ben-blinkenlights/ubb-vga/ubb-vga.c

/*
 * ubb-vga.c - Output video on UBB with more or less VGA timing
 *
 * Written 2011 by Werner Almesberger
 * Copyright 2011 Werner Almesberger
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

/*
 * WARNING: this program does very nasty things to the Ben and it doesn't
 * like company. In particular, it resents:
 *
 * - the MMC driver - disable it with
 *   echo jz4740-mmc.0 >/sys/bus/platform/drivers/jz4740-mmc/unbind
 * - the AT86RF230/1 kernel driver - use a kernel that doesn't have it
 * - anything that accesses the screen - kill GUI, X server, etc.
 * - the screen blanker - either disable it or make sure the screen stays
 *   dark, e.g., with
 *   echo 1 >/sys/devices/platform/jz4740-fb/graphics/fb0/blank
 * - probably a fair number of other daemons and things as well - best to
 *   kill them all.
 */


#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>


static uint8_t thres = 63;


/* ----- I/O pin assignment ------------------------------------------------ */


#define	DAT0		(1 << 10)
#define	DAT1		(1 << 11)
#define	DAT2		(1 << 12)
#define	DAT3		(1 << 13)
#define	CMD		(1 << 8)
#define	CLK		(1 << 9)

#define	R		DAT3
#define	G		DAT0
#define	B		DAT1
#define	HSYNC		CMD
#define	VSYNC		CLK


/* ----- Ben hardware ------------------------------------------------------ */


#define	TIMER		7


#define	PAGE_SIZE	4096
#define	SOC_BASE	0x10000000


static volatile uint32_t *icmr, *icmsr, *icmcr;
static uint32_t old_icmr;

static volatile uint32_t *clkgr;
static uint32_t old_clkgr;

static volatile uint32_t *pdpin, *pddats, *pddatc;
static volatile uint32_t *pddirs, *pddirc;
static volatile uint32_t *pdfuns, *pdfunc;

static volatile uint32_t *tssr, *tscr;
static volatile uint32_t *tesr, *tecr;
static volatile uint32_t *tcsr, *tdfr, *tcnt;


static void disable_interrupts(void)
{
	/*
	 * @@@ Race condition alert ! If we get interrupted/preempted between
	 * reading ICMR and masking all interrupts, and the code that runs
	 * between these two operations changes ICMR, then we may set an
	 * incorrect mask when restoring interrupts, which may hang the system.
	 */

	old_icmr = *icmr;
	*icmsr = 0xffffffff;
}


static void enable_interrupts(void)
{
	*icmcr = ~old_icmr;
}


/*
 * @@@ Disabling the LCD clock will hang operations that depend on the LCD
 * subsystem to advance. This includes the screen saver.
 */

static void disable_lcd(void)
{
	old_clkgr = *clkgr;
	*clkgr = old_clkgr | 1 << 10;
}


static void enable_lcd(void)
{
	*clkgr = old_clkgr;
}


static void get_timer(void)
{
	*tscr = 1 << TIMER;	/* enable clock */
	*tcsr = 1;		/* count at PCLK/1 */
	*tdfr = 0xffff;		/* count to 0xffff */
	*tesr = 1 << TIMER;
}


static void release_timer(void)
{
	*tecr = 1 << TIMER;
	*tssr = 1 << TIMER;
}


static void *map(off_t addr, size_t size)
{
	int fd;
	void *mem;

	fd = open("/dev/mem", O_RDWR | O_SYNC);
	if (fd < 0) {
		perror("/dev/mem");
		exit(1);
	}
	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, addr);
	if (mem == MAP_FAILED) {
		perror("mmap");
		exit(1);
	}

	return mem;
}


static void ben_setup(void)
{
	volatile void *base;

	base = map(SOC_BASE, PAGE_SIZE*3*16);

	icmr = base+0x1004;
	icmsr = base+0x1008;
	icmcr = base+0x100c;

	clkgr = base+0x20;

	pdpin = base+0x10300;
	pddats = base+0x10314;
	pddatc = base+0x10318;

	pdfuns = base+0x10344;
	pdfunc = base+0x10348;

	pddirs = base+0x10364;
	pddirc = base+0x10368;

	tssr = base+0x202c;
	tscr = base+0x203c;

	tesr = base+0x2014;
	tecr = base+0x2018;

	tcsr = base+0x204c+0x10*TIMER;
	tdfr = base+0x2040+0x10*TIMER;
	tcnt = base+0x2048+0x10*TIMER;

	/*
	 * Ironically, switching the LCD clock on and off many times only
	 * increases the risk of a hang. Therefore, we leave stop it during
	 * all the measurements and only enable it again at the end.
	 */
	disable_lcd();
	get_timer();
}


static void cleanup(void)
{
	release_timer();
	enable_lcd();
}



/* ----- Prefetch and delay logic ------------------------------------------ */


#define	BURST		32	/* bytes */


static inline void prefetch(const uint8_t *prefetch, int words)
{
	volatile const uint8_t *p = prefetch;

	while (p != prefetch+words) {
		(void) *p;
		p += BURST;
	}
}


#define	US(us)	((uint16_t) ((us)*112))


static void until(uint16_t cycles)
{
	while ((*tcnt & 0xffff) < cycles);
}


/* ----- Frame buffer output ----------------------------------------------- */


static int line_pairs = 160;	/* set/clear pairs */
static int line_cycles = US(36); /* nominally 31.77 us, but we're too slow  */


void setup(void)
{
	mlockall(MCL_CURRENT | MCL_FUTURE);
	ben_setup();
	*pdfunc = R | G | B | HSYNC | VSYNC;
	*pddirs = R | G | B | HSYNC | VSYNC;
}


static void line(const uint8_t *line, const uint8_t *fetch)
{
	const uint8_t *p = line;

