Content-Type: multipart/mixed; boundary="------------NfS1SN1AwFm9LJ0s9gng5oM3"
Message-ID: <f8a97493-a5ab-565f-825a-dd0a508f2b66@enneenne.com>
Date:   Wed, 15 Feb 2023 08:46:25 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
Subject: Re: PPS functionality for Intel Timed I/O
To:     "N, Pandith" <pandith.n@intel.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Sangannavar, Mallikarjunappa" 
        <mallikarjunappa.sangannavar@intel.com>,
        "D, Lakshmi Sowjanya" <lakshmi.sowjanya.d@intel.com>,
        "T R, Thejesh Reddy" <thejesh.reddy.t.r@intel.com>,
        "Hall, Christopher S" <christopher.s.hall@intel.com>,
        "Gross, Mark" <mark.gross@intel.com>
References: <BYAPR11MB3240A86B426158623DB9983EE1D39@BYAPR11MB3240.namprd11.prod.outlook.com>
 <fa3f1765-eb59-bf69-7f7b-14621caef6ea@enneenne.com>
 <BYAPR11MB3240801F21598EEFAEA79605E1D39@BYAPR11MB3240.namprd11.prod.outlook.com>
 <1e02cc71-baee-1e75-9160-062d563af795@enneenne.com>
 <BYAPR11MB32408E2D9758BD01EC65FB49E1DA9@BYAPR11MB3240.namprd11.prod.outlook.com>
 <f2788a74-19f8-8992-5b92-427c7b2a27ab@enneenne.com>
 <BYAPR11MB3240C6789B4C04F3BDAE34D5E1A39@BYAPR11MB3240.namprd11.prod.outlook.com>
From:   Rodolfo Giometti <giometti@enneenne.com>
Content-Language: en-US
In-Reply-To: <BYAPR11MB3240C6789B4C04F3BDAE34D5E1A39@BYAPR11MB3240.namprd11.prod.outlook.com>
Precedence: bulk

This is a multi-part message in MIME format.
--------------NfS1SN1AwFm9LJ0s9gng5oM3
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 15/02/23 08:09, N, Pandith wrote:
> Hi Rodolfo,

Hello.

>> -----Original Message-----
>> From: Rodolfo Giometti <giometti@enneenne.com>
>> Sent: Monday, February 6, 2023 4:17 PM
>> To: N, Pandith <pandith.n@intel.com>
>> Cc: linux-kernel@vger.kernel.org; Sangannavar, Mallikarjunappa
>> <mallikarjunappa.sangannavar@intel.com>; D, Lakshmi Sowjanya
>> <lakshmi.sowjanya.d@intel.com>; T R, Thejesh Reddy
>> <thejesh.reddy.t.r@intel.com>; Hall, Christopher S
>> <christopher.s.hall@intel.com>
>> Subject: Re: PPS functionality for Intel Timed I/O

[snip]

>> Mmm... I'm not sure this is correct since PPS generators should generate
>> their pulses according to system clock and not according to their internal
>> clocks even if they are synced with the system clock.
>>
> Timed I/O and system time are both driven by the *same* hardware clock.
> Timed I/O is a high precision device (nanoseconds), able to output pulses.
> The driver gets the system time and schedules output
> at target_time in the future.

OK, in this case it would be OK. Please put an appropriate note within the 
generator's code and a detailed one within Documentation/driver-api/pps.rst.

Regarding Documentation/driver-api/pps.rst let me suggest you to prose a 
separate patch to rewrite the Generators section in such a way you easily can 
add your solution at the end. A possible example is attached but feel free to 
rewrite it according to your needs.

> struct timespec64 current_time;
> current_time = ktime_get_real_ts64(&current_time);
> 
> target_time = current_time + offset_time;
> cycles = translate_system_time_to_clock_cycles(target_time);
> /* Translate function is developed as part of this driver development */
> 
> /* Schedule pulse at target_time */
> write_timedio_reg(TIMEDIO_TRIGGER, cycles);
> 
> The output always triggers with ~20 ns precision.
> It's not affected by system load or no need for drivers to disable interrupts for longer durations.
> With this driver proposal, Intel Timed I/O as PPS generator will be useful in IoT and server applications.

Great! Please also add these notes to the final Documentation.

Ciao,

Rodolfo

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

--------------NfS1SN1AwFm9LJ0s9gng5oM3
Content-Type: text/x-patch; charset=UTF-8; name="pps_rst_doc_proposal.patch"
Content-Disposition: attachment; filename="pps_rst_doc_proposal.patch"
Content-Transfer-Encoding: base64
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--------------NfS1SN1AwFm9LJ0s9gng5oM3--