Messages in this thread | | | Date | Thu, 20 Jan 2011 12:51:29 -0800 | From | David Daney <> | Subject | RTC seems broken on 2.6.38-rc1 for RTCs lacking alarms. |
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The hwclock program on my MIPS Debian GNU/Linux 5.0 system quit working with 2.6.38-rc1.
This particular ds1307 has no interrupt connection, so the alarm feature cannot be used. Because of this the rtc_class_ops.set_alarm() function always will return -EINVAL
This problem appears to be related to commits: 042620a RTC: Remove UIE emulation 6610e08 RTC: Rework RTC code to use timerqueue for events
My system uses a ds1307 RTC which still works as evidenced by the kernel boot messages.
. . . rtc-ds1307 0-0068: setting system clock to 2011-01-20 19:58:48 UTC (1295553528) . . .
But hwclock now fails here is some nice strace output: . . . open("/dev/rtc0", O_RDONLY|O_LARGEFILE) = 3 ioctl(3, PRESTO_GETMOUNT or RTC_UIE_ON, 0) = 0 _newselect(4, [3], NULL, NULL, {5, 0}) = 0 (Timeout) write(2, "select() to /dev/rtc0 to wait for"..., 55select() to /dev/rtc0 to wait for clock tick timed out ) = 55 ioctl(3, PRESTO_SETPID or RTC_UIE_OFF, 0) = 0 close(3) = 0 exit_group(1) = ?
The hwclock program is asking to put the clock in UIE mode and then does a select() on it. Since the alarm doesn't work, the select times out.
Previously the ioctl(RTC_UIE_ON) would return EINVAL: . . . open("/dev/rtc0", O_RDONLY|O_LARGEFILE) = 3 ioctl(3, PRESTO_GETMOUNT or RTC_UIE_ON, 0) = -1 EINVAL (Invalid argument) ioctl(3, PRESTO_SETOPT or RTC_RD_TIME, {tm_sec=48, tm_min=41, tm_hour=20, tm_mday=20, tm_mon=0, tm_year=111, ...}) = 0 ioctl(3, PRESTO_SETOPT or RTC_RD_TIME, {tm_sec=48, tm_min=41, tm_hour=20, tm_mday=20, tm_mon=0, tm_year=111, ...}) = 0 . . .
The problem seems to be that rtc_update_irq_enable() no longer returns -EINVAL when it cannot set the alarm.
David Daney
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