VMITMR_82C54: GE Fanuc Timer Driver

Warning: Linux kernel source code must be installed to build the driver module.

Code listing 1: Compiling and Installing the VMITMR_82C54 Driver

// From the vmitmr_82c54 base directory execute:
sh$ make
sh# make install

Code listing 2: Verify the Installation

// This is the driver module.  Make sure you use `uname -r`, not 'uname -r'.
sh$ ls /lib/modules/`uname -r`/extra/
vmitmr_82c54.ko
// This header file contains the ioctl calls and others macros
sh$ ls /usr/include/linux/hwtimer.h
vmirtc.h
// These are the device files used to access the timer devices
sh$ ls -l /dev/timer*
crw-rw-rw-    1 root     root     231,   1 Sep 12 01:43 /dev/timer1
crw-rw-rw-    1 root     root     231,   2 Sep 12 01:43 /dev/timer2
crw-rw-rw-    1 root     root     231,   3 Sep 12 01:43 /dev/timer3

Warning: The major device number 231 is not allocated within the official device list. This number could change or be in conflict with another device at some time in the future. The major device number used can be changed in the Makefile by modifying the definition DEVMAJOR:=231.

Code listing 3: Writing an application that uses the timers

// Here is some test code that demonstrates use of the onboard timers.
// This source code is included in the test directory.
// The file is called rtc_example.c


#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <linux/hwtimer.h>
#include <sys/ioctl.h>


/*===========================================================================
 * Main routine
 */
int main()
{
        const int buffer_size = 0x100000;
        int fd1, fd3, ii, start_count, end_count;
        char src[buffer_size], dest[buffer_size];
        fd_set fds;

        if (-1 == (fd1 = open("/dev/timer1", O_RDWR))) {
                perror("open");
                return -1;
        }

        if (-1 == (fd3 = open("/dev/timer2", O_RDWR))) {
                perror("open");
                return -1;
        }

        /* Set up the file descriptor we are going to poll for interrupts on.
         */
        FD_ZERO(&fds);
        FD_SET(fd1, &fds);

        start_count = 0xffff;   /* This is a 16-bit counter */
        write(fd1, &start_count, sizeof (start_count));
        ioctl(fd1, TIMER_INTERRUPT_ENABLE);
        ioctl(fd1, TIMER_START);
        write(fd3, &start_count, sizeof (start_count));

        /* Copy some data every time we get an interrupt for 5 iterations.
           Measure the time it took to complete the memcpy for each iteration.
           It is assumed that the timer is running at 1Mhz.
         */
        printf("Copying %d bytes\n", buffer_size);
        for (ii = 1; ii <= 5; ++ii) {
                /* Use select to poll for an interrupt.
                 */
                select(fd1 + 1, NULL, NULL, &fds, NULL);

                /* Write an initial count and start the timer.
                 */
                write(fd3, &start_count, sizeof (start_count));
                ioctl(fd3, TIMER_START);

                /* Do some work.
                 */
                memcpy(dest, src, buffer_size);

                /* Read back the count and determine how long it took to do
                   the work.
                 */
                ioctl(fd3, TIMER_STOP);
                read(fd3, &end_count, sizeof (end_count));
                printf("Copy %d took %dus\n", ii, start_count - end_count);
        }

        ioctl(fd1, TIMER_INTERRUPT_DISABLE);
        ioctl(fd1, TIMER_STOP);

        close(fd1);
        close(fd3);

        return 0;
}


// If you have not already done so, load the driver.
sh# modprobe vmitmr_82c54
// Now let's run our code.
sh$ ./tmr_example
Copying 1048576 bytes
Copy 1 took 11981us
Copy 2 took 9925us
Copy 3 took 9976us
Copy 4 took 9948us
Copy 5 took 9975us

Warning: The current timer count is not updated unless the timer is running, so if you just wrote a count to the device while the timer was halted, do not expect to read back the same value.