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

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Message-ID: <BYAPR11MB32408E2D9758BD01EC65FB49E1DA9@BYAPR11MB3240.namprd11.prod.outlook.com>
Date:   Mon, 6 Feb 2023 10:16:49 +0000
From:   "N, Pandith" <pandith.n@...el.com>
To:     Rodolfo Giometti <giometti@...eenne.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

Hi Rodolfo,

> -----Original Message-----
> From: Rodolfo Giometti <giometti@...eenne.com>
> Sent: Monday, January 30, 2023 7:57 PM
> To: N, Pandith <pandith.n@...el.com>
> Cc: 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 15:11, N, Pandith wrote:
> > Here is a presentation link for Timed I/O device
> > https://lpc.events/event/16/contributions/1387/attachments/1051/2010/T
> > imed_IO_LPC.pdf
> 
> Thanks. I'll take a look at it.
> 
> > Intel Timed I/O PIN has both generator functionality and input capability.
> > Wanted to ask if it’s better to have two separate drivers, one under
> > client for input and other as generator driver for PPS output.
> > OR
> > Have a single client driver and user can choose the functionality
> > (either PPS output or as PPS source to capture pulses with timestamps).
> Within kernel sources PPS clients and PPS generators are placed into different
> directories, so I suppose is better to deploy two different pieces of code.
> 
We are planning to add a new PPS generator driver in drivers/pps/generators
i) Can this driver use pps_register_source to register Intel Timed I/O device for pulse generation ?

ii) To start/stop pulse, we are planning to add additional sysfs attribute from our main driver. 
Something like : /sys/class/ppsX/enable_pin
This is needed for users to start/stop pulse generation.

> However pay attention to the fact that a PPS generator should be referred to
> system's main clock and not to peripherals' clock.
> 
We can sync with the system time for pulse generation.
> 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

Regards,
Pandith