From: Stefan Eichenberger Add a new flag, PHY_F_KEEP_PREAMBLE_BEFORE_SFD, to indicate that the PHY shall not remove the preamble before the SFD if it supports it. MACs that do not support receiving frames without a preamble can set this flag. Signed-off-by: Stefan Eichenberger --- include/linux/phy.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/include/linux/phy.h b/include/linux/phy.h index fbbe028cc4b7b..a978173c0e2a1 100644 --- a/include/linux/phy.h +++ b/include/linux/phy.h @@ -802,8 +802,9 @@ struct phy_device { }; /* Generic phy_device::dev_flags */ -#define PHY_F_NO_IRQ 0x80000000 -#define PHY_F_RXC_ALWAYS_ON 0x40000000 +#define PHY_F_NO_IRQ 0x80000000 +#define PHY_F_RXC_ALWAYS_ON 0x40000000 +#define PHY_F_KEEP_PREAMBLE_BEFORE_SFD 0x20000000 #define to_phy_device(__dev) container_of_const(to_mdio_device(__dev), struct phy_device, mdio) -- 2.51.0 From: Stefan Eichenberger If the PHY_F_KEEP_PREAMBLE_BEFORE_SFD flag is set in the phy_device::dev_flags field, the preamble will be kept before the start frame delimiter (SFD) on the KSZ9131 PHY. This flag is not officially documented by Micrel. However, information provided by NXP and Micrel indicates that this flag ensures the PHY sends the full preamble instead of removing it. The full discussion can be found on the NXP forum: https://community.nxp.com/t5/i-MX-Processors/iMX8MP-eqos-not-working-for-10base-t/m-p/2151032 Signed-off-by: Stefan Eichenberger --- drivers/net/phy/micrel.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c index 05de68b9f7191..a51bfe4a8d7b5 100644 --- a/drivers/net/phy/micrel.c +++ b/drivers/net/phy/micrel.c @@ -101,6 +101,14 @@ #define LAN8814_CABLE_DIAG_VCT_DATA_MASK GENMASK(7, 0) #define LAN8814_PAIR_BIT_SHIFT 12 +/* KSZ9x31 remote loopback register */ +#define KSZ9x31_REMOTE_LOOPBACK 0x11 +/* This is an undocumented bit of the KSZ9131RNX. + * It was reported by NXP in cooperation with Micrel. + */ +#define KSZ9x31_REMOTE_LOOPBACK_KEEP_PREAMBLE BIT(2) +#define KSZ9x31_REMOTE_LOOPBACK_EN BIT(8) + #define LAN8814_SKUS 0xB #define LAN8814_WIRE_PAIR_MASK 0xF @@ -1500,7 +1508,11 @@ static int ksz9131_config_init(struct phy_device *phydev) if (ret < 0) return ret; - return 0; + if (phydev->dev_flags & PHY_F_KEEP_PREAMBLE_BEFORE_SFD) + ret = phy_modify(phydev, KSZ9x31_REMOTE_LOOPBACK, 0, + KSZ9x31_REMOTE_LOOPBACK_KEEP_PREAMBLE); + + return ret; } #define MII_KSZ9131_AUTO_MDIX 0x1C -- 2.51.0 From: Stefan Eichenberger The stmmac implementation used by NXP for the i.MX8MP SoC is subject to errata ERR050694. According to this errata, when no preamble byte is transferred before the SFD from the PHY to the MAC, the MAC will discard the frame. Setting the PHY_F_KEEP_PREAMBLE_BEFORE_SFD flag instructs PHYs that support it to keep the preamble byte before the SFD. This ensures that the MAC successfully receives frames. As this is an issue in the MAC implementation, only enable the flag for the i.MX8MP SoC where the errata applies but not for other SoCs using a working stmmac implementation. The exact wording of the errata ERR050694 from NXP: The IEEE 802.3 standard states that, in MII/GMII modes, the byte preceding the SFD (0xD5), SMD-S (0xE6,0x4C, 0x7F, or 0xB3), or SMD-C (0x61, 0x52, 0x9E, or 0x2A) byte can be a non-PREAMBLE byte or there can be no preceding preamble byte. The MAC receiver must successfully receive a packet without any preamble(0x55) byte preceding the SFD, SMD-S, or SMD-C byte. However due to the defect, in configurations where frame preemption is enabled, when preamble byte does not precede the SFD, SMD-S, or SMD-C byte, the received packet is discarded by the MAC receiver. This is because, the start-of-packet detection logic of the MAC receiver