[PATCH v3 2/6] net/intel: add read clock feature in ICE

[Hore, Soumyadeep]

The similar implementation is done in igc driver. Currently we don't read time from device.
We read the system time and send it out based on the burst calculations. The mechanism is
same in kernel drivers too.

On Sun, Jun 08, 2025 at 11:32:19AM +0000, Soumyadeep Hore wrote:
> Adding eth_ice_read_clock() feature to get current time for scheduling 
> Packets based on Tx time.
> 
> Signed-off-by: Soumyadeep Hore <soumyadeep.hore at intel.com>
> ---
>  drivers/net/intel/ice/ice_ethdev.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/net/intel/ice/ice_ethdev.c 
> b/drivers/net/intel/ice/ice_ethdev.c
> index 7cc083ca32..9478ba92df 100644
> --- a/drivers/net/intel/ice/ice_ethdev.c
> +++ b/drivers/net/intel/ice/ice_ethdev.c
> @@ -187,6 +187,7 @@ static int ice_timesync_read_time(struct 
> rte_eth_dev *dev,  static int ice_timesync_write_time(struct rte_eth_dev *dev,
>  				   const struct timespec *timestamp);  static int 
> ice_timesync_disable(struct rte_eth_dev *dev);
> +static int eth_ice_read_clock(struct rte_eth_dev *dev, uint64_t 
> +*clock);
>  static int ice_fec_get_capability(struct rte_eth_dev *dev, struct rte_eth_fec_capa *speed_fec_capa,
>  			   unsigned int num);
>  static int ice_fec_get(struct rte_eth_dev *dev, uint32_t *fec_capa); 
> @@ -317,6 +318,7 @@ static const struct eth_dev_ops ice_eth_dev_ops = {
>  	.timesync_read_time           = ice_timesync_read_time,
>  	.timesync_write_time          = ice_timesync_write_time,
>  	.timesync_disable             = ice_timesync_disable,
> +	.read_clock					  = eth_ice_read_clock,
>  	.tm_ops_get                   = ice_tm_ops_get,
>  	.fec_get_capability           = ice_fec_get_capability,
>  	.fec_get                      = ice_fec_get,
> @@ -6935,6 +6937,17 @@ ice_timesync_disable(struct rte_eth_dev *dev)
>  	return 0;
>  }
>  
> +static int
> +eth_ice_read_clock(__rte_unused struct rte_eth_dev *dev, uint64_t 
> +*clock) {
> +	struct timespec system_time;
> +
> +	clock_gettime(CLOCK_REALTIME, &system_time);
> +	*clock = system_time.tv_sec * NSEC_PER_SEC + system_time.tv_nsec;
> +
> +	return 0;
> +}
> +

I see a number of problems here:

* The "read_clock" API is for reading the time from an ethernet device.
  This is not the same a reading the system time and returning that.
* This uses a potential system call to read the time. (On some linux
  implementations I think it will avoid a system call, but even so, we
  should not add what may be a system call into these fast-path APIs)

/Bruce