linux-kernel - Re: Time: new clocksource

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Message-ID: <fe9dbf81-e060-36ab-b769-215af3d65ba7@linaro.org>
Date:   Fri, 3 Dec 2021 22:48:08 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Muni Sekhar <munisekharrms@...il.com>, tglx@...utronix.de,
        LKML <linux-kernel@...r.kernel.org>,
        kernelnewbies <kernelnewbies@...nelnewbies.org>
Subject: Re: Time: new clocksource

Hi Sekhar,

On 03/12/2021 17:50, Muni Sekhar wrote:
> Hi All,
> 
> We have a Digital PLL with 64 bit timer counter hardware and the
> counter is accessible from the CPU over the PCIe bus.
> 
> Is it possible to add this timer counter hardware as new clocksource
> driver? To do this, can someone please point me to the existing
> reference source code(or patch) for this task.

You can refer to the drivers located in drivers/clocksource

git annotate on one of the driver can give you the initial commit where
recent submissions explain the timer internals.

> Suppose if it is possible to add a new clocksource driver for this
> hardware then does any userspace get_timestamp* API would get the time
> from this new hardware?

It should if the timer is selected as the clocksource


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