linux-kernel - Re: [PATCH v5 10/11] Documentation: driver-api: pps: Add Intel Timed I/O PPS generator

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Date: Wed, 20 Mar 2024 17:18:18 +0100
From: Rodolfo Giometti <giometti@...eenne.com>
To: lakshmi.sowjanya.d@...el.com, tglx@...utronix.de, jstultz@...gle.com,
 corbet@....net, linux-kernel@...r.kernel.org
Cc: x86@...nel.org, netdev@...r.kernel.org, linux-doc@...r.kernel.org,
 intel-wired-lan@...ts.osuosl.org, andriy.shevchenko@...ux.intel.com,
 eddie.dong@...el.com, christopher.s.hall@...el.com,
 jesse.brandeburg@...el.com, davem@...emloft.net,
 alexandre.torgue@...s.st.com, joabreu@...opsys.com,
 mcoquelin.stm32@...il.com, perex@...ex.cz, linux-sound@...r.kernel.org,
 anthony.l.nguyen@...el.com, peter.hilber@...nsynergy.com,
 pandith.n@...el.com, mallikarjunappa.sangannavar@...el.com,
 subramanian.mohan@...el.com, basavaraj.goudar@...el.com,
 thejesh.reddy.t.r@...el.com
Subject: Re: [PATCH v5 10/11] Documentation: driver-api: pps: Add Intel Timed
 I/O PPS generator

On 19/03/24 14:05, lakshmi.sowjanya.d@...el.com wrote:
> From: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
> 
> Add Intel Timed I/O PPS usage instructions.
> 
> Co-developed-by: Pandith N <pandith.n@...el.com>
> Signed-off-by: Pandith N <pandith.n@...el.com>
> Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Acked-by: Rodolfo Giometti <giometti@...eenne.com>

> ---
>   Documentation/driver-api/pps.rst | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst
> index 78dded03e5d8..52a6d5faf885 100644
> --- a/Documentation/driver-api/pps.rst
> +++ b/Documentation/driver-api/pps.rst
> @@ -246,3 +246,25 @@ delay between assert and clear edge as small as possible to reduce system
>   latencies. But if it is too small slave won't be able to capture clear edge
>   transition. The default of 30us should be good enough in most situations.
>   The delay can be selected using 'delay' pps_gen_parport module parameter.
> +
> +
> +Intel Timed I/O PPS signal generator
> +------------------------------------
> +
> +Intel Timed I/O is a high precision device, present on 2019 and newer Intel
> +CPUs, that can generate PPS signals.
> +
> +Timed I/O and system time are both driven by same hardware clock. The signal
> +is generated with a precision of ~20 nanoseconds. The generated PPS signal
> +is used to synchronize an external device with system clock. For example,
> +share your clock with a device that receives PPS signal, generated by
> +Timed I/O device. There are dedicated Timed I/O pins to deliver the PPS signal
> +to an external device.
> +
> +Usage of Intel Timed I/O as PPS generator:
> +
> +Start generating PPS signal::
> +        $echo 1 > /sys/devices/platform/INTCxxxx\:00/enable
> +
> +Stop generating PPS signal::
> +        $echo 0 > /sys/devices/platform/INTCxxxx\:00/enable

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