i2c on RPi Zero?

Sat Jan 5 23:47:56 UTC 2019

simplified:

why would freebsd demand a different device tree than what
you get when you download it from raspberrypi.org <http://raspberrypi.org/>? all the internet
documentation describes how to manipulate the device tree. we
are at their mercy for the boot up folder as it is...

mdm

> On Jan 5, 2019, at 3:39 PM, Per Hedeland <per at hedeland.org> wrote:
> 
> On 2019-01-05 23:03, Emmanuel Vadot wrote:
>> On Sat, 5 Jan 2019 13:56:08 -0800
>> Oleksandr Tymoshenko <gonzo at bluezbox.com> wrote:
>>> Per Hedeland (per at hedeland.org) wrote:
>>>> On 2019-01-05 20:58, Oleksandr Tymoshenko wrote:
>>>>> Per Hedeland (per at hedeland.org) wrote:
>>>>>> I did a bit more testing on the Zero to see if the FreeBSD version
>>>>>> mattered:
>>>>>> 
>>>>>> FreeBSD-12.0-STABLE-arm-armv6-RPI-B-20190103-r342709.img - still no
>>>>>> luck.
>>>>>> 
>>>>>> FreeBSD-11.2-STABLE-arm-armv6-RPI-B-20190103-r342709.img - works!
>>>>>> (I.e. dmesg reports as below and /dev/iic{0,1} get created - I haven't
>>>>>> tested actual usage beyond having 'i2c -s' report "no devices found".)
>>>>>> 
>>>>>> I guess that the i2c support hasn't been removed intentionally,
>>>>>> i.e. this seems to be a regression - or is there some additional
>>>>>> config etc required to enable it with FreeBSD-12? The iic and iicbus
>>>>>> drivers appear to be built into the kernel in both 11 and 12.
>>>>>> 
>>>>>> (I haven't tested FreeBSD-12 on the Pi B, but I would guess that the
>>>>>> result will be the same as on the Zero, since it seems the hardware is
>>>>>> the same.)
>>>>> 
>>>>> There was a transition in device tree files between 11 and 12.
>>>>> bcm2708-rpi-0-w.dtb has i2c nodes but they're disabled by default.
>>>>> Try editing config.txt on FAT partition and adding following line:
>>>>> 
>>>>> dtparam=i2c
>>>>> 
>>>>> This should make boot firmware to enable device nodes in the device
>>>>> tree blob during the boot.
>>>> 
>>>> Thanks a lot! I can confirm that this makes i2c "work" on Zero with
>>>> 12-RELEASE (almost) to the extent described above for 11.2-STABLE (it
>>>> detects/creates only iic0, not iic1, but as far as I understand from
>>>> other sources, iic0 is all that is needed for "plain B" and thus also
>>>> for Zero).
>>>> 
>>>> Should I file a PR for this? I assume that the i2c nodes being
>>>> disabled is not intentional...
>>> 
>>> Yes, please do. There are also other devices, that should be enabled by
>>> default, like SPI.
>>  Why should we enabled them by default ?
>>  We have no correct way for switching a pin to gpio mode (you can do
>> that with gpioctl on some system but I consider it as a bug) so if I
>> want to use the i2c/spi/whatever pins as gpio and the default image set
>> it to another function I'm stuck.
>>  Using the rpi fundation dtb means that every settings that they set
>> for Linux will also be set for us, so every tutorial on the web where
>> people saying that you should set something in config.txt will apply to
>> FreeBSD too.
>>  The current settings aren't a bug, it's a feature (c).
> 
> OK... - so your take seems to be that FreeBSD users should google for
> the "Linux way" to (e.g.) enable i2c on RPi. I googled "enable i2c on
> raspberry pi" now, and indeed it brought up lots of Linux stuff, but
> unfortunately it mostly says to run 'raspi-config', which I can't find
> on my FreeBSD installation (and didn't actually expect to, of course).
> 
> If I explicitly add "config.txt" to the search string, I do indeed
> find some info about what to put in that file - but of course I
> wouldn't have done that if I didn't already know that this was the
> file that needed to be edited...
> 
> I'm all for using "standard" components (even when "standard" means
> "Linux"), and reducing the amount of FreeBSD-specific work that you
> and others need to put in to support FreeBSD on these "odd" systems -
> and as a long time (Free)BSD user, I actually prefer to edit a file
> over running some GUI tool without knowing what it does.
> 
> But I really think there needs to be a bit more help directed
> specifically at the FreeBSD user here (if there is and I just haven't
> found it, please enlighten me). A few words (besides "configuration
> for start.elf":-) about what config.txt is good for, and perhaps a
> pointer to e.g.
> https://www.raspberrypi.org/documentation/configuration/device-tree.md
> (found it from your hints, thanks!), on the
> https://wiki.freebsd.org/FreeBSD/arm/Raspberry%20Pi page may be
> enough.
> 
> And despite the whining above, I really do appreciate all your efforts
> to make it possible to run FreeBSD on these systems - many thanks!
> 
> --Per Hedeland
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