Date: Fri, 07 Jun 2019 09:03:11 -0600 From: Ian Lepore <ian@freebsd.org> To: ticso@cicely.de, Nicola Mingotti <nmingotti@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: How to set PWM tunable name to ehrpwm.1 ? Message-ID: <42216eebac3c497b09f83f29faf68b0c74f903ce.camel@freebsd.org> In-Reply-To: <20190607112409.GO40697@cicely7.cicely.de> References: <68790975-a5a5-2138-ca89-117878d6cf2d@gmail.com> <20190606220639.GE13546@eldorado> <8126fa4ae0ca650ca12f28dd538e6e8c4e81b432.camel@freebsd.org> <2852b9da-e647-69a7-3218-88cfa500eadc@gmail.com> <20190607112409.GO40697@cicely7.cicely.de>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, 2019-06-07 at 13:24 +0200, Bernd Walter wrote:
> On Fri, Jun 07, 2019 at 02:08:32AM -0700, Nicola Mingotti wrote:
> >
> >
> > On 6/6/19 3:40 PM, Ian Lepore wrote:
> > > On Thu, 2019-06-06 at 16:06 -0600, Sergey Manucharian wrote:
> > > > Excerpts from Nicola Mingotti's message from Thu 06-Jun-19
> > > > 12:33:
> > > > > In my BeagleBone Black, FreeBSD-12 RELEASE, i created two
> > > > > overlays,
> > > > > pwm.dtso and pwm1.dtso. They enable the PWM pins p9.21, p9.22
> > > > > and
> > > > > respectively p9.14, p9.16. DTSO files are below.
> > > > >
> > > > > If I load both the DTBO at boot I see
> > > > > correctly|ehrpwm.0|and|ehrpwm.1|,
> > > > > associated to the correct pins. But, if i remove the
> > > > > overlay|pwm.dtbo|then i seen only|ehrpwm.0|in|sysctl -a|,
> > > > > which is
> > > > > not
> > > > > what i want, i would like to see the name|ehrpwm.1|.
> > > > >
> > > > > This is important because i must be 100% sure a certain pin
> > > > > corresponds
> > > > > the a certain tunable.This must be true even if i remove non
> > > > > relevant
> > > > > overlays in the future. I guess there must be some parameter
> > > > > in the
> > > > > DTSO
> > > > > which i don't know, i hope you can give me some directions
> > > > > about
> > > > > that.
> > > >
> > > > It is not related to your DTBO's. That's how everything works
> > > > (at
> > > > least
> > > > by default). You will see the same naming issue with serial
> > > > ports,
> > > > for
> > > > example. And not just in BBB.
> > > >
> > > > E.g. when I have enabled uart0 and uart2 they are named ttyu0
> > > > and
> > > > ttyu1,
> > > > if I have only uart2, it becomes ttyu0.
> > > >
> > > > It's easier if there is a device node in /dev, so you can
> > > > create a
> > > > symlink
> > > > with a fixed name (I have a script called by devd for my
> > > > multiple
> > > > serial
> > > > ports). However, that's not the case with PWM...
> > > >
> > > > Maybe there is an option to use persistent names for devices
> > > > that
> > > > somebody
> > > > can point to.
> > > >
> > >
> > > Nope, there's no magic thing you're missing that fixes
> > > this. Devices
> > > get named-and-numbered based on the order of instantiation.
> > >
> > > Since what really matters here is the sysctl names, we could
> > > change the
> > > driver to install the sysctl nodes using the fdt device node
> > > names
> > > instead of the freebsd newbus device names. Hmm, actually, since
> > > people may be relying on the current names, I guess what we'd
> > > have to
> > > do is install another set of sysctl names based on fdt name
> > > (basically
> > > a set of alias names).
> > >
> > > -- Ian
> > >
> >
> > I see, I agree changing the default naming scheme may damage who
> > is
> > relaying on it. It is not a good idea. Maybe it could be
> > implemented in
> > release 13.
> >
> > To Sergey. I used devd in the past, it works well. But i would
> > prefer
> > not to use it in this case, even if I had a /dev/xyz file
> > available. The
> > reason is that the /dev/xyz file would appear before the the devd
> > daemon
> > starts up (i guess), so the case would not stricly be covered by
> > what
> > the devd man page says devd should do.
> > $> man devd
> > => " ... Whenever a device is added to or removed from the device
> > tree ... "
> >
> > To Ian. The idea of the alias seems good. I don't know at all what
> > you
> > can manage to do at the kernel level with the tunables. I imagine
> > something like |dev.alias.am335x_ehrpwm.1| which actually refers
> > to
> > > EHRPWM1| not the second |ehrpwm| that got plugged into the system
> > > via
> >
> > overlay.
> >
> > Thank you for your answers
>
> I don't know if it would work for you, but I'm a happy user of devd
> for
> such things.
> This is devinfo -rv on a Pine64:
> ...
> uart0 pnpinfo name=serial@1c28000 compat=snps,dw-apb-uart
> ...
> I assume it is similar to what you should see on the beaglebone.
> It should be easy to identify a specific device via the name= entry.
> Messages to devd gets queued up and it shouldn't matter if the device
> is
> already attached when devd starts.
>
> This is what I use for USB uarts:
> attach 0 {
> device-name "uftdi[0-9]+";
> match "sernum" "FTYY82HD";
> match "interface" "0";
> action "rm /dev/manson_psu5; ln -s
> /dev/cua$ttyname /dev/manson_psu5";
> };
>
> Since uart(4) doen't offer a nice $ttyname, you have to convert the
> device-name into the matching cuau* entry.
>
Not quite the same thing. You're using a devd rule to manipulate
things in devfs. We're talking about sysctl nodes which are named
after the newbus device. It would be the equivelent of making the ftdi
driver install sysctl nodes that were named something other than
dev.uftdi.*.
-- Ian
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?42216eebac3c497b09f83f29faf68b0c74f903ce.camel>