Re: [PATCH net-next] dpll: expose fractional frequency offset in ppt

[Jiri Pirko]

Mon, Jan 26, 2026 at 05:22:51PM +0100, ivecera@xxxxxxxxxx wrote:
>Currently, the dpll subsystem exports the fractional frequency offset
>(FFO) in parts per million (ppm). This granularity is insufficient for
>high-precision synchronization scenarios which often require parts per
>trillion (ppt) resolution.
>
>Add a new netlink attribute DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT
>to expose the FFO in ppt.
>
>Update the dpll netlink core to expect the driver-provided FFO value
>to be in ppt. To maintain backward compatibility with existing userspace
>tools, populate the legacy DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET
>attribute by dividing the new ppt value by 1,000,000.
>
>Update the zl3073x and mlx5 drivers to provide the FFO value in ppt:
>- zl3073x: adjust the fixed-point calculation to produce ppt (10^12)
>  instead of ppm (10^6).
>- mlx5: scale the existing ppm value by 1,000,000.
>
>Signed-off-by: Ivan Vecera <ivecera@xxxxxxxxxx>

Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>