Adding forcing 30 fps example

src/samples/gu/vsync30FPS/Makefile.sample

@@ -0,0 +1,17 @@
+TARGET = vsync30FPS
+OBJS = vsync30FPS.o ../common/callbacks.o
+
+INCDIR =
+CFLAGS = -Wall -O2
+CXXFLAGS = $(CFLAGS) -fno-exceptions -fno-rtti
+ASFLAGS = $(CFLAGS)
+
+LIBDIR =
+LDFLAGS =
+LIBS= -lpspgu
+
+EXTRA_TARGETS = EBOOT.PBP
+PSP_EBOOT_TITLE = VSYNC 30FPS Sample
+
+PSPSDK=$(shell psp-config --pspsdk-path)
+include $(PSPSDK)/lib/build.mak

src/samples/gu/vsync30FPS/vsync30FPS.c

@@ -0,0 +1,185 @@
+/*
+ * PSP Software Development Kit - https://github.com/pspdev
+ * -----------------------------------------------------------------------
+ * Licensed under the BSD license, see LICENSE in PSPSDK root for details.
+ *
+ * VSYNC 30FPS Sample
+ * With the sceKernelRegisterSubIntrHandler(PSP_VBLANK_INT, 0, on_vblank, NULL);,
+ * the on_vblank function is going to be executed each PSP_VBLANK_INT interruption.
+ * To force 30 FPS, we must ensure the VBLANK interruption happens exactly twice,
+ * in order to achieve this, we have used 2 semaphores, so before swapping buffers,
+ * we need to ensure that both semaphores are being signaled already, 
+ * and this is what vsync30 method does.
+ * 
+ * How there are plenty of applications whose FPS are set to 30FPS,
+ * this is just an example of how we could achieve this.
+ *
+ * Copyright (c) 2005 Jesper Svennevid
+ * Copyright (c) 2025, Francisco Javier Trujillo Mata <fjtrujy@gmail.com>
+ */
+
+#include <pspkernel.h>
+#include <pspdisplay.h>
+#include <pspdebug.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+#include <string.h>
+#include <time.h>
+
+#include <pspgu.h>
+
+#include "../common/callbacks.h"
+
+PSP_MODULE_INFO("VSYNC 30FPS Sample", 0, 1, 1);
+PSP_MAIN_THREAD_ATTR(THREAD_ATTR_USER);
+
+#define BUF_WIDTH (512)
+#define SCR_WIDTH (480)
+#define SCR_HEIGHT (272)
+
+static unsigned int __attribute__((aligned(16))) list[262144];
+static unsigned int __attribute__((aligned(16))) pixels[512 * 272];
+
+static int vsync_sema_1st_id;
+static int vsync_sema_2nd_id;
+static int vsync_sema_id = -1;
+
+struct Vertex
+{
+	unsigned short u, v;
+	unsigned short color;
+	short x, y, z;
+};
+
+static void on_vblank(int sub, void *data)
+{
+	sceKernelSignalSema(vsync_sema_id ? vsync_sema_2nd_id : vsync_sema_1st_id, 1);
+	vsync_sema_id ^= 1;
+}
+
+static void vsync30(void)
+{
+	sceKernelWaitSema(vsync_sema_1st_id, 1, NULL);
+	sceKernelWaitSema(vsync_sema_2nd_id, 1, NULL);
+}
+
+static void prepare_sema(void)
+{
+	vsync_sema_1st_id = sceKernelCreateSema("vsync_sema_1st", 0, 0, 1, NULL);
+	vsync_sema_2nd_id = sceKernelCreateSema("vsync_sema_2nd", 0, 0, 1, NULL);
