Options for FBSD support with LCD device - new project

[Daniel Braniss]

> On 18 Mar 2019, at 21:13, Ian Lepore <ian at freebsd.org> wrote:
> 
> On Mon, 2019-03-18 at 13:59 -0500, Jedi Tek'Unum wrote:
>> I’ve been lurking here for some time. Long time (commercial) unix
>> expert. Not much FBSD.
>> 
>> I’m running Linux right now on NanoPi NEO (Allwinner H3) and NEO 2
>> (Allwinner H5). Not because I love Linux (I don’t) but because it
>> works out of the box including I2C. I’d really like to use FBSD on
>> them. I hope that they will reach the same maturity as BB soon.
>> 
>> Perhaps I’m wrong but my impression following this list and searching
>> around is that I2C and SPI are not “out of the box” with FBSD on
>> these platforms.
>> 
>> I’m not all that familiar with FDT. I’d like to learn how to master
>> it. If I understood it better I could probably bring anything I
>> needed to life. BUT, that is back burner to actually completing the
>> projects I’m trying to complete (where I just need I2C access from
>> user land). I really need those things to just work out of the box
>> for now - or have clear instructions on how to enable.
>> 
>> In short I can’t use FBSD yet because it doesn’t appear ready for
>> these kinds of apps on these devices. I greatly appreciate all the
>> effort that has and is going on to get there. If I had the knowledge
>> I’d love to help, but I don’t currently.
>> 
>> Perhaps I’ve just not searched and read enough to find the jewel
>> document that explains all the FDT magic in sufficient detail. By
>> that I mean *current* FDT magic (which is another confusing aspect as
>> things seem to be in flux).
>> 
>> Any advice on these matters greatly appreciated.
>> 
>> 
> 
> I'm not sure what would give you that impression about i2c and spi.  I
> belive they're well-supported on virtually every arm SOC we have any
> support for at all (except maybe amlogic/odroid and exynos, both of
> which are rapidly bitrootting from neglect).  We have command-line
> tools to read and write data to i2c and spi devices from userland, as
> well as programmatic interfaces using ioctl() for higher-performance
> needs like a rasterized spi display.
> 
> I'm the person who does most of the i2c and spi driver work for all of
> freebsd (not just arm), and it's something we use heavily in our
> products at $work, so I tend to stay on top of it.

I have several allwinner SoC, mainly from FriendlyArm, and neither i2c or SPI work.
I have a hacked i2c that mostly works, but hangs sometimes :-), mainly
timing issues of which I have no idea how to fix.
I’m willing to help here but my knowledge of the twsi tends to zero.
hint hint …

cheers,
	danny

> 
> To enable i2c or spi on any given platform, you usually do have to
> touch some FDT code along the way.  That's because almost always, the
> pins used by i2c or spi can be used for other things as well, so the
> default config (which we get by importing fdt source code from linux)
> usually isn't set up to enable those devices.
> 
> To enable them you typically have to write and compile a small dts
> overlay and set a variable in /boot/loader.conf to have that overlay
> loaded at boot time.  None of that is hard, but there is quite a bit to
> explain, more than I can do right here in this email in the middle of a
> $work day.  I guess maybe I should write a wiki page for it.
> 
> -- Ian
> 
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