From: Martin Jerabek <jerabma7@fel.cvut.cz>
Date: Mon, 30 May 2016 16:45:48 +0000 (+0200)
Subject: latester: support for determining time offset between can interfaces (on CAN-BENCH... 
X-Git-Url: http://rtime.felk.cvut.cz/gitweb/can-benchmark.git/commitdiff_plain/95e2144f1cc7525bcae7f202b06f0825ee7d508d

latester: support for determining time offset between can interfaces (on CAN-BENCH platform)
---

diff --git a/latester/latester.c b/latester/latester.c
index a6f1453..b396fd2 100644
--- a/latester/latester.c
+++ b/latester/latester.c
@@ -94,6 +94,7 @@ int num_interfaces = 0;
 int count = 0;			/* Number of sent messages */
 unsigned msg_in_progress = 0;
 int completion_pipe[2];
+struct timespec can_tsdiff = {0, 0}; /* can_rx2_ts - can_rx1_ts */
 
 struct msg_info {
 	canid_t id;
@@ -557,6 +558,62 @@ void process_final_rx(int s)
 		error(1, errno, "completion_pipe write");
 }
 
+void determine_can_timing_offset(struct pollfd *pfd, int nifc)
+{
+	int uiofd;
+	volatile uint32_t *can_crossbar;
+	uint32_t oldreg;
+	struct can_frame frame;
+	struct timespec ts_rx1, ts_rx2, ts_dummy;
+	int res;
+
+	if(nifc < 2)
+		return;
+
+	uiofd = open("/dev/uio0", O_RDWR);
+	if(uiofd < 0)
+	{
+		perror("determine_can_timing_offset: /dev/uio0");
+		return;
+	}
+
+	can_crossbar = (volatile uint32_t *) mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, uiofd, 0);
+	if(can_crossbar == MAP_FAILED)
+	{
+		perror("mmap");
+		goto cleanup1;
+	}
+
+	// Bit: 20   19 18 17 16 14  13  12  11  10   9   8   7   6   5   4   3   2   1   0
+	//      STBY E3 E2 E1 E0 I3      I2      I1      I0      C3      C2      C1      C0
+	// C*: can* (outer can physical interface) connection line assignment (0-3)
+	// I*: ifc* (inner can network interface) connection line assignment (0-3)
+	// E*: can* output enable: 1 = connect to physical interface, 0 = disconnect from physical interface, conenect RX and TX together
+	// STBY: CAN Transceivers standby mode
+	oldreg = can_crossbar[0];
+	can_crossbar[0] = 0x00000000; // connect all interfaces together, disable output, disable standby
+
+	frame.can_id = 0x00;
+	frame.can_dlc = 4;
+	memcpy(frame.data, "SYNC", 4);
+	res = write(pfd[0].fd, &frame, sizeof(frame));
+	if(res != sizeof(frame))
+	{
+		perror("write");
+		goto cleanup2;
+	}
+
+	receive(pfd[1].fd, &frame, &ts_rx1, &ts_dummy);
+	receive(pfd[2].fd, &frame, &ts_rx2, &ts_dummy);
+	timespec_subtract(&can_tsdiff, &ts_rx2, &ts_rx1);
+
+cleanup2:
+	can_crossbar[0] = oldreg;
+	munmap((void*)can_crossbar, 4096);
+cleanup1:
+	close(uiofd);
+}
+
 void *measure_thread(void *arg)
 {
 	int s, i, ret;
@@ -613,6 +670,9 @@ void *measure_thread(void *arg)
 			pfd[i].events = POLLIN;
 	}
 
+	determine_can_timing_offset(pfd, num_interfaces);
+
+
 	set_sched_policy_and_prio(SCHED_FIFO, 40);
 
 #define SEND() send_and_check(pfd[0].fd)