RPi4 and support for RTC DS3231

[Barry Scott]

I have an RPi4 running Fedora 38 with kernel 6.5.6-200.fc38.aarch64.

So far I figured out that I have to add this line to the config.txt

[pi4]
dtoverlay=i2c-rtc,ds3231

But after a reboot I am not seeing any /dev/rtc* devices.
Also I'm not seeing any rtc drivers load in lsmod output.

Should this work with the Fedora kernel?
If so what do I need to do to make the RTC show up?

Barry

[Peter Robinson]

On Thu, Oct 19, 2023 at 4:22 PM Barry Scott <barry(a)barrys-emacs.org&gt; wrote:
>  I have an RPi4 running Fedora 38 with kernel 6.5.6-200.fc38.aarch64.
>
>  So far I figured out that I have to add this line to the config.txt
>
>  [pi4]
>  dtoverlay=i2c-rtc,ds3231
>
>  But after a reboot I am not seeing any /dev/rtc* devices.
>  Also I'm not seeing any rtc drivers load in lsmod output.
>
>  Should this work with the Fedora kernel?
>  If so what do I need to do to make the RTC show up? 
You'll need to follow the general section for HAT support (it's
basically any HW that needs an overlay) and reboot and it should work:
https://fedoraproject.org/w/index.php?title=Architectures/ARM/Raspberry_P...

That RTC is supported by the rtc-ds1307 driver.

Peter

[Barry Scott]

>  On 19 Oct 2023, at 17:28, Peter Robinson <pbrobinson(a)gmail.com&gt;
> wrote:
>  
>  You'll need to follow the general section for HAT support (it's
>  basically any HW that needs an overlay) and reboot and it should work:
>
> https://fedoraproject.org/w/index.php?title=Architectures/ARM/Raspberry_P...
>  
>  That RTC is supported by the rtc-ds1307 driver. 
I missed the link at the end of the config.txt  that was Fedora specific.
Maybe you could put that Fedora specific comment at the start of config.txt in a future
release?

I have followed the steps and the RTC is working.
I would like to add a section on the RTC to the docs. If that is useful how do I go about
doing that?

But I have lost the HDMI console. I can ssh into the system and it is otherwise working.

I see the boot sequence, u-boot, grub, last message on screen is the Fedoara kernel line
announcing its version. After a few seconds where I would expect to see systemd messages
instead the monitor goes into standby.

Do I need to change setting in config.txt to make the HDMI work?

Here is my config.txt:

$ cat /boot/efi/config.txt | grep -v -e '^#' -e '^$'
[pi4]
dtoverlay=upstream-pi4
arm_boost=1
dtoverlay=vc4-kms-v3d-pi4
dtoverlay=cma,cma-256
max_framebuffers=2
dtoverlay=i2c-rtc,ds3231
[cm4]
otg_mode=1
[all]
arm_64bit=1
kernel=rpi-u-boot.bin
dtoverlay=upstream
enable_uart=1
bootcode_delay=1
gpu_mem=32
start_x=1
camera_auto_detect=1
display_auto_detect=1
hdmi_ignore_cec_init=1

Barry

[Peter Robinson]

>  You'll need to follow the general section for HAT support
> (it's
>  basically any HW that needs an overlay) and reboot and it should work:
>
> https://fedoraproject.org/w/index.php?title=Architectures/ARM/Raspberry_P...
>
>  That RTC is supported by the rtc-ds1307 driver.
>
>
>  I missed the link at the end of the config.txt  that was Fedora specific.
>  Maybe you could put that Fedora specific comment at the start of config.txt in a future
> release? 
What a fantastic suggestion, I've changed it locally. It used to a be
lot higher up but with various changes it slipped down.

>  I have followed the steps and the RTC is working.
>  I would like to add a section on the RTC to the docs. If that is useful how do I go about
> doing that? 
Sure, it's a wiki so feel free to just add it, maybe make it generic
to cover all RTCs. Let me know how you get on.

>  But I have lost the HDMI console. I can ssh into the system and it is
> otherwise working.
>
>  I see the boot sequence, u-boot, grub, last message on screen is the Fedoara kernel line
>  announcing its version. After a few seconds where I would expect to see systemd messages
>  instead the monitor goes into standby.
>
>  Do I need to change setting in config.txt to make the HDMI work? 
Nothing, it's actually broken ATM, it's a F-39 blocker and I'm hoping
to get it fixed today. There's a U-Boot thread on the mailing list and
once I have a fix I'll be posting a reply on that so keep an eye out
on the list for an update.

Peter

[Barry Scott]

>  On 20 Oct 2023, at 12:01, Peter Robinson <pbrobinson(a)gmail.com&gt;
> wrote:
>  
>  Sure, it's a wiki so feel free to just add it, maybe make it generic
>  to cover all RTCs. Let me know how you get on. 
Done.

Barry

[Barry Scott]

>  On 20 Oct 2023, at 12:01, Peter Robinson <pbrobinson(a)gmail.com&gt;
> wrote:
>  
>  Nothing, it's actually broken ATM, it's a F-39 blocker and I'm hoping
>  to get it fixed today. There's a U-Boot thread on the mailing list and
>  once I have a fix I'll be posting a reply on that so keep an eye out
>  on the list for an update. 
Let me know if there is any testing I can do to help out.

I have Rpi3 and Ppi4 hardware and can make a new sdcard for testing as needed.

Barry

[Chris Adams]

Once upon a time, Barry Scott <barry(a)barrys-emacs.org&gt; said:
>  I have an RPi4 running Fedora 38 with kernel 6.5.6-200.fc38.aarch64.
>  
>  So far I figured out that I have to add this line to the config.txt
>  
>  [pi4]
>  dtoverlay=i2c-rtc,ds3231
>  
>  But after a reboot I am not seeing any /dev/rtc* devices.
>  Also I'm not seeing any rtc drivers load in lsmod output. 
Did you do this:

https://fedoraproject.org/wiki/Architectures/ARM/Raspberry_Pi/HATs#Genera...

-- 
Chris Adams <linux(a)cmadams.net&gt;