| Message ID | 20211122111931.135135-1-kurt@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [net-next,v2] net: stmmac: Caclucate CDC error only once | expand |
On Mon, Nov 22, 2021 at 12:19 PM Kurt Kanzenbach <kurt@linutronix.de> wrote: > > 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 <tglx@linutronix.de> > Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de> > --- Nit: "Caclucate" in the subject
Hello: This patch was applied to netdev/net-next.git (master) by Jakub Kicinski <kuba@kernel.org>: On Mon, 22 Nov 2021 12:19:31 +0100 you wrote: > 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. > > [...] Here is the summary with links: - [net-next,v2] net: stmmac: Caclucate CDC error only once https://git.kernel.org/netdev/net-next/c/c6d5f1933085 You are awesome, thank you!
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;
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 <tglx@linutronix.de> 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/ 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(-)