxFifoCount = 0;
    return length;
}

void USBHAL::EP0write(uint8_t *buffer, uint32_t size) {
    endpointWrite(0, buffer, size);
}

void USBHAL::EP0getWriteResult(void) {
}

void USBHAL::EP0stall(void) {
    // If we stall the out endpoint here then we have problems transferring
    // and setup requests after the (stalled) get device qualifier requests.
    // TODO: Find out if this is correct behavior, or whether we are doing
    // something else wrong
    stallEndpoint(EP0IN);
//    stallEndpoint(EP0OUT);
}

EP_STATUS USBHAL::endpointRead(uint8_t endpoint, uint32_t maximumSize) {
    uint32_t epIndex = endpoint >> 1;
    uint32_t size = (1 << 19) | // 1 packet
                    (maximumSize << 0); // Packet size
//    if (endpoint == EP0OUT) {
        size |= (1 << 29); // 1 setup packet
//    }
    OTG_FS->OUTEP_REGS[epIndex].DOEPTSIZ = size;
    OTG_FS->OUTEP_REGS[epIndex].DOEPCTL |= (1 << 31) | // Enable endpoint
                                           (1 << 26); // Clear NAK

    epComplete &= ~(1 << endpoint);
    return EP_PENDING;
}

EP_STATUS USBHAL::endpointReadResult(uint8_t endpoint, uint8_t * buffer, uint32_t *bytesRead) {
    if (!(epComplete & (1 << endpoint))) {
        return EP_PENDING;
    }

    uint32_t* buffer32 = (uint32_t *) buffer;
    uint32_t length = rxFifoCount;
    for (uint32_t i = 0; i < length; i += 4) {
        buffer32[i >> 2] = OTG_FS->FIFO[endpoint >> 1][0];
    }
    rxFifoCount = 0;
    *bytesRead = length;
    return EP_COMPLETED;
}

EP_STATUS USBHAL::endpointWrite(uint8_t endpoint, uint8_t *data, uint32_t size) {
    uint32_t epIndex = endpoint >> 1;
    OTG_FS->INEP_REGS[epIndex].DIEPTSIZ = (1 << 19) | // 1 packet
                                          (size << 0); // Size of packet
    OTG_FS->INEP_REGS[epIndex].DIEPCTL |= (1 << 31) | // Enable endpoint
                                          (1 << 26); // CNAK
    OTG_FS->DREGS.DIEPEMPMSK = (1 << epIndex);

    while ((OTG_FS->INEP_REGS[epIndex].DTXFSTS & 0XFFFF) < ((size + 3) >> 2));

    for (uint32_t i=0; i<(size + 3) >> 2; i++, data+=4) {
        OTG_FS->FIFO[epIndex][0] = *(uint32_t *)data;
    }

    epComplete &= ~(1 << endpoint);

    return EP_PENDING;
}

EP_STATUS USBHAL::endpointWriteResult(uint8_t endpoint) {
    if (epComplete & (1 << endpoint)) {
        epComplete &= ~(1 << endpoint);
        return EP_COMPLETED;
    }

    return EP_PENDING;
}

void USBHAL::stallEndpoint(uint8_t endpoint) {
    if (endpoint & 0x1) { // In EP
        OTG_FS->INEP_REGS[endpoint >> 1].DIEPCTL |= (1 << 30) | // Disable
                                                    (1 << 21); // Stall
    }
    else {  // Out EP
        OTG_FS->DREGS.DCTL |= (1 << 9); // Set global out NAK
        OTG_FS->OUTEP_REGS[endpoint >> 1].DOEPCTL |= (1 << 30) | // Disable
                                                     (1 << 21); // Stall
    }
}

void USBHAL::unstallEndpoint(uint8_t endpoint) {

}

bool USBHAL::getEndpointStallState(uint8_t endpoint) {
    return false;
}

void USBHAL::remoteWakeup(void) {
}


void USBHAL::_usbisr(void) {
    instance->usbisr();
}


void USBHAL::usbisr(void) {
    if (OTG_FS->GREGS.GINTSTS & (1 << 12)) { // USB Reset
        // Set SNAK bits
        OTG_FS->OUTEP_REGS[0].DOEPCTL |= (1 << 27);
        OTG_FS->OUTEP_REGS[1].DOEPCTL |= (1 << 27);
        OTG_FS->OUTEP_REGS[2].DOEPCTL |= (1 << 27);
        OTG_FS->OUTEP_REGS[3].DOEPCTL |= (1 << 27);

