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

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Date:   Fri, 2 Dec 2022 03:00:29 +0000
From:   "N, Pandith" <pandith.n@...el.com>
To:     Dipen Patel <dipenp@...dia.com>,
        Linus Walleij <linus.walleij@...aro.org>
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: Dipen Patel <dipenp@...dia.com>
> Sent: Wednesday, November 30, 2022 8:54 AM
> To: Linus Walleij <linus.walleij@...aro.org>; N, Pandith
> <pandith.n@...el.com>
> Cc: 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 11/23/22 1:22 PM, Linus Walleij wrote:
> > 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.
> >
> Few things I want to know from Pandith as below:
> 1. Does timed io only meant for GPIO or other signals? if other signals, what
> type of signals?
This could be time sync signals or periodic/single pulse input for timestamp support
 
> 2. In the output mode case where for example, timed io IP outputs 1ms GPIO
> pulse, does it also timestamp it for consumers to retrieve later?
No. In output mode, either single shot or periodic pulse train is generated.
But timed i/o does keep timestamp data in input mode.

> 3. Can you share rough idea you have in mind for the hte-libcdev?
a. This layer can provide ioctl based user interactions for timestamp services (input and output mode)
b. char device creation for timestamping hardware. Something like /dev/hteX 
c.  Develop a native hte consumer, which handles user space interactions of hte subsystem
> 
> > 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.
> I think it can possibly act as time sync server as one of the use case.
> >
> > Yours,
> > Linus Walleij