[dpdk-dev] [RFC 1/4] ethdev: claim device reset as async

[Qi Zhang <qi.z.zhang@intel.com>]

rte_eth_dev_reset should be implemented in an async way since it is
possible be invoked in interrupt thread and sometimes to reset a
device need to wait for some dependency, for example, a VF expects
for PF ready, or a NIC function as part of a SOC wait for the whole
system reset complete, all these time consuming task will block the
the interrupt thread.
The patch claims rte_eth_dev_reset is an async function and introduce
a new event RTE_ETH_EVENT_RESET_COMPLETE. PMD should raise this event
when finish reset in background. The applicaiton should always wait
for this event before continue to configure and restart the device.

Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
---
 lib/librte_ethdev/rte_ethdev.h | 48 ++++++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 18 deletions(-)

diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index 7070e9ab4..541b5161d 100644
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -1814,21 +1814,34 @@ void rte_eth_dev_close(uint16_t port_id);
  * RTE_ETH_EVENT_INTR_RESET event is detected, but can also use it to start
  * a port reset in other circumstances.
  *
- * When this function is called, it first stops the port and then calls the
- * PMD specific dev_uninit( ) and dev_init( ) to return the port to initial
- * state, in which no Tx and Rx queues are setup, as if the port has been
- * reset and not started. The port keeps the port id it had before the
- * function call.
- *
- * After calling rte_eth_dev_reset( ), the application should use
- * rte_eth_dev_configure( ), rte_eth_rx_queue_setup( ),
- * rte_eth_tx_queue_setup( ), and rte_eth_dev_start( )
- * to reconfigure the device as appropriate.
- *
- * Note: To avoid unexpected behavior, the application should stop calling
- * Tx and Rx functions before calling rte_eth_dev_reset( ). For thread
- * safety, all these controlling functions should be called from the same
- * thread.
+ * @note
+ * Device reset may have the dependency, for example, a VF reset expects
+ * PF ready, or a NIC function as a part of a SOC need to wait for other
+ * parts of the system be ready, these are time-consuming tasks and will
+ * block current thread.
+ *
+ * So we claimed rte_eth_dev_reset as an async API, that makes things easy
+ * for an application that what to reset the device from the interrupt
+ * thread since typically a RTE_ETH_EVENT_INTR_RESET handler is invoked in
+ * interrupt thread.
+ *
+ * PMD is responsrible to implement ops->dev_reset in an async way, it can
+ * offload the whole task into a separate thread, or maybe just pending on
+ * hardware interrupt as reset dependency ready or start a timely alarm
+ * to poll register status as a background daemon. PMD is also responsible
+ * to raise the RTE_ETH_EVENT_RESET_COMPLETE event to notify the application
+ * when reset is complete.
+ *
+ * Application should not assume device reset is finished after
+ * rte_eth_dev_reset return, it should always wait for a
+ * RTE_ETH_EVENT_RESET_COMPLETE event and check the reset result.
+ * If reset success, application should call rte_eth_dev_configure( ),
+ * rte_eth_rx_queue_setup( ), rte_eth_tx_queue_setup( ),
+ * and rte_eth_dev_start( ) to reconfigure the device as appropriate.
+ *
+ * @Note
+ * To avoid unexpected behavior, the application should stop calling
+ * Tx and Rx functions before calling rte_eth_dev_reset( ).
  *
  * @param port_id
  *   The port identifier of the Ethernet device.
@@ -1838,9 +1851,6 @@ void rte_eth_dev_close(uint16_t port_id);
  *   - (-EINVAL) if port identifier is invalid.
  *   - (-ENOTSUP) if hardware doesn't support this function.
  *   - (-EPERM) if not ran from the primary process.
- *   - (-EIO) if re-initialisation failed or device is removed.
- *   - (-ENOMEM) if the reset failed due to OOM.
- *   - (-EAGAIN) if the reset temporarily failed and should be retried later.
  */
 int rte_eth_dev_reset(uint16_t port_id);
 
@@ -2574,6 +2584,8 @@ enum rte_eth_event_type {
 				/**< queue state event (enabled/disabled) */
 	RTE_ETH_EVENT_INTR_RESET,
 			/**< reset interrupt event, sent to VF on PF reset */
+	RTE_ETH_EVENT_RESET_COMPLETE,
+			/**< inform application that reset is completed */
 	RTE_ETH_EVENT_VF_MBOX,  /**< message from the VF received by PF */
 	RTE_ETH_EVENT_MACSEC,   /**< MACsec offload related event */
 	RTE_ETH_EVENT_INTR_RMV, /**< device removal event */
-- 
2.13.6