Add untested code to write RTC on EDX7

Author: rasky

src/joybus_rtc.c

@@ -10,6 +10,8 @@
 #include "joybus_rtc.h"
 #include "libcart/cart.h"
 #include "n64sys.h"
+#include "dma.h"
+#include "utils.h"
 #include "rtc_internal.h"
 #include "rtc_internal.h"
 
@@ -424,6 +426,97 @@ int joybus_rtc_get_time( time_t *out )
     return RTC_ESUCCESS;
 }
 
+static const uint32_t ED64X_REG_I2C_CMD = 0x1F800018;
+static const uint32_t ED64X_REG_I2C_DAT = 0x1F80001C;
+
+static int ed64x_i2c_status(void)
+{
+    return io_read(ED64X_REG_I2C_CMD) & 1;
+}
+
+static int ed64x_i2c_cmd(uint8_t cmd)
+{
+    io_write(ED64X_REG_I2C_DAT, cmd);
+    while (io_read(ED64X_REG_I2C_CMD) & 0x80) {}
+    return ed64x_i2c_status();
+}
+
+static uint8_t ed64x_i2c_dat(uint8_t cmd)
+{
+    io_write(ED64X_REG_I2C_DAT, cmd);
+    while (io_read(ED64X_REG_I2C_CMD) & 0x80) {}
+    return io_read(ED64X_REG_I2C_DAT);
+}
+
+static void ed64x_i2c_start(void)
+{
+    uint8_t val = io_read(ED64X_REG_I2C_CMD);
+    io_write(ED64X_REG_I2C_CMD, 0x20);
+    io_write(ED64X_REG_I2C_DAT, 0xFF);
+    while (io_read(ED64X_REG_I2C_CMD) & 0x80) {}
+    io_write(ED64X_REG_I2C_CMD, val | 0x11); // set write mode
+}
+
+static void ed64x_i2c_end(void)
+{
+    io_write(ED64X_REG_I2C_CMD, 0x30);
+    io_write(ED64X_REG_I2C_DAT, 0xFF);
+    while (io_read(ED64X_REG_I2C_CMD) & 0x80) {}
+}
+
+static void ed64x_i2c_setwr(void)
+{
+    io_write(ED64X_REG_I2C_CMD, io_read(ED64X_REG_I2C_CMD) | 0x11);
+}
+
+static void ed64x_i2c_setrd(void)
+{
+    io_write(ED64X_REG_I2C_CMD, io_read(ED64X_REG_I2C_CMD) | 0x10);
+}
+
+static int ed64x_i2c_write(uint16_t addr, const uint8_t* data, int len)
+{
+    uint8_t bus_addr = addr >> 8;
+    uint8_t dev_addr = addr & 0xFF;
+
+    for (int i=0; i<len; i+=8) {
+        int retry = 0;
+        while (1) {
+            ed64x_i2c_start();
+            if (ed64x_i2c_cmd(bus_addr) == 0)
+                break;
+            ed64x_i2c_end();
+            if (++retry == 16)
+                return -1;
+        }
+        ed64x_i2c_cmd(dev_addr+i);
+        for (int j=0; j<MIN(len, 8); j++) {
+            io_write(ED64X_REG_I2C_DAT, data[i+j]);
+            while (io_read(ED64X_REG_I2C_CMD) & 0x80) {}
+        }
+        ed64x_i2c_end();
+    }
+    return 0;
+}
+
+static void ed64x_rtc_write( time_t new_time )
+{
+    struct tm * rtc_time = gmtime( &new_time );
+    uint8_t buf[7];
+
+    // The RTC is a DS1337. Encode time according to its datasheet
+    enum { DS1337_BUS_ADDR = 0xD000 };
+
+    buf[0] = bcd_encode( rtc_time->tm_sec );
+    buf[1] = bcd_encode( rtc_time->tm_min );
+    buf[2] = bcd_encode( rtc_time->tm_hour );  // bit 6 toggles 12/24 hour mode
+    buf[3] = bcd_encode( rtc_time->tm_wday + 1 );
+    buf[4] = bcd_encode( rtc_time->tm_mday );
+    buf[5] = bcd_encode( rtc_time->tm_mon + 1 ); // bit 7 is the century bit
+    buf[6] = bcd_encode( rtc_time->tm_year % 100 );
+    ed64x_i2c_write( DS1337_BUS_ADDR + 0, buf, sizeof(buf) );
+}
+
 int joybus_rtc_set_time( time_t new_time )
 {
     if( new_time < JOYBUS_RTC_TIMESTAMP_MIN || new_time > JOYBUS_RTC_TIMESTAMP_MAX )