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

[Carolina Jubran <cjubran@nvidia.com>]

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@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
---
 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:
-- 
2.38.1