        OTG_FS->DREGS.DIEPMSK = (1 << 0);

        bufferEnd = 0;

        // Set the receive FIFO size
        OTG_FS->GREGS.GRXFSIZ = rxFifoSize >> 2;
        bufferEnd += rxFifoSize >> 2;

        // Create the endpoints, and wait for setup packets on out EP0
        realiseEndpoint(EP0IN, MAX_PACKET_SIZE_EP0, 0);
        realiseEndpoint(EP0OUT, MAX_PACKET_SIZE_EP0, 0);
        endpointRead(EP0OUT, MAX_PACKET_SIZE_EP0);

        OTG_FS->GREGS.GINTSTS = (1 << 12);
    }

    if (OTG_FS->GREGS.GINTSTS & (1 << 4)) { // RX FIFO not empty
        uint32_t status = OTG_FS->GREGS.GRXSTSP;

        uint32_t endpoint = (status & 0xF) << 1;
        uint32_t length = (status >> 4) & 0x7FF;
        uint32_t type = (status >> 17) & 0xF;

        rxFifoCount = length;

        if (type == 0x6) {
            // Setup packet
            for (uint32_t i=0; i<length; i+=4) {
                setupBuffer[i >> 2] = OTG_FS->FIFO[0][i >> 2];
            }
            rxFifoCount = 0;
        }

        if (type == 0x4) {
            // Setup complete
            EP0setupCallback();
            endpointRead(EP0OUT, MAX_PACKET_SIZE_EP0);
        }

        if (type == 0x2) {
            // Out packet
            if (endpoint == EP0OUT) {
                EP0out();
            }
            else {
                epComplete |= (1 << endpoint);
                if ((instance->*(epCallback[endpoint - 2]))()) {
                    epComplete &= (1 << endpoint);
                }
            }
        }

        for (uint32_t i=0; i<rxFifoCount; i+=4) {
            (void) OTG_FS->FIFO[0][0];
        }
        OTG_FS->GREGS.GINTSTS = (1 << 4);
    }

    if (OTG_FS->GREGS.GINTSTS & (1 << 18)) { // In endpoint interrupt
        // Loop through the in endpoints
        for (uint32_t i=0; i<4; i++) {
            if (OTG_FS->DREGS.DAINT & (1 << i)) { // Interrupt is on endpoint

                if (OTG_FS->INEP_REGS[i].DIEPINT & (1 << 7)) {// Tx FIFO empty
                    // If the Tx FIFO is empty on EP0 we need to send a further
                    // packet, so call EP0in()
                    if (i == 0) {
                        EP0in();
                    }
                    // Clear the interrupt
                    OTG_FS->INEP_REGS[i].DIEPINT = (1 << 7);
                    // Stop firing Tx empty interrupts
                    // Will get turned on again if another write is called
                    OTG_FS->DREGS.DIEPEMPMSK &= ~(1 << i);
                }

                // If the transfer is complete
                if (OTG_FS->INEP_REGS[i].DIEPINT & (1 << 0)) { // Tx Complete
                    epComplete |= (1 << (1 + (i << 1)));
                    OTG_FS->INEP_REGS[i].DIEPINT = (1 << 0);
                }
            }
        }
        OTG_FS->GREGS.GINTSTS = (1 << 18);
    }

    if (OTG_FS->GREGS.GINTSTS & (1 << 3)) { // Start of frame
        SOF((OTG_FS->GREGS.GRXSTSR >> 17) & 0xF);
        OTG_FS->GREGS.GINTSTS = (1 << 3);
    }
}


#endif