linux-kernel - RE: Intel timed i/o driver in HTE

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Message-ID: <BYAPR11MB3240CE6547117D138B1A112DE1129@BYAPR11MB3240.namprd11.prod.outlook.com>
Date:   Tue, 29 Nov 2022 18:10:25 +0000
From:   "N, Pandith" <pandith.n@...el.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Dipen Patel <dipenp@...dia.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Hall, Christopher S" <christopher.s.hall@...el.com>,
        "Gross, Mark" <mark.gross@...el.com>,
        "Sangannavar, Mallikarjunappa" 
        <mallikarjunappa.sangannavar@...el.com>,
        "D, Lakshmi Sowjanya" <lakshmi.sowjanya.d@...el.com>,
        "T R, Thejesh Reddy" <thejesh.reddy.t.r@...el.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "timestamp@...ts.linux.dev" <timestamp@...ts.linux.dev>
Subject: RE: Intel timed i/o driver in HTE


> -----Original Message-----
> From: Linus Walleij <linus.walleij@...aro.org>
> Sent: Thursday, November 24, 2022 2:53 AM
> To: N, Pandith <pandith.n@...el.com>
> Cc: Dipen Patel <dipenp@...dia.com>; linux-kernel@...r.kernel.org; Hall,
> Christopher S <christopher.s.hall@...el.com>; Gross, Mark
> <mark.gross@...el.com>; Sangannavar, Mallikarjunappa
> <mallikarjunappa.sangannavar@...el.com>; D, Lakshmi Sowjanya
> <lakshmi.sowjanya.d@...el.com>; T R, Thejesh Reddy
> <thejesh.reddy.t.r@...el.com>; andriy.shevchenko@...ux.intel.com;
> timestamp@...ts.linux.dev
> Subject: Re: Intel timed i/o driver in HTE
> 
> On Wed, Nov 23, 2022 at 3:38 PM N, Pandith <pandith.n@...el.com> wrote:
> 
> > Since the current gpio framework is inadequate to periodic output modes.
> > I thought to disentangle from gpio and develop a new hte consumer.
> > Something like hte-libcdev.c
> 
> Maybe, if Dipen wants it.
> Or maybe it needs its own subsystem.
> Or maybe it should be with whatever is using these pulse trains.
> 
> Again: what is it used for? If we have no idea what it is supposed to be used
> for, we cannot place it right, even less test it.
> 
Intel  timed i/o is mainly intended for couple of functionalities.

1. Input event capture with timestamping 
2. Generate single shot or periodic pulse train

Use cases :
a. This has multiple uses like capturing trigger time and event count
b. Calculate periodicity in case of periodic signal on input pin 
c. Most importantly, precise time synchronization between devices/sub-systems 
Ex : Share precise time from a GPS receiver to the network or
       Synchronize processor clock with external signal.

> Yours,
> Linus Walleij

Regards,
Pandith