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned int x, y;
+
+	setupCallbacks();
+
+	// setup
+
+	void *fbp0 = guGetStaticVramBuffer(BUF_WIDTH, SCR_HEIGHT, GU_PSM_8888);
+	void *fbp1 = guGetStaticVramBuffer(BUF_WIDTH, SCR_HEIGHT, GU_PSM_8888);
+	void *zbp = guGetStaticVramBuffer(BUF_WIDTH, SCR_HEIGHT, GU_PSM_4444);
+
+	pspDebugScreenInit();
+	sceGuInit();
+
+	sceGuStart(GU_DIRECT, list);
+	sceGuDrawBuffer(GU_PSM_8888, fbp0, BUF_WIDTH);
+	sceGuDispBuffer(SCR_WIDTH, SCR_HEIGHT, fbp1, BUF_WIDTH);
+	sceGuDepthBuffer(zbp, BUF_WIDTH);
+	sceGuOffset(2048 - (SCR_WIDTH / 2), 2048 - (SCR_HEIGHT / 2));
+	sceGuViewport(2048, 2048, SCR_WIDTH, SCR_HEIGHT);
+	sceGuDepthRange(65535, 0);
+	sceGuScissor(0, 0, SCR_WIDTH, SCR_HEIGHT);
+	sceGuEnable(GU_SCISSOR_TEST);
+	sceGuFrontFace(GU_CW);
+	sceGuClear(GU_COLOR_BUFFER_BIT | GU_DEPTH_BUFFER_BIT);
+	sceGuFinish();
+	sceGuSync(GU_SYNC_FINISH, GU_SYNC_WHAT_DONE);
+
+	prepare_sema();
+	vsync_sema_id = 0;
+	sceKernelRegisterSubIntrHandler(PSP_VBLANK_INT, 0, on_vblank, NULL);
+	sceKernelEnableSubIntr(PSP_VBLANK_INT, 0);
+
+	sceDisplayWaitVblankStart();
+	sceGuDisplay(1);
+
+	int val = 0;
+
+	// generate dummy image to blit
+
+	for (y = 0; y < 272; ++y)
+	{
+		unsigned int *row = &pixels[y * 512];
+		for (x = 0; x < 480; ++x)
+		{
+			row[x] = x * y;
+		}
+	}
+
+	sceKernelDcacheWritebackAll();
+
+	float curr_ms = 1.0f;
+	struct timeval time_slices[16];
+
+	void *framebuffer = 0;
+
+	while (running())
+	{
+		sceGuStart(GU_DIRECT, list);
+
+		// copy image from ram to vram
+
+		sceGuCopyImage(GU_PSM_8888, 0, 0, 480, 272, 512, pixels, 0, 0, 512, (void *)(0x04000000 + (u32)framebuffer));
+		sceGuTexSync();
+
+		sceGuFinish();
+		sceGuSync(GU_SYNC_FINISH, GU_SYNC_WHAT_DONE);
+
+		float curr_fps = 1.0f / curr_ms;
+
+		vsync30();
+		pspDebugScreenSetOffset((int)framebuffer);
+
+		pspDebugScreenSetXY(0, 0);
+		pspDebugScreenPrintf("%d.%03d FPS", (int)curr_fps, (int)((curr_fps - (int)curr_fps) * 1000.0f));
+
+		framebuffer = sceGuSwapBuffers();
+		// simple frame rate counter
+
+		gettimeofday(&time_slices[val & 15], 0);
+
+		val++;
+
+		if (!(val & 15))
+		{
+			struct timeval last_time = time_slices[0];
+			unsigned int i;
+
+			curr_ms = 0;
+			for (i = 1; i < 16; ++i)
+			{
+				struct timeval curr_time = time_slices[i];
+
+				if (last_time.tv_usec > curr_time.tv_usec)
+				{
+					curr_time.tv_sec++;
+					curr_time.tv_usec -= 1000000;
+				}
+
+				curr_ms += ((curr_time.tv_usec - last_time.tv_usec) + (curr_time.tv_sec - last_time.tv_sec) * 1000000) * (1.0f / 1000000.0f);
+
+				last_time = time_slices[i];
+			}
+			curr_ms /= 15.0f;
+		}
+	}
+
+	sceGuTerm();
+
+	sceKernelExitGame();
+	return 0;
+}