netdev - Re: [RFC PATCH 0/5] PTP: add support for Intel's TGPIO controller

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Date:   Tue, 13 Aug 2019 10:50:06 +0300
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Richard Cochran <richardcochran@...il.com>, netdev@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "Christopher S . Hall" <christopher.s.hall@...el.com>
Subject: Re: [RFC PATCH 0/5] PTP: add support for Intel's TGPIO controller


Hi,

Andrew Lunn <andrew@...n.ch> writes:
>> Andrew Lunn <andrew@...n.ch> writes:
>> > On Tue, Jul 16, 2019 at 10:20:33AM +0300, Felipe Balbi wrote:
>> >> TGPIO is a new IP which allows for time synchronization between systems
>> >> without any other means of synchronization such as PTP or NTP. The
>> >> driver is implemented as part of the PTP framework since its features
>> >> covered most of what this controller can do.
>> >
>> > Hi Felipe
>> >
>> > Given the name TGPIO, can it also be used for plain old boring GPIO?
>> 
>> not really, no. This is a misnomer, IMHO :-) We can only assert output
>> pulses at specified intervals or capture a timestamp of an external
>> signal.
>
> Hi Felipe
>
> So i guess Intel Marketing wants to call it a GPIO, but between
> engineers can we give it a better name?

If we do that we make it difficult for those reading specification and
trying to find the matching driver.

>> > Also, is this always embedded into a SoC? Or could it actually be in a
>> > discrete NIC?
>> 
>> Technically, this could be done as a discrete, but it isn't. In any
>> case, why does that matter? From a linux-point of view, we have a device
>> driver either way.
>
> I've seen a lot of i210 used with ARM SoCs. How necessary is the tsc
> patch? Is there an architecture independent alternative?

Without the TSC patch, we don't get the timestamp we need. One can argue
that $this driver could call get_tsc_ns() directly instead of providing
a wrapper for it. But that's something else entirely.

-- 
balbi