The DWMAC1000 supports 2 timestamping configurations to configure how frequency adjustments are made to the ptp_clock, as well as the reported timestamp values. There was a previous attempt at upstreaming support for configuring this mode by Olivier Dautricourt and Julien Beraud a few years back [1] In a nutshell, the timestamping can be either set in fine mode or in coarse mode. In fine mode, which is the default, we use the overflow of an accumulator to trigger frequency adjustments, but by doing so we lose precision on the timetamps that are produced by the timestamping unit. The main drawback is that the sub-second increment value, used to generate timestamps, can't be set to lower than (2 / ptp_clock_freq). The "fine" qualification comes from the frequent frequency adjustments we are able to do, which is perfect for a PTP follower usecase. In Coarse mode, we don't do frequency adjustments based on an accumulator overflow. We can therefore have very fine subsecond increment values, allowing for better timestamping precision. However this mode works best when the ptp clock frequency is adjusted based on an external signal, such as a PPS input produced by a GPS clock. This mode is therefore perfect for a Grand-master usecase. We therefore attempt to map these 2 modes with the newly introduced hwtimestamp qualifiers (precise and approx). Precise mode is mapped to stmmac fine mode, and is the expected default, suitable for all cases and perfect for follower mode Approx mode is mapped to coarse mode, suitable for Grand-master. Changing between these modes is done using ethtool : - Fine mode ethtool --set-hwtimestamp-cfg eth0 index 0 qualifier precise - Coarse mode ethtool --set-hwtimestamp-cfg eth0 index 0 qualifier approx [1] : https://lore.kernel.org/netdev/20200514102808.31163-1-olivier.dautricourt@orolia.com/ Signed-off-by: Maxime Chevallier --- .../net/ethernet/stmicro/stmmac/stmmac_ethtool.c | 2 ++ drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 14 ++++++++++++++ 2 files changed, 16 insertions(+) diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c index 39fa1ec92f82..0594acbc0ead 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c @@ -1192,6 +1192,8 @@ static void stmmac_get_mm_stats(struct net_device *ndev, static const struct ethtool_ops stmmac_ethtool_ops = { .supported_coalesce_params = ETHTOOL_COALESCE_USECS | ETHTOOL_COALESCE_MAX_FRAMES, + .supported_hwtstamp_qualifiers = BIT(HWTSTAMP_PROVIDER_QUALIFIER_PRECISE) | + BIT(HWTSTAMP_PROVIDER_QUALIFIER_APPROX), .get_drvinfo = stmmac_ethtool_getdrvinfo, .get_msglevel = stmmac_ethtool_getmsglevel, .set_msglevel = stmmac_ethtool_setmsglevel, diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index 3f79b61d64b9..4859aba10aa3 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -675,6 +675,14 @@ static int stmmac_hwtstamp_set(struct net_device *dev, priv->systime_flags = STMMAC_HWTS_ACTIVE; + /* This is the "coarse" mode, where we get lower frequency adjustment + * precision, but better timestamping precision. This is useful when + * acting as a grand-master, as we usually sync with a hgh-previcision + * clock through PPS input. We default to "fine" mode. + */ + if (config->qualifier == HWTSTAMP_PROVIDER_QUALIFIER_APPROX) + priv->systime_flags &= ~PTP_TCR_TSCFUPDT; + if (priv->hwts_tx_en || priv->hwts_rx_en) { priv->systime_flags |= tstamp_all | ptp_v2 | ptp_over_ethernet | ptp_over_ipv6_udp | @@ -684,6 +692,12 @@ static int stmmac_hwtstamp_set(struct net_device *dev, stmmac_config_hw_tstamping(priv, priv->ptpaddr, priv->systime_flags); + /* Switching between coarse/fine mode also requires updating the + * subsecond increment + */ + if (priv->plat->clk_ptp_rate) + stmmac_update_subsecond_increment(priv); + priv->tstamp_config = *config; return 0; -- 2.49.0