linux-kernel - Re: PPS functionality for Intel Timed I/O

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Date:   Mon, 30 Jan 2023 14:45:27 +0100
From:   Rodolfo Giometti <giometti@...eenne.com>
To:     "N, Pandith" <pandith.n@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Sangannavar, Mallikarjunappa" 
        <mallikarjunappa.sangannavar@...el.com>,
        "D, Lakshmi Sowjanya" <lakshmi.sowjanya.d@...el.com>,
        "T R, Thejesh Reddy" <thejesh.reddy.t.r@...el.com>,
        "Hall, Christopher S" <christopher.s.hall@...el.com>
Subject: Re: PPS functionality for Intel Timed I/O

On 30/01/23 13:55, N, Pandith wrote:
> Hi Rodolfo Giometti,

Hello.

> This is regarding Intel Timed I/O device as PPS.
> 
> Intel Timed I/O is a precise device (10s of nanoseconds), that can send out pulses.
> This is needed in IoT and server applications to measure offset between system clocks on multiple devices

Can you please provide some URLs where to get further info from about this 
device? I'd like to know how this device works and its interfaces towards the CPU.

> We are planning to implement a driver, for PPS output functionality using Timed I/O device.

Great! :)

> 	1. Is there any support from PPS framework to start/stop pulse generation.
> 	If yes, can we get the Pin number, offset(start time) from user space ?

Nope, PPS signals are supposed to be always on. However you can start/stop 
pulses generation within the main driver of your device.

> 	2. Further, this device has the capability to capture the input events (pulses, nanosecond precision).
> 	The same PIN can work in either input or output mode.
> 	Can there be an PPS client driver supporting both modes ?

I'm not sure to well understand what you mean, however a PPS client is a piece 
of code that captures PPS pulses and add a timestamp to them, while a PPS 
generator is a piece of code that (precisely) generates a PPS source according 
to the system's main clock (and not according to a peripheral's clock). Hope 
I've answered to your questions, if not feel free to ask more.

Ciao,

Rodolfo

-- 
GNU/Linux Solutions                  e-mail: giometti@...eenne.com
Linux Device Driver                          giometti@...ux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti