Date: Sun, 6 Jan 2019 16:55:39 +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: <5858669f-5627-08d3-2d7b-310bf68fe545@hedeland.org> In-Reply-To: <20190106005857.baa1313ba0f70de5a2913e6d@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> <d846cf54-6550-6ab6-58fd-3324f2df6543@hedeland.org> <20190106005857.baa1313ba0f70de5a2913e6d@bidouilliste.com>
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On 2019-01-06 00:58, Emmanuel Vadot wrote:
> On Sun, 6 Jan 2019 00:39:48 +0100
> Per Hedeland <per@hedeland.org> wrote:
>
>> 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).
>
> No, my take is that FreeBSD users should be able to tweak rpi the same
> way (more of less) than the Linux users. Unfortunatly, as you pointed
> out, sometimes it's hidden via a script/binary that do it for you.
Yes - my point is that if you search the 'net (since there is no
documentation...) about these things, most of the time you find only
Linux-specific info, that isn't usable on FreeBSD. And thus that there
should at least be *some* FreeBSD documentation - mainly pointing to
the *non*-Linux-specific info that *does* actually exist, e.g. the
page that I mention below.
> But more important is that I don't want to enable i2c (or any other
> function on pins) if the board doesn't requires it. DTS/DTB is supposed
> to represent the hardware and if the hardware doesn't have i2c (or,
> again, any other stuff on some pins) there is no reason for us to
> switch by default to those functions.
Well, I'm not sure I follow what exactly "doesn't have i2c" means in
this case, but the raspberrypi.org page clearly says that "everything
off by default" is the (new) "standard", and it certainly makes sense
to me that FreeBSD should follow it - I have no problem with that, now
that I know about it.:-)
>> 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.
>
> The wiki probably need a lot of updates on how to use i2c/spi or
> whatever on rpi* (with dtb overlays examples etc ...).
Yes, more is always better:-), but the perfect is the enemy of the
good and all that - I can't see that it's an argument for doing
nothing at all...
--Per
>> 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
>
> Cheers,
>
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