mbv: debugging the async app

mbv/apps/async/main.cc

@@ -63,9 +63,6 @@ async::task<> echo() {
 
 }  // namespace
 
-#define XUL_SR_RX_FIFO_FULL 0x02       /* receive FIFO full */
-#define XUL_SR_RX_FIFO_VALID_DATA 0x01 /* data in receive FIFO */
-
 int main() {
     SetupUart();
     UartWriteCrash("uart setup done\r\n");
@@ -99,10 +96,6 @@ int main() {
 #include "itoa.h"
 #include "lock.h"
 
-#ifndef SBRK_STATS
-#define SBRK_STATS 0
-#endif
-
 extern unsigned char _heap_begin, _heap_end;
 
 extern "C" void* _sbrk(int increment) {

mbv/apps/async/main2.cc

@@ -0,0 +1,108 @@
+#include "buffer.h"
+#include "gpio.h"
+#include "intc.h"
+#include "interrupts.h"
+#include "pol0.h"
+#include "timer.h"
+#include "trace.h"
+#include "uart2.h"
+
+namespace {
+
+Timer* timer0;
+
+void Uart0Isr() {
+//    ToggleLed(7);
+    HandleUartIsr();
+}
+
+void Timer0Isr() {
+    SetLed(6);
+    __builtin_trap();
+}
+
+void SetupUart() {
+    InitUarts();
+
+    intc::SetIsr(UART0_IRQN, Uart0Isr);
+    intc::SetIrqEnabled(UART0_IRQN, true);
+}
+
+void SetupTimer() {
+    timer0 = Timer::Instance(TIMER0_BASE);
+//    timer0->SetupAsWdt(100'000 * 1000);
+    timer0->EnableT1();
+
+    intc::SetIsr(TIMER0_IRQN, Timer0Isr);
+    intc::SetIrqEnabled(TIMER0_IRQN, true);
+}
+
+void SetupInterrupts() {
+    intc::EnableInterrupts();
+    SetExternalInterruptHandler(intc::InterruptHandler);
+    EnableExternalInterrupts();
+    EnableInterrupts(true);
+}
+
+}  // namespace
+
+int main() {
+    SetupUart();
+    UartWriteCrash("uart setup done\r\n");
+    SetupTimer();
+    UartWriteCrash("timer setup done\r\n");
+
+    SetupInterrupts();
+
+    UartWriteCrash("init done. starting main loop\r\n");
+
+    UartEcho();
+
+    // should never get here
+}
+
+/// stdlib stuff
+
+#include <sys/time.h>
+
+#include <cstdint>
+
+#include "itoa.h"
+#include "lock.h"
+
+extern unsigned char _heap_begin, _heap_end;
+
+extern "C" void* _sbrk(int increment) {
+    static unsigned char* heap = &_heap_begin;
+    unsigned char* prev_heap = heap;
+    if (heap + increment >= &_heap_end) {
+        UartWriteCrash("Heap overflow!\r\n");
+        return reinterpret_cast<void*>(-1);
+    }
+    heap += increment;
+    return prev_heap;
+}
+
+extern "C" int _gettimeofday(struct timeval* tv, void* tzvp) {
+    (void)tzvp;
+    uint32_t ticks = timer0->GetT1Ticks();
+    tv->tv_sec = ticks / 100000000;
+    tv->tv_usec = (ticks % 100000000) / 100;
+
+    return 0;
+}
+
+extern "C" uint8_t __atomic_exchange_1(volatile void* ptr, uint8_t val,
+                                       int memorder) {
+    (void)memorder;
+    auto* dest = reinterpret_cast<volatile uint8_t*>(ptr);
+    bool ret;
+
+    {
+        InterruptLock lock;
+        ret = *dest;
+        *dest = val;
+    }
+
+    return ret;
+}

mbv/apps/async/ring_buffer.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <atomic>
 #include <span>
 
 #include "lock.h"
@@ -8,9 +7,9 @@
 struct RingBuffer {
     std::span<std::byte> buffer;
 
-    std::atomic<size_t> read_ptr = 0;
-    std::atomic<size_t> write_ptr = 0;
-    std::atomic<bool> full = 0;
+    size_t read_ptr = 0;
+    size_t write_ptr = 0;
+    size_t used = 0;
 
     bool Store(std::span<const std::byte> data) {
         InterruptLock lock;
@@ -53,9 +52,7 @@ struct RingBuffer {
             return false;
         }
         write_ptr = (write_ptr + amount) % buffer.size();
-        if (read_ptr == write_ptr) {
-            full = true;
-        }
+        used = used + amount;
         return true;
     }
 
