DS GX: Hack around writing to a full FIFO that has a swap pending (fi…

…xes mgba.io/i/608)

CHANGES

@@ -12,6 +12,7 @@ Bugfixes:
  - DS GX: Fix 4-color texture coordinates
  - DS GX: Reset polygon attributes between buffer swaps
  - DS Video: Fix blend bit on windows for 3D layer (fixes mgba.io/i/611)
+ - DS GX: Hack around writing to a full FIFO that has a swap pending (fixes mgba.io/i/608)
 Misc:
  - DS: Set boot complete bit in RAM on boot (fixes mgba.io/i/576, mgba.io/i/580, mgba.io/i/586)
  - DS Memory: Ensure DS9 I/O is 8-byte aligned

src/ds/gx.c

@@ -1374,6 +1374,11 @@ static void DSGXWriteFIFO(struct DSGX* gx, struct DSGXEntry entry) {
 		mLOG(DS_GX, INFO, "FIFO full");
 		while (gx->p->cpuBlocked & DS_CPU_BLOCK_GX) {
 			// Can happen from STM
+			if (gx->swapBuffers) {
+				// XXX: Let's hope those GX entries aren't important, since STM isn't preemptable
+				mLOG(DS_GX, ERROR, "FIFO full with swap pending");
+				return;
+			}
 			mTimingDeschedule(&gx->p->ds9.timing, &gx->fifoEvent);
 			_fifoRun(&gx->p->ds9.timing, gx, 0);
 		}