Re: DS3231 RTC module not detected

On Sat, Feb 19, 2022 at 1:02 PM Brian Scott <bscott@bunyatech.com.au> wrote:

> On 19/2/22 9:52 am, Daniel O'Connor wrote:
> >
> >> On 19 Feb 2022, at 00:52, Archimedes Gaviola <
> archimedes.gaviola@gmail.com> wrote:
> >> Thanks for the info! I followed similar with your DS1307 RTC by
> creating a ds3231.dtso file and then compiling it with dtc to generate a
> ds3231.dtbo. The result is it is detected as MAX77620 RTC on 0xd0 address
> but when I run an i2c scan, the address detected is 68. Does this should
> match?
> > Mine was detected similarly:
> > iic0: <I2C generic I/O> on iicbus0
> > rtc0: <MAX77620 RTC> at addr 0xd0 on iicbus0
> > usbus0: 5.0Gbps Super Speed USB v3.0
> > rtc0: registered as a time-of-day clock, resolution 1.000000s
> >
> > I am not sure why it shows up like that but it does seem to work.
> >
> >> With this setup I could update the date and time now by initiating an
> ntpdate to match our time plus invoking tzsetup command for my timezone
> which is doing well without any issue. Now, the moment I shutdown the
> system and plug back the power cable (with disconnected Ethernet cable just
> to make sure NTP servers are not called for updates upon restart) the time
> remains as it was before shutting down and then upon bootup system clock
> continues. I am expecting that it should be real time even if the RPi4
> system is shutdown or detached from power due to the battery that will
> sustain the continuity of the clock. I'm sure that I'm having good DS3231
> modules as I also tested my existing and another new spare and it is tested
> with OpenBSD too. Below are the system info. Is there anything I've missed?
> FreeBSD 13.0-RELEASE have the same outcome and behavior.
> > That is strange, I tested powering mine off and it kept time but I am
> not 100% sure it was advancing correctly - I didn't take a precise note of
> when I powered it off etc..
> >
> > Unfortunately it's not physically with me so I can't test it right now.
> >
> > I do note this sysctl:
> > machdep.rtc_save_period: Save system time to RTC with this period (in
> seconds)
> >
> > Which suggests to me that the clock could be up to 30 minutes off if the
> power is removed (I believe it gets flushed out on a clean shutdown
> though). Perhaps that is the problem?
> >
> > --
> > Daniel O'Connor
> > "The nice thing about standards is that there
> > are so many of them to choose from."
> >   -- Andrew Tanenbaum
> >
> >
> Hi people,
>
> I had the same problem a few months ago.
>
> The MAX77620 driver introduced for an NVIDIA TEGRA210 system seems to
> unilaterally claim anything at address 68. It doesn't understand the
> DS3231 and fails to operate properly, but in claiming the device, the
> ds3231 driver doesn't get a chance. This is compounded by the MAX77620
> driver being compiled into the kernel by default so the loadable module
> doesn't get to try until after the wrong driver has claimed it.
>
> The only answer at present is to build a custom kernel without the
> unwanted driver. My kernel config is:
>
> include         GENERIC
> ident           GENERIC-PI
> nooptions       SOC_NVIDIA_TEGRA210
>
> Ideally, the TEGRA210 code would be fixed or removed from the GENERIC
> kernel but that doesn't seem to have happened despite the adverse effect
> on the many clock devices that live at address 68 and will already be in
> use.
>
> I dislike building a custom kernel because everything else I do strives
> to use precompiled binaries whenever possible.
>

Okay, that explains. After re-compiling the kernel my system now already
detects the module. This is with 13.0-RELEASE.

root@fbsd13:~ # kldload ds3231
ds32310: <Maxim DS3231 RTC> at addr 0xd0 on iicbus0
ds32310: registered as a time-of-day clock, resolution 1.000000s

freebsd@fbsd13:~ % sysctl -a | grep ds3231
        value:  /boot/kernel/ds3231.ko
dev.ds3231.0.32khz_enable: 1
dev.ds3231.0.sqw_mode: interrupt
dev.ds3231.0.sqw_freq: 8192
dev.ds3231.0.bbsqw: 0
dev.ds3231.0.temp_conv: 0
dev.ds3231.0.temperature: 39.1C
dev.ds3231.0.%parent: iicbus0
dev.ds3231.0.%pnpinfo: name=ds3231@68 compat=maxim,ds3231
dev.ds3231.0.%location: addr=0xd0
dev.ds3231.0.%driver: ds3231
dev.ds3231.0.%desc: Maxim DS3231 RTC
dev.ds3231.%parent:

I'm on my way with 14.0-CURRENT kernel recompilation.

Thanks a lot Brian for sharing the info and resolution! It is well
appreciated.

Thanks,
Archimedes