ubb-vga2: new option -m to select the display mode (resolution, timing)

- ubb-vga2.c (XREs, YRES, res, res_db, setup, line, hdelay, frame,
  session): replaced hard-coded display characteristics with a mode
  database
- ubb-vga2.c (usage, main): new option -m to select the display mode
- ubb-vga2.c (session): allocate frame buffer dynamically
- ubb-vga2.c (session): since we no longer prefetch, we don't need to
  allocate space beyond the end of the frame buffer
- ubb-vga2.c (line): resurrected "quick load" and extended it to fill the
  FIFO completely

ubb-vga/ubb-vga2.c

@@ -38,10 +38,6 @@
 #include "ubb-vga.h"
 
 
-#define	XRES	640
-#define	YRES	480
-
-
 #define	REG_BASE_PTR	base
 
 static volatile void *base;
@@ -190,13 +186,25 @@ static void until(uint16_t cycles)
 /* ----- Frame buffer output ----------------------------------------------- */
 
 
-static int line_words = XRES/8;
+static const struct mode {
-//static int line_cycles = US(36); /* nominally 31.77 us, but we're too slow  */
+	const char *name;
-//static int line_cycles = US(32); /* nominally 31.77 us, but we're too slow  */
+	int xres, yres;
-static int line_cycles = US(29.7); /* nominally 31.77 us, but we're too fast */
+	int line_words;		/* xres/8 */
-/*
+	int clkdiv;		/* pixel clock = 336 MHz/(clkdiv+1) */
- * Note: 29.6 is already too short. Tricky timing.
+	int line_cycles;	/* 31.77 us for official VGA */
- */
+	int hsync_end;		/* 0.79+3.77 us for official VGA */
+} mode_db[] = {
+    { "640x480",   640, 480,  640/8, 11, US(29.7), US(0.79+3.77-0.3) },
+    { "800x600",   800, 600,  800/8,  8, US(28.7), US(2.0+3.3+0.3) },
+    /* the next one may work after adjusting the timing in "frame" */
+    { "800x600",   800, 600,  800/8,  8, US(28.2), US(2.0+3.3+0.3-0.3) },
+    /* the 1024x768 below is not great but has good parameter tolerance */
+    { "1024x768", 1024, 768, 1024/8,  8, US(36.0), US(2.0+3.3) },
+    /* illustrate underruns */
+    { "1024x768ur", 1024, 768, 1024/8,  7, US(33.5), US(0.4+2.1+0.5) },
+    { NULL }
+}, *mode = mode_db;
+
 
 void setup(void)
 {
@@ -209,8 +217,7 @@ void setup(void)
 	PDDATS = VSYNC | HSYNC;
 	PDDATC = R | G | B | Y;
 
-//	*msccdr = 20;		/* set the MSC clock to 336 MHz / 21 = 16 MHz */
+	MSCCDR = mode->clkdiv;	/* set the MSC clock to 336 MHz / 12 = 28 MHz */
-	MSCCDR = 11;		/* set the MSC clock to 336 MHz / 12 = 28 MHz */
 	CLKGR &= ~(1 << 7);	/* enable MSC clock */
 	MSC_CLKRT = 0;		/* bus clock = MSC clock / 1 */
 }
@@ -236,6 +243,7 @@ static void line(const uint32_t *line)
 
 	PDDATC = HSYNC;
 	MSC_STRPCL = 2;		/* start MMC clock output */
+	MSC_RESTO = 0xffff;
 
 	MSC_CMDAT =
 	    (1 << 10) |		/* 4 bit bus */
@@ -245,7 +253,7 @@ static void line(const uint32_t *line)
 
 	MSC_STRPCL = 4;		/* START_OP */
 
-	until(US(0.79+3.77-0.3));
+	until(mode->hsync_end);
 	/*
 	 * Adjustment value tests with the XEN-1510:
 	 *
@@ -283,11 +291,14 @@ static void line(const uint32_t *line)
 	 * of the delay to shovel bits into the MSC's FIFO.
 	 */
 
-#if 0	/* quick load */
+#if 1	/* quick load */
-	MSC_TXFIFO = *p++;
+	MSC_TXFIFO = *p++; MSC_TXFIFO = *p++; MSC_TXFIFO = *p++;
-	MSC_TXFIFO = *p++;
+	MSC_TXFIFO = *p++; MSC_TXFIFO = *p++; MSC_TXFIFO = *p++;
+	MSC_TXFIFO = *p++; MSC_TXFIFO = *p++; MSC_TXFIFO = *p++;
+	MSC_TXFIFO = *p++; MSC_TXFIFO = *p++; MSC_TXFIFO = *p++;
+	MSC_TXFIFO = *p++; MSC_TXFIFO = *p++; MSC_TXFIFO = *p++;
 #endif
-	while (p != line+line_words) {
+	while (p != line+mode->line_words) {
 		uint8_t st;
 		do {
 			st = MSC_STAT;
@@ -301,7 +312,7 @@ static void line(const uint32_t *line)
 	}
 
 fail:
-	until(line_cycles);
+	until(mode->line_cycles);
 }
 
 
@@ -312,7 +323,7 @@ static void hdelay(int cycles)
 		PDDATC = HSYNC;
 		until(US(3.77));
 		PDDATS = HSYNC;
-		until(line_cycles);
+		until(mode->line_cycles);
 	}
 }
 
@@ -338,9 +349,9 @@ static void frame(const uint32_t *f)
 	PDDATC = HSYNC;
 	until(US(3.77));
 	PDDATS = HSYNC;
-	until(line_cycles-US(0.79));
+	until(mode->line_cycles-US(0.79));
 
-	for (p = f; p != f+YRES*line_words; p += line_words)
+	for (p = f; p != f+mode->yres*mode->line_words; p += mode->line_words)
 		line(p);
 
 	/* Back porch */
@@ -353,12 +364,17 @@ static void frame(const uint32_t *f)
 
 static void session(void (*gen)(void *fb, int xres, int yres), int frames)
 {
-	uint32_t f[YRES*(line_words+1)];
+	uint32_t *f;
 	int i;
 
+	f = malloc((mode->yres*mode->line_words)*4);
+	if (!f) {
+		perror("malloc");
+		exit(1);
+	}
 	memset(f, 0, sizeof(f));
 	ccube_init();
-	gen(f, XRES, YRES);
+	gen(f, mode->xres, mode->yres);
 
 	disable_interrupts();
 
@@ -372,11 +388,12 @@ static void session(void (*gen)(void *fb, int xres, int yres), int frames)
 static void usage(const char *name)
 {
 	fprintf(stderr,
-"usage: %s [-t] frames [file]\n\n"
+"usage: %s [-t] [-r resolution] frames [file]\n\n"
 "  frames  number of frames to display\n"
 "  file    PPM file\n\n"
+"  -m mode  select the display mode, default \"%s\"\n"
 "  -t       generate a test image\n"
-    , name);
+    , name, mode_db[0].name);
 	exit(1);
 }
 
@@ -387,8 +404,18 @@ int main(int argc, char *const *argv)
 	int frames;
 	int c;
 
-	while ((c = getopt(argc, argv, "t")) != EOF)
+	while ((c = getopt(argc, argv, "m:t")) != EOF)
 		switch (c) {
+		case 'm':
+			for (mode = mode_db; mode->name; mode++)
+				if (!strcmp(mode->name, optarg))
+					break;
+			if (!mode) {
+				fprintf(stderr, "no resolution \"%s\"\n",
+				    optarg);
+				exit(1);
+			}
+			break;
 		case 't':
 			gen = tstimg;
 			break;