Date: Sun, 6 Jan 2019 00:39:48 +0100 From: Per Hedeland <per@hedeland.org> To: Emmanuel Vadot <manu@bidouilliste.com> Cc: Oleksandr Tymoshenko <gonzo@bluezbox.com>, freebsd-arm@freebsd.org Subject: Re: i2c on RPi Zero? Message-ID: <d846cf54-6550-6ab6-58fd-3324f2df6543@hedeland.org> In-Reply-To: <20190105230306.2ad9d0ba2c2df0e8fac5f053@bidouilliste.com> References: <229e0d36-a07b-8551-9613-0bf5748352e7@hedeland.org> <dc9441e2-9858-989e-a135-3ae37de0925b@hedeland.org> <20190105195808.GA53872@bluezbox.com> <e981729d-bb71-c74e-aaa7-86c7447b1f24@hedeland.org> <20190105215608.GA55315@bluezbox.com> <20190105230306.2ad9d0ba2c2df0e8fac5f053@bidouilliste.com>
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On 2019-01-05 23:03, Emmanuel Vadot wrote:
> On Sat, 5 Jan 2019 13:56:08 -0800
> Oleksandr Tymoshenko <gonzo@bluezbox.com> wrote:
>
>> Per Hedeland (per@hedeland.org) wrote:
>>> On 2019-01-05 20:58, Oleksandr Tymoshenko wrote:
>>>> Per Hedeland (per@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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