gpu/version-detect: GPU version detection based on nocash algorithm (#5)

Makefile

@@ -18,6 +18,7 @@ IMAGES = common \
 		gpu/transparency \
 		gpu/triangle \
 		gpu/vram-to-vram-overlap \
+		gpu/version-detect \
 		gte-fuzz \
 		mdec \
 		spu/memory-transfer \

README.md

@@ -40,6 +40,7 @@ texture-overflow         | Draws textured rectangle with UV overflowing VRAM wid
 transparency             | Draws rectangles with 4 semi-transparent blending modes
 triangle                 | Draws Gouroud shaded equilateral triangle 
 vram-to-vram-overlap     | Test GP0(80) VRAM-VRAM copy behaviour in overlapping rects
+version-detect           | Uses GP1(0x10) and GP0(0xE1) to detect GPU version
 
 ### GTE
 

gpu/version-detect/Makefile

@@ -0,0 +1,3 @@
+TARGET = version-detect.elf
+
+include ../../common-test.mk

gpu/version-detect/main.cpp

@@ -0,0 +1,37 @@
+#include <common.h>
+#include <stdint.h>
+
+int main() {
+    initVideo(320, 240);
+    printf("gpu/version-detect\n");
+
+    // GPU version detection based on nocash documentation.
+    volatile uint32_t* GP0 = (volatile uint32_t*)0x1F801810;
+    volatile uint32_t* GP1 = (volatile uint32_t*)0x1F801814;
+    volatile uint32_t* GPUREAD = (volatile uint32_t*)0x1F801810;
+    volatile uint32_t* GPUSTAT = (volatile uint32_t*)0x1F801814;
+
+    *GP1 = 0x10000004;
+    *GP1 = 0x10000007;
+
+    uint32_t res1 = *GPUREAD;
+    printf("> GPUREAD = 0x%08X\n", res1);
+
+    if ((res1 & 0x00FFFFFF) == 2) {
+      printf("* GPU version 2 [New 208pin GPU (LATE-PU-8 and up)]\n");
+    } else {
+      *GP0 = (*GPUSTAT & 0x3FFF) | 0xE1001000;
+      uint32_t dummy = *GPUREAD;
+      uint32_t res2 = *GPUSTAT;
+      printf("> dummy=0x%08X, res2=0x%08X\n", dummy, res2);
+      if (res2 & 0x00001000)
+        printf("* GPU version 1 [unknown GPU type, maybe some custom arcade/prototype version ?]\n");
+      else
+        printf("* GPU version 0 [Old 160pin GPU (EARLY-PU-8)]\n");
+    }
+
+    for (;;) {
+        VSync(0);
+    }
+    return 0;
+}