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

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Message-ID: <87366rqw9b.fsf@kurt>
Date:   Fri, 19 Jun 2020 10:45:36 +0200
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Andrew Lunn <andrew@...n.ch>
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

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,
Kurt

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