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Re: select() to /dev/rtc0 to wait for clock tick timed out

To: Matt Turner <mattst88@gmail.com>
Subject: Re: select() to /dev/rtc0 to wait for clock tick timed out
From: john stultz <johnstul@us.ibm.com>
Date: Fri, 19 Aug 2011 12:59:50 -0700
Cc: linux-mips@linux-mips.org
In-reply-to: <CAEdQ38F4zi76ug+ABZPnPLcLvGfUFRhr6SKzYCN+24Otq+qAAQ@mail.gmail.com>
References: <CAEdQ38HGfd9YWE+WLuirE4Km6UE6N26toTj=-1BuXAQUux6t5g@mail.gmail.com> <1313777242.2970.131.camel@work-vm> <CAEdQ38F4zi76ug+ABZPnPLcLvGfUFRhr6SKzYCN+24Otq+qAAQ@mail.gmail.com>
Sender: linux-mips-bounce@linux-mips.org
On Fri, 2011-08-19 at 15:41 -0400, Matt Turner wrote:
> On Fri, Aug 19, 2011 at 2:07 PM, john stultz <johnstul@us.ibm.com> wrote:
> > On Fri, 2011-08-19 at 00:16 -0400, Matt Turner wrote:
> > thanks
> > -john
> 
> Counting 5 update (1/sec) interrupts from reading /dev/rtc0:
> 
> ... and then it doesn't count.
> 
> Would it help if I tried to bisect this? (Is there an easy way to
> bisect 2.6.37..master with my patches applied to each iteration?)

I suspect bisecting won't help too much, as I've reworked a good chunk
of the generic rtc code in 2.6.38, so its not likely to be one small
change.

How about this modified (cutting out the UIE testing) version of the
Documentation/rtc.txt test below?

I'm basically trying to find out if the alarm functionality is actually
working or not, since with 2.6.38+ we use the one-shot style alarm mode
to trigger UIE interrupts.

thanks
-john



/*
 *      Real Time Clock Driver Test/Example Program
 *
 *      Compile with:
 *                   gcc -s -Wall -Wstrict-prototypes rtctest.c -o rtctest
 *
 *      Copyright (C) 1996, Paul Gortmaker.
 *
 *      Released under the GNU General Public License, version 2,
 *      included herein by reference.
 *
 */

#include <stdio.h>
#include <linux/rtc.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>


/*
 * This expects the new RTC class driver framework, working with
 * clocks that will often not be clones of what the PC-AT had.
 * Use the command line to specify another RTC if you need one.
 */
static const char default_rtc[] = "/dev/rtc0";


int main(int argc, char **argv)
{
        int i, fd, retval, irqcount = 0;
        unsigned long tmp, data;
        struct rtc_time rtc_tm;
        const char *rtc = default_rtc;

        switch (argc) {
        case 2:
                rtc = argv[1];
                /* FALLTHROUGH */
        case 1:
                break;
        default:
                fprintf(stderr, "usage:  rtctest [rtcdev]\n");
                return 1;
        }

        fd = open(rtc, O_RDONLY);

        if (fd ==  -1) {
                perror(rtc);
                exit(errno);
        }

        fprintf(stderr, "\n\t\t\tRTC Driver Test Example.\n\n");

test_READ:
        /* Read the RTC time/date */
        retval = ioctl(fd, RTC_RD_TIME, &rtc_tm);
        if (retval == -1) {
                perror("RTC_RD_TIME ioctl");
                exit(errno);
        }

        fprintf(stderr, "\n\nCurrent RTC date/time is %d-%d-%d, 
%02d:%02d:%02d.\n",
                rtc_tm.tm_mday, rtc_tm.tm_mon + 1, rtc_tm.tm_year + 1900,
                rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);

