mbv: now with DDR! and a wozmon

We have access to 256 MiB of fresh DDR3.
Isn't that great?

prog.py is a bit opinionated for now:
- tty is /dev/ttyUSB1
- writing programs to DDR

mbv/apps/fromddr.ld

@@ -0,0 +1,43 @@
+MEMORY
+{
+/*    RAM (rwx) : ORIGIN = 0x00000800, LENGTH = 14336 */
+    RAM (rwx) : ORIGIN = 0x80000000, LENGTH = 0x10000000
+}
+
+_vector_table = 0x0;
+
+SECTIONS
+{
+    .text :
+    {
+        _text_begin = .;
+        KEEP(*(.start))
+
+        *(.text*)
+        _text_end = .;
+
+        *(.rodata*)
+    } > RAM
+
+    .bss (NOLOAD) :
+    {
+        _bss_begin = .;
+        *(.bss*)
+        *(COMMON)
+        _bss_end = .;
+    } > RAM
+
+    .data :
+    {
+        *(.data*)
+
+        __exidx_start = .;
+        *(.exidx*)
+        __exidx_end = .;
+    } > RAM
+
+    _heap_begin = .;
+
+    _initial_stack_pointer = 16384;
+    _heap_end = _initial_stack_pointer - 1024;
+}

mbv/apps/wozmon/wozmon.cc

@@ -0,0 +1,169 @@
+#include <cstdint>
+
+#include "xuartlite.h"
+
+struct Gpio {
+    volatile uint32_t data;
+};
+
+#define gpio0 ((Gpio*)0x40000000)
+
+namespace {
+constexpr uintptr_t kUart0BaseAddress = 0x40600000;
+XUartLite uart0_inst;
+XUartLite_Config uart0_config = {
+    .DeviceId = 0,
+    .RegBaseAddr = kUart0BaseAddress,
+    .BaudRate = 115200,
+    .UseParity = false,
+    .DataBits = 8,
+};
+
+XUartLite* uart0 = &uart0_inst;
+
+void InitUarts() {
+    XUartLite_CfgInitialize(uart0, &uart0_config, uart0_config.RegBaseAddr);
+}
+
+uint8_t UartRead() {
+    uint8_t c;
+    while (XUartLite_Recv(uart0, &c, 1) < 1) {
+    }
+    return c;
+}
+
+void UartWrite(uint8_t c) {
+    XUartLite_Send(uart0, &c, 1);
+    while (XUartLite_IsSending(uart0)) {}
+}
+
+void Jump(uint32_t addr) {
+    auto jump = reinterpret_cast<void (*)()>(addr);
+    jump();
+}
+
+constexpr uint8_t kBackspace = 0x7f;
+constexpr uint8_t kOtherBackspace = 0x08;
+
+uint8_t ReadHexNibble(uint8_t c) {
+    // lowercase only
+    if (c <= '9') {
+        return c - '0';
+    }
+    return 10 + (c - 'a');
+}
+
+uint32_t ReadHex(const char* buf) {
+    uint32_t out = 0;
+    while (*buf == ' ') {
+        buf++;
+    }
+    for (int i = 0; i < 8; i++) {
+        uint8_t c = ReadHexNibble(*buf);
+        if (c > 0xf) {
+            break;
+        }
+        out = (out << 4) + c;
+        buf++;
+    }
+
+    return out;
+}
+
+void WriteHexNibble(uint8_t c) {
+    if (c > 9) {
+        UartWrite('a' + c - 10);
+    } else {
+        UartWrite('0' + c);
+    }
+}
+
+void UartWriteUint32(uint32_t a) {
+    for (int i = 0; i < 8; i++) {
+        WriteHexNibble((a >> 28) & 0xf);
+        a <<= 4;
+    }
+}
+
+void UartWriteUint8(uint8_t a) {
+    WriteHexNibble(a >> 4);
+    WriteHexNibble(a & 0xf);
+}
+
+void UartDump(uint32_t addr, int count) {
+   for (int i = 0; i < count; i++) {
+       UartWrite(' ');
+       UartWriteUint8(*reinterpret_cast<uint8_t*>(addr + i));
+   } 
+}
+
+void DumpHex(uint32_t addr) {
+    addr &= 0xfffffffc;
+    UartWriteUint32(addr);
+    UartWrite(':');
+    UartDump(addr, 4);
+    UartWrite('\r');
+    UartWrite('\n');
+}
+
+int FindChar(const char* buf, uint8_t c) {
+    int found = 0;
+    while (*buf) {
+        if (*buf == c) {
+            return found;
+        }
+        found++;
+        buf++;
+    }
+    return -1;
+}
+
+
+}  // namespace
+
+int main() {
+    gpio0->data = 1;
+    uint32_t cur_addr = 0;
+    uint32_t cur_data = 0;
+    bool writing = false;
+
+    char inbuf[64] = {};
+    char* inptr = inbuf;
+
+    InitUarts();
+
+    while (1) {
+        uint8_t c = UartRead();
+        UartWrite(c); // echo
+        if (c == '\r') {
+            gpio0->data = 0x55;
+            *inptr = 0;
+            if (inptr == inbuf) {
+                cur_addr += 4;
+            } else if (FindChar(inbuf, 'r') >= 0) {
+                Jump(cur_addr);
+            } else {
+                cur_addr = ReadHex(inbuf);
+                UartWrite('\n');
+            }
+            DumpHex(cur_addr);
+            int assigned = FindChar(inbuf, ':');
+            if (assigned >= 0) {
+                cur_data = ReadHex(inbuf + assigned + 1);
+                *(reinterpret_cast<uint32_t*>(cur_addr)) = cur_data;
+            }
+            inptr = inbuf;
+        } else if (c == kBackspace) {
+            inptr--;
+            if (inptr < inbuf) {
+                inptr = inbuf;
+                continue;
+            }
+            UartWrite(kOtherBackspace);
+            UartWrite(' ');
+            UartWrite(kOtherBackspace);
+        } else {
+            *inptr++ = c;
+        }
+    }
+}