Re: [dpdk-dev] [RFC PATCH 1/3] rte_ethdev: Add API function to read dev clock

[Shahaf Shuler <shahafs@mellanox.com>]

Hi Tom,

See few nits below. 

Wednesday, November 28, 2018 11:52 AM, Tom Barbette:
> Subject: [RFC PATCH 1/3] rte_ethdev: Add API function to read dev clock
> 
> Add rte_eth_read_clock to read the current clock of a devide.

To be explicit, the **raw** clock of the device. 

> 
> The main use is to get the current clock as written by the driver in the
> timestamp field of the pkt mbuf when timestamp offloading is enabled.

I think the main use of it is to get the device clock conversion co-eff to be able to translate the mbuf raw timestamp to a local synced time value. 

> 
> This function was missing to allow users to convert that RX timestamp field to
> real time without the complexity of the rte_timesync* facility. One can
> derivate the clock frequency by calling twice read_clock and then keep a
> common time base.
> 
> Signed-off-by: Tom Barbette <barbette@kth.se>
> ---
>  doc/guides/nics/features.rst             |  1 +
>  lib/librte_ethdev/rte_ethdev.c           | 13 +++++++++++++
>  lib/librte_ethdev/rte_ethdev.h           | 23 +++++++++++++++++++++++
>  lib/librte_ethdev/rte_ethdev_core.h      |  6 ++++++
>  lib/librte_ethdev/rte_ethdev_version.map |  1 +
>  lib/librte_mbuf/rte_mbuf.h               |  2 ++
>  6 files changed, 46 insertions(+)
> 
> diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst index
> d3f904839..45484a30f 100644
> --- a/doc/guides/nics/features.rst
> +++ b/doc/guides/nics/features.rst
> @@ -602,6 +602,7 @@ Supports Timestamp.
>  * **[provides] mbuf**: ``mbuf.ol_flags:PKT_RX_TIMESTAMP``.
>  * **[provides] mbuf**: ``mbuf.timestamp``.
>  * **[provides] rte_eth_dev_info**:
> ``rx_offload_capa,rx_queue_offload_capa:
> DEV_RX_OFFLOAD_TIMESTAMP``.
> +* **[implements] eth_dev_ops**: ``read_clock``.
> 
>  .. _nic_features_macsec_offload:
> 
> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> index 5f858174b..48e8218b2 100644
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> @@ -4124,6 +4124,19 @@ rte_eth_timesync_write_time(uint16_t port_id,
> const struct timespec *timestamp)
>  								timestamp));
>  }
> 
> +int
> +rte_eth_read_clock(uint16_t port_id, uint64_t *timestamp) {
> +	struct rte_eth_dev *dev;
> +
> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> +	dev = &rte_eth_devices[port_id];
> +
> +	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->read_clock, -
> ENOTSUP);
> +	return eth_err(port_id, (*dev->dev_ops->read_clock)(dev,
> +								timestamp));
> +}
> +
>  int
>  rte_eth_dev_get_reg_info(uint16_t port_id, struct rte_dev_reg_info *info)
> { diff --git a/lib/librte_ethdev/rte_ethdev.h
> b/lib/librte_ethdev/rte_ethdev.h index 1960f3a2d..6e3a48308 100644
> --- a/lib/librte_ethdev/rte_ethdev.h
> +++ b/lib/librte_ethdev/rte_ethdev.h
> @@ -3642,6 +3642,29 @@ int rte_eth_timesync_read_time(uint16_t
> port_id, struct timespec *time);
>   */
>  int rte_eth_timesync_write_time(uint16_t port_id, const struct timespec
> *time);
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice.
> + *
> + * Read the current clock counter of an Ethernet device
> + *
> + * This returns the current raw clock value of an Ethernet device.
> + * The value returned here is from the same clock than the one
> + * filling timestamp field of RX packets. Therefore it can be used
> + * to compute a precise conversion of the device clock to the real time.

I would add in the documentation of the function the heuristics to get the conversion co-eff.

> + *
> + * @param port_id
> + *   The port identifier of the Ethernet device.
> + * @param time
> + *   Pointer to the uint64_t that holds the raw clock value.
> + *
> + * @return
> + *   - 0: Success.
> + *   - -ENODEV: The port ID is invalid.
> + *   - -ENOTSUP: The function is not supported by the Ethernet driver.
> + */
> +int __rte_experimental rte_eth_read_clock(uint16_t port_id, uint64_t
> +*time);
> +
>  /**
>   * Config l2 tunnel ether type of an Ethernet device for filtering specific
>   * tunnel packets by ether type.
> diff --git a/lib/librte_ethdev/rte_ethdev_core.h
> b/lib/librte_ethdev/rte_ethdev_core.h
> index 8f03f83f6..86806b3eb 100644
> --- a/lib/librte_ethdev/rte_ethdev_core.h
> +++ b/lib/librte_ethdev/rte_ethdev_core.h
> @@ -322,6 +322,10 @@ typedef int (*eth_timesync_write_time)(struct
> rte_eth_dev *dev,
>  				       const struct timespec *timestamp);  /**<
> @internal Function used to get time from the device clock */
> 
> +typedef int (*eth_read_clock)(struct rte_eth_dev *dev,
> +				      uint64_t *timestamp);
> +/**< @internal Function used to get the current value of the device
> +clock. */
> +
>  typedef int (*eth_get_reg_t)(struct rte_eth_dev *dev,
>  				struct rte_dev_reg_info *info);
>  /**< @internal Retrieve registers  */
> @@ -496,6 +500,8 @@ struct eth_dev_ops {
>  	eth_timesync_read_time     timesync_read_time; /** Get the device
> clock time. */
>  	eth_timesync_write_time    timesync_write_time; /** Set the device
> clock time. */
> 
> +	eth_read_clock             read_clock;
> +
>  	eth_xstats_get_by_id_t     xstats_get_by_id;
>  	/**< Get extended device statistic values by ID. */
>  	eth_xstats_get_names_by_id_t xstats_get_names_by_id; diff --git
> a/lib/librte_ethdev/rte_ethdev_version.map
> b/lib/librte_ethdev/rte_ethdev_version.map
> index 92ac3de25..12d6c3c1d 100644
> --- a/lib/librte_ethdev/rte_ethdev_version.map
> +++ b/lib/librte_ethdev/rte_ethdev_version.map
> @@ -249,6 +249,7 @@ EXPERIMENTAL {
>  	rte_eth_switch_domain_free;
>  	rte_flow_conv;
>  	rte_flow_expand_rss;
> +	rte_eth_read_clock;
>  	rte_mtr_capabilities_get;
>  	rte_mtr_create;
>  	rte_mtr_destroy;
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h index
> 3dbc6695e..4ceefa913 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -605,6 +605,8 @@ struct rte_mbuf {
> 
>  	/** Valid if PKT_RX_TIMESTAMP is set. The unit and time reference
>  	 * are not normalized but are always the same for a given port.
> +	 * Some devices allow to query rte_eth_read_clock that will return
> the
> +	 * current device timestamp.
>  	 */
>  	uint64_t timestamp;
> 

Other than that, on the RFC - Acked-by: Shahaf Shluer <shahafs@mellanox.com>.
Let's see next the full implementation. 


> --
> 2.17.1