ubb-patgen/ubb-patgen.c: new option -d to debounce the trigger

ubb-patgen/Makefile

@@ -13,7 +13,7 @@
 CC = mipsel-openwrt-linux-gcc
 CFLAGS = -g -Wall -O9 -I../libubb/include
 LDFLAGS =
-LDLIBS = -L../libubb -lubb -lm
+LDLIBS = -L../libubb -lubb -lm -lrt
 
 MAIN = ubb-patgen
 OBJS = ubb-patgen.o

ubb-patgen/README

@@ -153,5 +153,12 @@ send the pattern immediately.
 Likewise, -t 1 waits for CLK to become 1. -t cannot be used with
 the -C option.
 
-ubb-patgen usually starts the pattern about 2 us after the
+ubb-patgen usually starts the pattern about 2-10 us after the
 trigger, but this can be delayed by other system activity.
+
+The trigger signal can be debounced with the option -d, e.g.,
+
+# ubb-patgen -t 0 -d 100us 0f0
+
+This accepts the trigger only after it has been zero for at least
+100 microseconds.

ubb-patgen/ubb-patgen.c

@@ -323,8 +323,47 @@ static void wait_shifted(const struct mmcclk *clk)
 }
 
 
+static void wait_trigger(int trigger, int debounce,
+    const struct timespec *debounce_ns)
+{
+	struct timespec end, now;
+
+	/*
+	 * @@@ could also try to use POSIX per-process timers here. May be
+	 * slightly cleaner but could increase deviations.
+	 */
+	while (1) {
+		while (PIN(UBB_CLK) != trigger);
+		if (!debounce)
+			return;
+		if (clock_gettime(CLOCK_REALTIME, &end)) {
+			perror("clock_gettime");
+			exit(1);
+		}
+		end.tv_sec += debounce_ns->tv_sec;
+		end.tv_nsec += debounce_ns->tv_nsec;
+		if (end.tv_nsec > 999999999) {
+			end.tv_nsec -= 1000000000;
+			end.tv_sec++;
+		}
+		while (PIN(UBB_CLK) == trigger) {
+			if (clock_gettime(CLOCK_REALTIME, &now)) {
+				perror("clock_gettime");
+				exit(1);
+			}
+			if (now.tv_sec > end.tv_sec)
+				return;
+			if (now.tv_sec == end.tv_sec &&
+			    now.tv_nsec >= end.tv_nsec)
+				return;
+		}
+	}
+}
+
+
 static void mmc_buffer(const struct mmcclk *clk,
-    uint8_t first, unsigned long buf, int nibbles, uint32_t mask, int trigger)
+    uint8_t first, unsigned long buf, int nibbles, uint32_t mask,
+    int trigger, int debounce, const struct timespec *debounce_ns)
 {
 	/*
 	 * If under control of the MMC controller, DATx tri-state until we
@@ -370,7 +409,7 @@ static void mmc_buffer(const struct mmcclk *clk,
 	PDFUNS = mask;
 
 	if (trigger != -1)
-		while (PIN(UBB_CLK) != trigger);
+		wait_trigger(trigger, debounce, debounce_ns);
 
 	/*
 	 * Send the pattern with DMA. Note that we still have to send the first
@@ -397,7 +436,8 @@ static void mmc_buffer(const struct mmcclk *clk,
 
 
 static void send_buffer(const struct mmcclk *clk,
-    const uint8_t *buf, int nibbles, uint32_t mask, int trigger)
+    const uint8_t *buf, int nibbles, uint32_t mask,
+    int trigger, int debounce, const struct timespec *debounce_ns)
 {
 	unsigned long phys;
 
@@ -407,12 +447,14 @@ static void send_buffer(const struct mmcclk *clk,
 	}
 
 	phys = physmem_xlat((void *) buf);
-	mmc_buffer(clk, buf[0] >> 4, phys, nibbles, mask, trigger);
+	mmc_buffer(clk, buf[0] >> 4, phys, nibbles, mask,
+	    trigger, debounce, debounce_ns);
 }
 
 
 static void dma_pattern(const struct mmcclk *clk,
-    const char *pattern, uint32_t mask, int trigger)
+    const char *pattern, uint32_t mask, int trigger,
+    int debounce, const struct timespec *debounce_ns)
 {
 	const uint8_t *buf;
 	int n;
@@ -442,7 +484,7 @@ static void dma_pattern(const struct mmcclk *clk,
 	PDDATS = (buf[0] >> 4) << 10;
 	PDDIRS = mask;
 
-	send_buffer(clk, buf, n, mask, trigger);
+	send_buffer(clk, buf, n, mask, trigger, debounce, debounce_ns);
 
 	/* Final static state: the last pattern. */
 
@@ -592,10 +634,11 @@ static void usage(const char *name)
 "usage: %s\n"
 "       %s [-q] -f freq_hz|-i interval_s\n"
 "       %s [-q] [-f freq_hz|-i interval_s] -c [active_s]\n"
-"       %s [-q] [-f freq_hz|-i interval_s] [-C|-t 0|1] [-m mask] [-p]\n"
+"       %s [-q] [-f freq_hz|-i interval_s] [-C|-t 0|1 [-d debounce_s]]\n"
-"          file|pattern\n\n"
+"         [-m mask] [-p] file|pattern\n\n"
 "  -c          output bus clock on CLK without sending a pattern\n"
 "  -C          temporarily output bus clock on CLK (for debugging)\n"
+"  -d deb_s    trigger debounce time (default: no debouncing)\n"
 "  -f freq_hz  set bus clock to the specified frequency (default: 1 MHz)\n"
 "  -i inter_s  set bus clock such that one cycle equals the specified "
   "interval\n"
@@ -630,15 +673,17 @@ int main(int argc, char **argv)
 	const char *pattern = NULL;
 	int quiet = 0, force_pattern = 0;
 	struct timespec active_ns;
-	int active_rel = 0;
+	int active_rel;
 	int keep_clk = 1;
 	uint8_t mask = 0xf;
 	int trigger = -1;
+	struct timespec debounce_ns;
+	int debounce = 0, debounce_rel;
 	char *end;
 	int c;
 	unsigned long tmp;
 
-	while ((c = getopt(argc, argv, "cCf:i:m:pqt:")) != EOF)
+	while ((c = getopt(argc, argv, "cCd:f:i:m:pqt:")) != EOF)
 		switch (c) {
 		case 'f':
 			if (!frequency(optarg, &bus_hz, &bus_rel))
@@ -654,6 +699,14 @@ int main(int argc, char **argv)
 		case 'C':
 			clkout = 1;
 			break;
+		case 'd':
+			if (!duration_timespec(optarg,
+			    &debounce_ns, &debounce_rel))
+				usage(*argv);
+			if (debounce_rel < 0)
+				usage(*argv);
+			debounce = 1;
+			break;
 		case 'm':
 			tmp = strtoul(optarg, &end, 0);
 			if (*end)
@@ -744,7 +797,8 @@ int main(int argc, char **argv)
 	mmcclk_start(&clk);
 
 	if (pattern)
-		dma_pattern(&clk, pattern, mask << 10, trigger);
+		dma_pattern(&clk, pattern, mask << 10,
+		    trigger, debounce, &debounce_ns);
 
 	if (!keep_clk)
 		if (nanosleep(&active_ns, NULL))