made the SPI_CD_* commands set the correct GD-ROM state

src/guest/bios/bios.c

@@ -388,6 +388,8 @@ int bios_invalid_instr(struct bios *bios) {
   struct sh4_context *ctx = &dc->sh4->ctx;
   uint32_t pc = ctx->pc & 0x1cffffff;
 
+  /* if an actual boot rom wasn't loaded into memory, a valid instruction won't
+     exist at 0x0, causing an immediate trap on start */
   if (pc == 0x0) {
     return bios_boot(bios);
   }

src/guest/bios/syscalls.c

@@ -141,8 +141,8 @@ static void bios_gdrom_mainloop(struct bios *bios) {
       enum gd_secfmt fmt = SECTOR_ANY;
       enum gd_secmask mask = MASK_DATA;
 
-      LOG_SYSCALL("GDC_DMAREAD fad=0x%x n=0x%x dst=0x%x unknown=0x%x",
-                  fad, n, dst, unknown);
+      LOG_SYSCALL("GDC_DMAREAD fad=0x%x n=0x%x dst=0x%x unknown=0x%x", fad, n,
+                  dst, unknown);
 
       /* dma read functionality changes somehow when this in non-zero */
       CHECK_EQ(unknown, 0);
@@ -253,6 +253,7 @@ static void bios_gdrom_mainloop(struct bios *bios) {
 
     case GDC_STOP: {
       LOG_FATAL("GDC_STOP");
+      /* TODO same as SPI_CD_SEEK with parameter type = stop playback */
     } break;
 
     case GDC_GET_SCD: {

src/guest/gdrom/gdrom.c

@@ -324,20 +324,50 @@ static void gdrom_spi_cmd(struct gdrom *gd, int arg) {
       gdrom_spi_end(gd);
     } break;
 
-    case SPI_CD_OPEN:
-    case SPI_CD_PLAY:
-    case SPI_CD_SEEK:
+    case SPI_CD_OPEN: {
+      LOG_FATAL("SPI_CD_OPEN");
+    } break;
+
+    case SPI_CD_PLAY: {
+      LOG_WARNING("ignoring SPI_CD_PLAY");
+
+      gd->sectnum.status = DST_PAUSE;
+
+      gdrom_spi_end(gd);
+    } break;
+
+    case SPI_CD_SEEK: {
+      enum gd_seek_type param_type = (enum gd_seek_type)(data[1] & 0xf);
+
+      LOG_WARNING("ignoring SPI_CD_SEEK");
+
+      switch (param_type) {
+        case SEEK_FAD:
+        case SEEK_MSF:
+        case SEEK_PAUSE:
+          gd->sectnum.status = DST_PAUSE;
+          break;
+        case SEEK_STOP:
+          gd->sectnum.status = DST_STANDBY;
+          break;
+      }
+
+      gdrom_spi_end(gd);
+    } break;
+
     case SPI_CD_SCAN: {
+      LOG_WARNING("ignoring SPI_CD_SCAN");
+
+      gd->sectnum.status = DST_PAUSE;
+
       gdrom_spi_end(gd);
     } break;
 
     /* SPI_CHK_SECU / SPI_REQ_SECU are part of an undocumented security check
        that has yet to be fully reverse engineered. the check doesn't seem to
-       have any side effects other than setting the drive to the PAUSE state,
-       and a valid, canned response is sent when the results are requested */
+       have any side effects, a canned response is sent when the results are
+       requested */
     case SPI_CHK_SECU: {
-      gd->sectnum.status = DST_PAUSE;
-
       gdrom_spi_end(gd);
     } break;
 
@@ -783,7 +813,7 @@ void gdrom_set_disc(struct gdrom *gd, struct disc *disc) {
 
   gd->sectnum.full = 0;
   if (gd->disc) {
-    gd->sectnum.status = DST_STANDBY;
+    gd->sectnum.status = DST_PAUSE;
     gd->sectnum.format = disc_get_format(disc);
   } else {
     gd->sectnum.status = DST_NODISC;

src/guest/gdrom/gdrom_types.h

@@ -95,6 +95,13 @@ enum gd_secfmt {
   SECTOR_M2_NOXA,
 };
 
+enum gd_seek_type {
+  SEEK_FAD = 0x1,
+  SEEK_MSF = 0x2,
+  SEEK_STOP = 0x3,
+  SEEK_PAUSE = 0x4,
+};
+
 /* internal registers accessed through holly */
 union gd_error {
   uint32_t full;