        /* Set the alarm to 5 sec in the future, and check for rollover */
        rtc_tm.tm_sec += 5;
        if (rtc_tm.tm_sec >= 60) {
                rtc_tm.tm_sec %= 60;
                rtc_tm.tm_min++;
        }
        if (rtc_tm.tm_min == 60) {
                rtc_tm.tm_min = 0;
                rtc_tm.tm_hour++;
        }
        if (rtc_tm.tm_hour == 24)
                rtc_tm.tm_hour = 0;

        retval = ioctl(fd, RTC_ALM_SET, &rtc_tm);
        if (retval == -1) {
                if (errno == ENOTTY) {
                        fprintf(stderr,
                                "\n...Alarm IRQs not supported.\n");
                        goto test_PIE;
                }
                perror("RTC_ALM_SET ioctl");
                exit(errno);
        }

        /* Read the current alarm settings */
        retval = ioctl(fd, RTC_ALM_READ, &rtc_tm);
        if (retval == -1) {
                perror("RTC_ALM_READ ioctl");
                exit(errno);
        }

        fprintf(stderr, "Alarm time now set to %02d:%02d:%02d.\n",
                rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);

        /* Enable alarm interrupts */
        retval = ioctl(fd, RTC_AIE_ON, 0);
        if (retval == -1) {
                perror("RTC_AIE_ON ioctl");
                exit(errno);
        }

        fprintf(stderr, "Waiting 5 seconds for alarm...");
        fflush(stderr);
        /* This blocks until the alarm ring causes an interrupt */
        retval = read(fd, &data, sizeof(unsigned long));
        if (retval == -1) {
                perror("read");
                exit(errno);
        }
        irqcount++;
        fprintf(stderr, " okay. Alarm rang.\n");

        /* Disable alarm interrupts */
        retval = ioctl(fd, RTC_AIE_OFF, 0);
        if (retval == -1) {
                perror("RTC_AIE_OFF ioctl");
                exit(errno);
        }

test_PIE:
        /* Read periodic IRQ rate */
        retval = ioctl(fd, RTC_IRQP_READ, &tmp);
        if (retval == -1) {
                /* not all RTCs support periodic IRQs */
                if (errno == ENOTTY) {
                        fprintf(stderr, "\nNo periodic IRQ support\n");
                        goto done;
                }
                perror("RTC_IRQP_READ ioctl");
                exit(errno);
        }
        fprintf(stderr, "\nPeriodic IRQ rate is %ldHz.\n", tmp);

        fprintf(stderr, "Counting 20 interrupts at:");
        fflush(stderr);

        /* The frequencies 128Hz, 256Hz, ... 8192Hz are only allowed for root. 
*/
        for (tmp=2; tmp<=64; tmp*=2) {

                retval = ioctl(fd, RTC_IRQP_SET, tmp);
                if (retval == -1) {
                        /* not all RTCs can change their periodic IRQ rate */
                        if (errno == ENOTTY) {
                                fprintf(stderr,
                                        "\n...Periodic IRQ rate is fixed\n");
                                goto done;
                        }
                        perror("RTC_IRQP_SET ioctl");
                        exit(errno);
                }

                fprintf(stderr, "\n%ldHz:\t", tmp);
                fflush(stderr);

                /* Enable periodic interrupts */
                retval = ioctl(fd, RTC_PIE_ON, 0);
                if (retval == -1) {
                        perror("RTC_PIE_ON ioctl");
                        exit(errno);
                }

                for (i=1; i<21; i++) {
                        /* This blocks */
                        retval = read(fd, &data, sizeof(unsigned long));
                        if (retval == -1) {
                                perror("read");
                                exit(errno);
                        }
                        fprintf(stderr, " %d",i);
                        fflush(stderr);
                        irqcount++;
                }

                /* Disable periodic interrupts */
                retval = ioctl(fd, RTC_PIE_OFF, 0);
                if (retval == -1) {
                        perror("RTC_PIE_OFF ioctl");
                        exit(errno);
                }
        }

done:
        fprintf(stderr, "\n\n\t\t\t *** Test complete ***\n");

        close(fd);

        return 0;
}



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