	/* HSYNC */
	*tcnt = 0;
	*pddatc = HSYNC;
	prefetch(fetch, line_pairs);
	until(US(3.77));
	*pddats = HSYNC;

	/* Front porch */
	until(US(3.77+1.79));

	while (p != line+2*line_pairs) {
		*pddats = *p++ << 8;
		*pddatc = *p++ << 8;
	}

	/* Back porch */
	until(line_cycles);
}


static void hdelay(int cycles)
{
	while (cycles--) {
		*tcnt = 0;
		*pddatc = HSYNC;
		until(US(3.77));
		*pddats = HSYNC;
		until(line_cycles);
	}
}


static void frame(const uint8_t *f)
{
	const uint8_t *p;

	/* VSYNC */
	*pddatc = VSYNC;
	hdelay(2);
	*pddats = VSYNC;

	/* Front porch */
	*tcnt = 0;
	*pddatc = HSYNC;
	until(US(3.77));
	*pddats = HSYNC;

	prefetch(f, line_pairs);
	until(line_cycles);
	hdelay(31);

	for (p = f; p != f+240*2*line_pairs; p += 2*line_pairs) {
		line(p, p+line_pairs);
		line(p, p+2*line_pairs);
	}

	/* Back porch */
	hdelay(14);
}


/* ----- Frame buffer image generation ------------------------------------- */


static uint32_t pick(int set, int bit, uint32_t val)
{
	return set == bit ? val >> 8 : 0;
}


static uint32_t pattern(int set, int r, int g, int b)
{
	return pick(set, r, R) | pick(set, g, G) | pick(set, b, B);
}


static void tricolor(uint32_t *f)
{
	int pairs = 2*line_pairs*240;
	int i;

	for (i = 0; i != pairs/3; i++) {
		f[i & ~1] = R;
		f[i | 1] = G | B;
	}
	for (; i != pairs*2/3; i++) {
		f[i & ~1] = G;
		f[i | 1] = R | B;
	}

	for (; i != pairs; i++) {
		f[i & ~1] = B;
		f[i | 1] = R | G;
	}
}


static void grid(uint8_t *f)
{
	static uint32_t col[8] = {
		R | G | B,
		R,
		R | G,
		G,
		G | B,
		B,
		R | B,
		R | G | B,
	};
	int i, x, y;

	for (i = 0; i != 8; i++) {
		x = i*line_pairs/4+line_pairs/8;
		for (y = 0; y != 240; y++) {
			uint8_t *p = f+y*2*line_pairs+x;
			p[0] = p[1] = col[i] >> 8;
		}
	}
}


static void grab(uint8_t *f, int single)
{
	uint32_t *fb = map(0x01d00000, 4*320*240);
	int x, y;
	uint32_t pix;
	uint8_t r, g, b;

	for (y = 0; y != 240; y++)
		for (x = 0; x != 320; x++) {
			pix = *fb++;
			r = pix >> 16;
			g = pix >> 8;
			b = pix;
			if (single)
				*f++ = pattern(!(x & 1),
				    r >= thres, g >= thres, b >= thres);
			else {
				*f++ = pattern(1,
				    r >= thres, g >= thres, b >= thres);
				*f++ = pattern(0,
				    r >= thres, g >= thres, b >= thres);
			}
		}
}


/* ----- Command-line parsing and main loop -------------------------------- */


static void session(int frames, int single)
{
	uint8_t f[2*line_pairs*(240+1)];
	int i;

	memset(f, 0, sizeof(f));
	grab(f, single);
//	grid(f);

	disable_interrupts();

	for (i = 0; i != frames; i++)
		frame(f);

	enable_interrupts();
}


static void usage(const char *name)
{
	fprintf(stderr,
"usage: %s frames -d [threshold]\n\n"
"  frames     number of frames to display\n"
"  threshold  channel on/off threshold\n\n"
"  -d  double the number of set/clear pairs\n"
    , name);
	exit(1);
}


int main(int argc, char *const *argv)
{
	int frames;
	int single = 1;
	int c;

	while ((c = getopt(argc, argv, "d")) != EOF)
		switch (c) {
		case 'd':
			single = 0;
			line_pairs = 320;
			line_cycles = US(36+26);
			break;
		default:
			usage(*argv);
		}

	switch (argc-optind) {
	case 2:
		thres = atoi(argv[optind+1]);
		/* fall through */
	case 1:
		frames = atoi(argv[optind]);
		break;
	default:
		usage(*argv);
	}

	setup();
	session(frames, single);
	cleanup();

	return 0;
}