Re: [PATCH net] ptp: Allow exposing cycles only for clocks with free-running counter

[Pavan Chebbi]

On Wed, Oct 29, 2025 at 2:39 PM Carolina Jubran <cjubran@xxxxxxxxxx> wrote:
>
> The PTP core falls back to gettimex64 and getcrosststamp when
> getcycles64 or getcyclesx64 are not implemented. This causes the CYCLES
> ioctls to retrieve PHC real time instead of free-running cycles.
>
> Reject PTP_SYS_OFFSET_{PRECISE,EXTENDED}_CYCLES for clocks without
> free-running counter support since the result would represent PHC real
> time and system time rather than cycles and system time.
>
> Fixes: faf23f54d366 ("ptp: Add ioctl commands to expose raw cycle counter values")
> Signed-off-by: Carolina Jubran <cjubran@xxxxxxxxxx>
> Reviewed-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
> ---
>  drivers/ptp/ptp_chardev.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
> index 8106eb617c8c..c61cf9edac48 100644
> --- a/drivers/ptp/ptp_chardev.c
> +++ b/drivers/ptp/ptp_chardev.c
> @@ -561,10 +561,14 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
>                 return ptp_mask_en_single(pccontext->private_clkdata, argptr);
>
>         case PTP_SYS_OFFSET_PRECISE_CYCLES:
> +               if (!ptp->has_cycles)
> +                       return -EOPNOTSUPP;
>                 return ptp_sys_offset_precise(ptp, argptr,
>                                               ptp->info->getcrosscycles);
>
>         case PTP_SYS_OFFSET_EXTENDED_CYCLES:
> +               if (!ptp->has_cycles)
> +                       return -EOPNOTSUPP;
>                 return ptp_sys_offset_extended(ptp, argptr,
>                                                ptp->info->getcyclesx64);
>         default:

LGTM.
Reviewed-by: Pavan Chebbi <pavan.chebbi@xxxxxxxxxxxx>

> --
> 2.38.1
>
>

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