[v4,1/3] rte_ethdev: Add API function to read dev clock
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Commit Message
Add rte_eth_read_clock to read the raw clock of a device.
The main use is to get the device clock conversion co-efficients to be
able to translate the raw clock of the timestamp field of the pkt mbuf
to a local synced time value.
This function was missing to allow users to convert the 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 | 12 ++++++
lib/librte_ethdev/rte_ethdev.h | 47 ++++++++++++++++++++++++
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, 69 insertions(+)
Comments
On 5/2/19 3:11 PM, Tom Barbette wrote:
> Add rte_eth_read_clock to read the raw clock of a device.
>
> The main use is to get the device clock conversion co-efficients to be
> able to translate the raw clock of the timestamp field of the pkt mbuf
> to a local synced time value.
>
> This function was missing to allow users to convert the 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>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
On 5/2/2019 1:11 PM, Tom Barbette wrote:
> Add rte_eth_read_clock to read the raw clock of a device.
>
> The main use is to get the device clock conversion co-efficients to be
> able to translate the raw clock of the timestamp field of the pkt mbuf
> to a local synced time value.
>
> This function was missing to allow users to convert the 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>
<...>
> +/**
> + * @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. It is
> + * a raw amount of ticks, with no given time reference.
> + * The value returned here is from the same clock than the one
> + * filling timestamp field of Rx packets when using hardware timestamp
> + * offload. Therefore it can be used to compute a precise conversion of
> + * the device clock to the real time.
> + *
> + * E.g, a simple heuristic to derivate the frequency would be:
> + * uint64_t start, end;
> + * rte_eth_read_clock(port, start);
> + * rte_delay_ms(100);
> + * rte_eth_read_clock(port, end);
> + * double freq = (end - start) * 10;
> + *
> + * Compute a common reference with:
> + * uint64_t base_time_sec = current_time();
> + * uint64_t base_clock;
> + * rte_eth_read_clock(port, base_clock);
> + *
> + * Then, convert the raw mbuf timestamp with:
> + * base_time_sec + (double)(mbuf->timestamp - base_clock) / freq;
> + *
> + * This simple example will not provide a very good accuracy. One must
> + * at least measure multiple times the frequency and do a regression.
> + * To avoid deviation from the system time, the common reference can
> + * be repeated from time to time. The integer division can also be
> + * converted by a multiplication and a shift for better performance.
> + *
> + * @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 *clock);
This is causing doc build error, since @param should be "clock" instead of "time".
I have fixed this in the next-net repo and force pushed.
@@ -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``.
+* **[related] eth_dev_ops**: ``read_clock``.
.. _nic_features_macsec_offload:
@@ -4170,6 +4170,18 @@ 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 *clock)
+{
+ 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, clock));
+}
+
int
rte_eth_dev_get_reg_info(uint16_t port_id, struct rte_dev_reg_info *info)
{
@@ -3793,6 +3793,53 @@ 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. It is
+ * a raw amount of ticks, with no given time reference.
+ * The value returned here is from the same clock than the one
+ * filling timestamp field of Rx packets when using hardware timestamp
+ * offload. Therefore it can be used to compute a precise conversion of
+ * the device clock to the real time.
+ *
+ * E.g, a simple heuristic to derivate the frequency would be:
+ * uint64_t start, end;
+ * rte_eth_read_clock(port, start);
+ * rte_delay_ms(100);
+ * rte_eth_read_clock(port, end);
+ * double freq = (end - start) * 10;
+ *
+ * Compute a common reference with:
+ * uint64_t base_time_sec = current_time();
+ * uint64_t base_clock;
+ * rte_eth_read_clock(port, base_clock);
+ *
+ * Then, convert the raw mbuf timestamp with:
+ * base_time_sec + (double)(mbuf->timestamp - base_clock) / freq;
+ *
+ * This simple example will not provide a very good accuracy. One must
+ * at least measure multiple times the frequency and do a regression.
+ * To avoid deviation from the system time, the common reference can
+ * be repeated from time to time. The integer division can also be
+ * converted by a multiplication and a shift for better performance.
+ *
+ * @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 *clock);
+
/**
* Config l2 tunnel ether type of an Ethernet device for filtering specific
* tunnel packets by ether type.
@@ -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;
@@ -253,6 +253,7 @@ EXPERIMENTAL {
rte_eth_dev_rx_intr_ctl_q_get_fd;
rte_eth_find_next_of;
rte_eth_find_next_sibling;
+ rte_eth_read_clock;
rte_eth_switch_domain_alloc;
rte_eth_switch_domain_free;
rte_flow_conv;
@@ -668,6 +668,8 @@ 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;