@@ -66,25 +63,20 @@ struct RingBuffer {
             return false;
         }
         read_ptr = (read_ptr + amount) % buffer.size();
-        if (amount > 0) {
-            full = false;
-        }
+        used = used - amount;
         return true;
     }
 
     size_t FreeSpace() const {
         InterruptLock lock;
 
-        return buffer.size() - AvailableData();
+        return buffer.size() - used;
     }
 
     size_t AvailableData() const {
         InterruptLock lock;
 
-        if (read_ptr == write_ptr) {
-            return full ? buffer.size() : 0;
-        }
-        return (buffer.size() + write_ptr - read_ptr) % buffer.size();
+        return used;
     }
 
     uint8_t* RawReadPointer() const {
@@ -93,16 +85,21 @@ struct RingBuffer {
         return reinterpret_cast<uint8_t*>(buffer.data() + read_ptr);
     }
 
+    uint8_t* RawWritePointer() const {
+        InterruptLock lock;
+
+        return reinterpret_cast<uint8_t*>(buffer.data() + write_ptr);
+    }
+
+    size_t ContiguousFreeSpace() const {
+        InterruptLock lock;
+
+        return std::min(FreeSpace(), buffer.size() - write_ptr);
+    }
+
     size_t ContiguousAvailableData() const {
         InterruptLock lock;
 
-        if (read_ptr < write_ptr) {
-            return AvailableData();
-        }
-        if (full) {
-            return 0;
-        }
-
-        return buffer.size() - read_ptr;
+        return std::min(AvailableData(), buffer.size() - read_ptr);
     }
 };

mbv/apps/async/uart.cc

@@ -27,6 +27,8 @@ std::array<std::byte, kUartTxBufferSize> tx_buffer = {};
 RingBuffer tx_ring_buffer{.buffer = tx_buffer};
 
 XUartLite* uart0 = &uart0_inst;
+
+bool sending;
 }  // namespace
 
 void InitUarts() {
@@ -35,9 +37,12 @@ void InitUarts() {
     XUartLite_SetSendHandler(uart0, HandleUartTxFromIsr, nullptr);
     XUartLite_SetRecvHandler(uart0, HandleUartRxFromIsr, nullptr);
     XUartLite_EnableInterrupt(uart0);
+
+    sending = false;
 }
 
 void UartWriteCrash(std::span<const std::byte> data) {
+    XUartLite_DisableInterrupt(uart0);
     while (data.size() > 0) {
         while (XUartLite_IsSending(uart0)) {
         }
@@ -48,6 +53,7 @@ void UartWriteCrash(std::span<const std::byte> data) {
     }
     while (XUartLite_IsSending(uart0)) {
     }
+    XUartLite_EnableInterrupt(uart0);
 }
 
 async::task<> UartWrite(std::span<const std::byte> data) {
@@ -79,10 +85,11 @@ async::task<> UartWriteLoop(
 
         {
             InterruptLock lock;
-            if (!XUartLite_IsSending(uart0)) {
+            if (!sending) {
                 tracing::trace(tracing::TraceEvent::kUartSend);
                 XUartLite_Send(uart0, tx_ring_buffer.RawReadPointer(),
                                tx_ring_buffer.ContiguousAvailableData());
+                sending = true;
             }
         }
     }
@@ -139,11 +146,13 @@ async::task<buffer> UartRead(int size) {
 }
 
 void HandleUartTxFromIsr(void*, unsigned int transmitted) {
+    sending = false;
     tx_ring_buffer.Pop(transmitted);
     if (tx_ring_buffer.AvailableData() > 0) {
         tracing::trace(tracing::TraceEvent::kUartSend);
         XUartLite_Send(uart0, tx_ring_buffer.RawReadPointer(),
                        tx_ring_buffer.ContiguousAvailableData());
+        sending = true;
     }
     async::resume(AwaitableType::kUartTx);
 }

