[PATCH net-next v2] net: stmmac: Caclucate CDC error only once
From: Kurt Kanzenbach <kurt@linutronix.de>
Date: 2021-11-22 12:03:39
Also in:
linux-arm-kernel
Subsystem:
networking drivers, stmmac ethernet driver, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Maxime Chevallier, Linus Torvalds
The clock domain crossing error (CDC) is calculated at every fetch of Tx or Rx timestamps. It includes a division. Especially on arm32 based systems it is expensive. It also requires two conditionals in the hotpath. Add a compensation value cache to struct plat_stmmacenet_data and subtract it unconditionally in the RX/TX functions which spares the conditionals. The value is initialized to 0 and if supported calculated in the PTP initialization code. Suggested-by: Thomas Gleixner <redacted> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de> --- Changes since v1: * Coding style * Changelog Previous version: * https://lore.kernel.org/netdev/20211119081010.27084-1-kurt@linutronix.de/ (local) drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 12 ++---------- drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c | 5 +++++ include/linux/stmmac.h | 1 + 3 files changed, 8 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 21111df73719..340076b5bb38 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c@@ -511,14 +511,6 @@ bool stmmac_eee_init(struct stmmac_priv *priv) return true; } -static inline u32 stmmac_cdc_adjust(struct stmmac_priv *priv) -{ - /* Correct the clk domain crossing(CDC) error */ - if (priv->plat->has_gmac4 && priv->plat->clk_ptp_rate) - return (2 * NSEC_PER_SEC) / priv->plat->clk_ptp_rate; - return 0; -} - /* stmmac_get_tx_hwtstamp - get HW TX timestamps * @priv: driver private structure * @p : descriptor pointer
@@ -550,7 +542,7 @@ static void stmmac_get_tx_hwtstamp(struct stmmac_priv *priv, } if (found) { - ns -= stmmac_cdc_adjust(priv); + ns -= priv->plat->cdc_error_adj; memset(&shhwtstamp, 0, sizeof(struct skb_shared_hwtstamps)); shhwtstamp.hwtstamp = ns_to_ktime(ns);
@@ -587,7 +579,7 @@ static void stmmac_get_rx_hwtstamp(struct stmmac_priv *priv, struct dma_desc *p, if (stmmac_get_rx_timestamp_status(priv, p, np, priv->adv_ts)) { stmmac_get_timestamp(priv, desc, priv->adv_ts, &ns); - ns -= stmmac_cdc_adjust(priv); + ns -= priv->plat->cdc_error_adj; netdev_dbg(priv->dev, "get valid RX hw timestamp %llu\n", ns); shhwtstamp = skb_hwtstamps(skb);
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
index 580cc035536b..e14c97c04317 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c@@ -309,6 +309,11 @@ void stmmac_ptp_register(struct stmmac_priv *priv) if (priv->plat->ptp_max_adj) stmmac_ptp_clock_ops.max_adj = priv->plat->ptp_max_adj; + /* Calculate the clock domain crossing (CDC) error if necessary */ + priv->plat->cdc_error_adj = 0; + if (priv->plat->has_gmac4 && priv->plat->clk_ptp_rate) + priv->plat->cdc_error_adj = (2 * NSEC_PER_SEC) / priv->plat->clk_ptp_rate; + stmmac_ptp_clock_ops.n_per_out = priv->dma_cap.pps_out_num; stmmac_ptp_clock_ops.n_ext_ts = priv->dma_cap.aux_snapshot_n;
diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
index a6f03b36fc4f..89b8e208cd7b 100644
--- a/include/linux/stmmac.h
+++ b/include/linux/stmmac.h@@ -241,6 +241,7 @@ struct plat_stmmacenet_data { unsigned int clk_ref_rate; unsigned int mult_fact_100ns; s32 ptp_max_adj; + u32 cdc_error_adj; struct reset_control *stmmac_rst; struct reset_control *stmmac_ahb_rst; struct stmmac_axi *axi;
--
2.30.2