[dpdk-dev] [PATCH v2 11/17] net/mlx5: convert timestamp to completion index

[Viacheslav Ovsiienko]

The application provides timestamps in Tx mbuf as clocks,
the hardware performs scheduling on Clock Queue completion index
match. This patch introduces the timestamp-to-completion-index
inline routine.

Signed-off-by: Viacheslav Ovsiienko <viacheslavo at mellanox.com>
Acked-by: Matan Azrad <matan at mellanox.com>
---
 drivers/net/mlx5/mlx5.h      |  2 ++
 drivers/net/mlx5/mlx5_rxtx.h | 55 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/net/mlx5/mlx5_txpp.c |  5 ++++
 3 files changed, 62 insertions(+)

diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
index e599bbb..a61394c 100644
--- a/drivers/net/mlx5/mlx5.h
+++ b/drivers/net/mlx5/mlx5.h
@@ -585,6 +585,8 @@ struct mlx5_dev_txpp {
 	rte_atomic32_t err_miss_int; /* Missed service interrupt. */
 	rte_atomic32_t err_rearm_queue; /* Rearm Queue errors. */
 	rte_atomic32_t err_clock_queue; /* Clock Queue errors. */
+	rte_atomic32_t err_ts_past; /* Timestamp in the past. */
+	rte_atomic32_t err_ts_future; /* Timestamp in the distant future. */
 };
 
 /*
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index 974a847..d082cd7 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -719,4 +719,59 @@ int mlx5_dma_unmap(struct rte_pci_device *pdev, void *addr, uint64_t iova,
 	return (ts & UINT32_MAX) + (ts >> 32) * NS_PER_S;
 }
 
+/**
+ * Convert timestamp from mbuf format to linear counter
+ * of Clock Queue completions (24 bits)
+ *
+ * @param sh
+ *   Pointer to the device shared context to fetch Tx
+ *   packet pacing timestamp and parameters.
+ * @param ts
+ *   Timestamp from mbuf to convert.
+ * @return
+ *   positive or zero value - completion ID to wait
+ *   negative value - conversion error
+ */
+static __rte_always_inline int32_t
+mlx5_txpp_convert_tx_ts(struct mlx5_dev_ctx_shared *sh, uint64_t mts)
+{
+	uint64_t ts, ci;
+	uint32_t tick;
+
+	do {
+		/*
+		 * Read atomically two uint64_t fields and compare lsb bits.
+		 * It there is no match - the timestamp was updated in
+		 * the service thread, data should be re-read.
+		 */
+		rte_compiler_barrier();
+		ci = rte_atomic64_read(&sh->txpp.ts.ci_ts);
+		ts = rte_atomic64_read(&sh->txpp.ts.ts);
+		rte_compiler_barrier();
+		if (!((ts ^ ci) << (64 - MLX5_CQ_INDEX_WIDTH)))
+			break;
+	} while (true);
+	/* Perform the skew correction, positive value to send earlier. */
+	mts -= sh->txpp.skew;
+	mts -= ts;
+	if (unlikely(mts >= UINT64_MAX / 2)) {
+		/* We have negative integer, mts is in the past. */
+		rte_atomic32_inc(&sh->txpp.err_ts_past);
+		return -1;
+	}
+	tick = sh->txpp.tick;
+	MLX5_ASSERT(tick);
+	/* Convert delta to completions, round up. */
+	mts = (mts + tick - 1) / tick;
+	if (unlikely(mts >= (1 << MLX5_CQ_INDEX_WIDTH) / 2 - 1)) {
+		/* We have mts is too distant future. */
+		rte_atomic32_inc(&sh->txpp.err_ts_future);
+		return -1;
+	}
+	mts <<= 64 - MLX5_CQ_INDEX_WIDTH;
+	ci += mts;
+	ci >>= 64 - MLX5_CQ_INDEX_WIDTH;
+	return ci;
+}
+
 #endif /* RTE_PMD_MLX5_RXTX_H_ */
diff --git a/drivers/net/mlx5/mlx5_txpp.c b/drivers/net/mlx5/mlx5_txpp.c
index 17d64ff..799b20a 100644
--- a/drivers/net/mlx5/mlx5_txpp.c
+++ b/drivers/net/mlx5/mlx5_txpp.c
@@ -858,6 +858,11 @@
 	int flags;
 	int ret;
 
+	rte_atomic32_set(&sh->txpp.err_miss_int, 0);
+	rte_atomic32_set(&sh->txpp.err_rearm_queue, 0);
+	rte_atomic32_set(&sh->txpp.err_clock_queue, 0);
+	rte_atomic32_set(&sh->txpp.err_ts_past, 0);
+	rte_atomic32_set(&sh->txpp.err_ts_future, 0);
 	/* Attach interrupt handler to process Rearm Queue completions. */
 	flags = fcntl(sh->txpp.echan->fd, F_GETFL);
 	ret = fcntl(sh->txpp.echan->fd, F_SETFL, flags | O_NONBLOCK);
-- 
1.8.3.1