netdev - Re: [RFC PATCH 7/9] net: dsa: hellcreek: Add PTP status LEDs

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Message-ID: <20200619135212.GE304147@lunn.ch>
Date:   Fri, 19 Jun 2020 15:52:12 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Kurt Kanzenbach <kurt@...utronix.de>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Richard Cochran <richardcochran@...il.com>,
        Kamil Alkhouri <kamil.alkhouri@...offenburg.de>,
        ilias.apalodimas@...aro.org
Subject: Re: [RFC PATCH 7/9] net: dsa: hellcreek: Add PTP status LEDs

On Fri, Jun 19, 2020 at 10:45:36AM +0200, Kurt Kanzenbach wrote:
> Hi Andrew,
> 
> On Thu Jun 18 2020, Andrew Lunn wrote:
> > On Thu, Jun 18, 2020 at 08:40:27AM +0200, Kurt Kanzenbach wrote:
> >> The switch has two controllable I/Os which are usually connected to LEDs. This
> >> is useful to immediately visually see the PTP status.
> >> 
> >> These provide two signals:
> >> 
> >>  * is_gm
> >> 
> >>    This LED can be activated if the current device is the grand master in that
> >>    PTP domain.
> >> 
> >>  * sync_good
> >> 
> >>    This LED can be activated if the current device is in sync with the network
> >>    time.
> >> 
> >> Expose these via the LED framework to be controlled via user space
> >> e.g. linuxptp.
> >
> > Hi Kurt
> >
> > Is the hardware driving these signals at all? Or are these just
> > suggested names in the documentation? It would not be an issue to have
> > user space to configure them to use the heartbeat trigger, etc?
> 
> These are more like GPIOs. If a 1 is set into the register then the
> hardware drives the signal to high. The names are from the
> documentation:
> 
>  * sync_good: This signal indicates that the switch is in sync
>  * is_gm:     This signal indicates that the switch is the grand master
> 
> However, these signals have to be set by user space. Most likely these
> signals are connected to LEDs.

Thanks

Since these are general purpose LEDs, you might want to look at

Documentation/devicetree/bindings/leds/common.yaml

and implement some of the common properties. The label should ideally
correspond to the text on the case, not what the datasheet says. So
getting it from DT is a good idea. Do Hirschmanns own cases use this
text on there front plate?

	    Andrew