mbv/apps/async/uart2.cc

@@ -0,0 +1,119 @@
+#include "uart2.h"
+
+#include "gpio.h"
+#include "lock.h"
+#include "pol0.h"
+#include "ring_buffer.h"
+#include "xuartlite.h"
+
+namespace {
+
+constexpr uintptr_t kUart0BaseAddress = UART0_BASE;
+XUartLite uart0_inst;
+XUartLite_Config uart0_config = {
+    .DeviceId = 0,
+    .RegBaseAddr = kUart0BaseAddress,
+    .BaudRate = 115200,
+    .UseParity = false,
+    .DataBits = 8,
+};
+
+constexpr size_t kUartRxBufferSize = 256;
+std::array<std::byte, kUartRxBufferSize> rx_buffer = {};
+RingBuffer rx_ring_buffer{.buffer = rx_buffer};
+
+constexpr size_t kUartTxBufferSize = 256;
+std::array<std::byte, kUartTxBufferSize> tx_buffer = {};
+RingBuffer tx_ring_buffer{.buffer = tx_buffer};
+
+XUartLite* uart0 = &uart0_inst;
+
+volatile int sending = 0;
+
+void StartReceiving() {
+    while (1) {
+        if (rx_ring_buffer.FreeSpace() < 1) {
+            // woops, full. discard some data
+            // TODO: keep track of overrun stats
+            rx_ring_buffer.Pop(1);
+        }
+        if (XUartLite_Recv(uart0, rx_ring_buffer.RawWritePointer(), 1) < 1) {
+            break;
+        }
+        rx_ring_buffer.Push(1);
+    }
+}
+
+void StartSending() {
+    if (tx_ring_buffer.AvailableData() > 0 && sending < 1) {
+        sending += 1;
+        XUartLite_Send(uart0, tx_ring_buffer.RawReadPointer(), 1);
+    }
+}
+
+std::byte UartReadByte() {
+    std::byte c;
+    while (!rx_ring_buffer.Load(std::span{&c, 1})) {
+    }
+
+    return c;
+}
+
+void UartWriteByte(std::byte c) {
+    while (!tx_ring_buffer.Store(std::span{&c, 1})) {
+    }
+    {
+        InterruptLock lock;
+        StartSending();
+    }
+}
+
+}  // namespace
+
+void InitUarts() {
+    XUartLite_CfgInitialize(uart0, &uart0_config, uart0_config.RegBaseAddr);
+
+    XUartLite_SetSendHandler(uart0, HandleUartTxFromIsr, nullptr);
+    XUartLite_SetRecvHandler(uart0, HandleUartRxFromIsr, nullptr);
+    StartReceiving();
+    XUartLite_EnableInterrupt(uart0);
+}
+
+void UartWriteCrash(std::span<const std::byte> data) {
+    XUartLite_DisableInterrupt(uart0);
+    while (data.size() > 0) {
+        while (XUartLite_IsSending(uart0)) {
+        }
+        auto* dat =
+            reinterpret_cast<uint8_t*>(const_cast<std::byte*>(data.data()));
+        uint8_t sent = XUartLite_Send(uart0, dat, data.size());
+        data = data.subspan(sent);
+    }
+    while (XUartLite_IsSending(uart0)) {
+    }
+    XUartLite_EnableInterrupt(uart0);
+}
+
+void UartEcho() {
+    while (1) {
+        gpio0->data = tx_ring_buffer.AvailableData();
+
+        std::byte c = UartReadByte();
+        UartWriteByte(c);
+
+        //gpio0->data = uart0->Stats.ReceiveOverrunErrors;
+    }
+}
+
+void HandleUartTxFromIsr(void*, unsigned int transmitted) {
+    sending -= 1;
+    tx_ring_buffer.Pop(transmitted);
+    StartSending();
+}
+
+void HandleUartRxFromIsr(void*, unsigned int transmitted) {
+    rx_ring_buffer.Push(transmitted);
+    StartReceiving();
+}
+
+void HandleUartIsr() { XUartLite_InterruptHandler(uart0); }

mbv/apps/async/uart2.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <span>
+#include <string_view>
+
+void InitUarts();
+
+// send and poll the uart until transmitted
+void UartWriteCrash(std::span<const std::byte> data);
+inline void UartWriteCrash(std::string_view s) {
+    return UartWriteCrash(std::as_bytes(std::span{s.data(), s.size()}));
+}
+
+void UartEcho();
+
+void HandleUartTxFromIsr(void*, unsigned int transmitted);
+void HandleUartRxFromIsr(void*, unsigned int);
+void HandleUartIsr();