On Sat, Dec 4, 2021 at 3:18 AM Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
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
/var/log/kern.log file use a absolute time, like "Nov 29 12:26:13", as well as relative time in seconds and microseconds since startup , like "[1263900.984287] Is the relative time calculated by the clocksource driver module (tsc or acpi_pm)? Which module is responsible for resulting in the absolute time? Is absolute time synchronized across multiple systems connected on the network?
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-- Thanks, Sekhar