incorrectly checks for a preamble byte. NXP refers to IEEE 802.3 where in clause 35.2.3.2.2 Receive case (GMII) they show two tables one where the preamble is preceding the SFD and one where it is not. The text says: The operation of 1000 Mb/s PHYs can result in shrinkage of the preamble between transmission at the source GMII and reception at the destination GMII. Table 35-3 depicts the case where no preamble bytes are conveyed across the GMII. This case may not be possible with a specific PHY, but illustrates the minimum preamble with which MAC shall be able to operate. Table 35-4 depicts the case where the entire preamble is conveyed across the GMII. This workaround was tested on a Verdin iMX8MP by enforcing 10 MBit/s: ethtool -s end0 speed 10 Without keeping the preamble, no packet were received. With keeping the preamble, everything worked as expected. Signed-off-by: Stefan Eichenberger --- drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c | 6 +++++- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 8 +++++++- include/linux/stmmac.h | 1 + 3 files changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c index db288fbd5a4df..c722ff2dc1fcb 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-imx.c @@ -320,6 +320,9 @@ static int imx_dwmac_probe(struct platform_device *pdev) if (data->flags & STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY) plat_dat->flags |= STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY; + if (data->flags & STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD) + plat_dat->flags |= STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD; + /* Default TX Q0 to use TSO and rest TXQ for TBS */ for (int i = 1; i < plat_dat->tx_queues_to_use; i++) plat_dat->tx_queues_cfg[i].tbs_en = 1; @@ -355,7 +358,8 @@ static struct imx_dwmac_ops imx8mp_dwmac_data = { .addr_width = 34, .mac_rgmii_txclk_auto_adj = false, .set_intf_mode = imx8mp_set_intf_mode, - .flags = STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY, + .flags = STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY | + STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD, }; static struct imx_dwmac_ops imx8dxl_dwmac_data = { diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index da206b24aaed9..08a6082fc0c02 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -1205,6 +1205,7 @@ static int stmmac_init_phy(struct net_device *dev) struct fwnode_handle *phy_fwnode; struct fwnode_handle *fwnode; struct ethtool_keee eee; + u32 dev_flags = 0; int ret; if (!phylink_expects_phy(priv->phylink)) @@ -1223,6 +1224,9 @@ static int stmmac_init_phy(struct net_device *dev) else phy_fwnode = NULL; + if (priv->plat->flags & STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD) + dev_flags |= PHY_F_KEEP_PREAMBLE_BEFORE_SFD; + /* Some DT bindings do not set-up the PHY handle. Let's try to * manually parse it */ @@ -1241,10 +1245,12 @@ static int stmmac_init_phy(struct net_device *dev) return -ENODEV; } + phydev->dev_flags |= dev_flags; + ret = phylink_connect_phy(priv->phylink, phydev); } else { fwnode_handle_put(phy_fwnode); - ret = phylink_fwnode_phy_connect(priv->phylink, fwnode, 0); + ret = phylink_fwnode_phy_connect(priv->phylink, fwnode, dev_flags); } if (ret) { diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h index f1054b9c2d8ac..e308c98c7bd33 100644 --- a/include/linux/stmmac.h +++ b/include/linux/stmmac.h @@ -191,6 +191,7 @@ enum dwmac_core_type { #define STMMAC_FLAG_EN_TX_LPI_CLOCKGATING BIT(11) #define STMMAC_FLAG_EN_TX_LPI_CLK_PHY_CAP BIT(12) #define STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY BIT(13) +#define STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD BIT(14) struct mac_device_info; -- 2.51.0