Subject: Re: Time: new clocksource
To:     Muni Sekhar <munisekharrms@gmail.com>, tglx@linutronix.de,
        LKML <linux-kernel@vger.kernel.org>,
        kernelnewbies <kernelnewbies@kernelnewbies.org>
References: <CAHhAz+jpmksehY4BSH9jJPYuY+jykSHtx9TNiG-gAkq10zaXSQ@mail.gmail.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <fe9dbf81-e060-36ab-b769-215af3d65ba7@linaro.org>
Date:   Fri, 3 Dec 2021 22:48:08 +0100
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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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