This UAPI is needed for BroadR-Reach 100BASE-T1 devices. Due to lack of
auto-negotiation support, we needed to be able to configure the
MASTER-SLAVE role of the port manually or from an application in user
space.

The same UAPI can be used for 1000BASE-T or MultiGBASE-T devices to
force MASTER or SLAVE role. See IEEE 802.3-2018:
22.2.4.3.7 MASTER-SLAVE control register (Register 9)
22.2.4.3.8 MASTER-SLAVE status register (Register 10)
40.5.2 MASTER-SLAVE configuration resolution
45.2.1.185.1 MASTER-SLAVE config value (1.2100.14)
45.2.7.10 MultiGBASE-T AN control 1 register (Register 7.32)

The MASTER-SLAVE role affects the clock configuration:

-------------------------------------------------------------------------------
When the  PHY is configured as MASTER, the PMA Transmit function shall
source TX_TCLK from a local clock source. When configured as SLAVE, the
PMA Transmit function shall source TX_TCLK from the clock recovered from
data stream provided by MASTER.

iMX6Q                     KSZ9031                XXX
------\                /-----------\        /------------\
      |                |           |        |            |
 MAC  |<----RGMII----->| PHY Slave |<------>| PHY Master |
      |<--- 125 MHz ---+-<------/  |        | \          |
------/                \-----------/        \------------/
                                               ^
                                                \-TX_TCLK

-------------------------------------------------------------------------------

Since some clock or link related issues are only reproducible in a
specific MASTER-SLAVE-role, MAC and PHY configuration, it is beneficial
to provide generic (not 100BASE-T1 specific) interface to the user space
for configuration flexibility and trouble shooting.

Signed-off-by: Oleksij Rempel <o.rem...@pengutronix.de>
---
 netlink/desc-ethtool.c       |  2 ++
 netlink/settings.c           | 50 ++++++++++++++++++++++++++++++++++++
 uapi/linux/ethtool.h         | 11 ++++++++
 uapi/linux/ethtool_netlink.h |  2 ++
 4 files changed, 65 insertions(+)

diff --git a/netlink/desc-ethtool.c b/netlink/desc-ethtool.c
index 76c6f13..b0a793c 100644
--- a/netlink/desc-ethtool.c
+++ b/netlink/desc-ethtool.c
@@ -85,6 +85,8 @@ static const struct pretty_nla_desc __linkmodes_desc[] = {
        NLATTR_DESC_NESTED(ETHTOOL_A_LINKMODES_PEER, bitset),
        NLATTR_DESC_U32(ETHTOOL_A_LINKMODES_SPEED),
        NLATTR_DESC_U8(ETHTOOL_A_LINKMODES_DUPLEX),
+       NLATTR_DESC_U8(ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG),
+       NLATTR_DESC_U8(ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE),
 };
 
 static const struct pretty_nla_desc __linkstate_desc[] = {
diff --git a/netlink/settings.c b/netlink/settings.c
index 8be5a22..76ca862 100644
--- a/netlink/settings.c
+++ b/netlink/settings.c
@@ -37,6 +37,21 @@ static const char *const names_duplex[] = {
        [DUPLEX_FULL]           = "Full",
 };
 
+static const char *const names_master_slave_state[] = {
+       [PORT_MODE_STATE_UNKNOWN]       = "Unknown",
+       [PORT_MODE_STATE_MASTER]        = "Master",
+       [PORT_MODE_STATE_SLAVE]         = "Slave",
+       [PORT_MODE_STATE_ERR]           = "Resolution error",
+};
+
+static const char *const names_master_slave_cfg[] = {
+       [PORT_MODE_CFG_UNKNOWN]                 = "Unknown",
+       [PORT_MODE_CFG_MASTER_PREFERRED]        = "preferred Master",
+       [PORT_MODE_CFG_SLAVE_PREFERRED]         = "preferred Slave",
+       [PORT_MODE_CFG_MASTER_FORCE]            = "forced Master",
+       [PORT_MODE_CFG_SLAVE_FORCE]             = "forced Slave",
+};
+
 static const char *const names_port[] = {
        [PORT_TP]               = "Twisted Pair",
        [PORT_AUI]              = "AUI",
@@ -520,6 +535,25 @@ int linkmodes_reply_cb(const struct nlmsghdr *nlhdr, void 
*data)
                printf("\tAuto-negotiation: %s\n",
                       (autoneg == AUTONEG_DISABLE) ? "off" : "on");
        }
+       if (tb[ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG]) {
+               uint8_t val;
+
+               val = mnl_attr_get_u8(tb[ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG]);
+
+               print_banner(nlctx);
+               print_enum(names_master_slave_cfg,
+                          ARRAY_SIZE(names_master_slave_cfg), val,
+                          "Port mode cfg");
+       }
+       if (tb[ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE]) {
+               uint8_t val;
+
+               val = 
mnl_attr_get_u8(tb[ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE]);
+               print_banner(nlctx);
+               print_enum(names_master_slave_state,
+                          ARRAY_SIZE(names_master_slave_state), val,
+                          "Port mode status");
+       }
 
        return MNL_CB_OK;
 err:
@@ -827,6 +861,14 @@ static const struct lookup_entry_u32 duplex_values[] = {
        {}
 };
 
+static const struct lookup_entry_u32 master_slave_values[] = {
+       { .arg = "master-preferred",    .val = PORT_MODE_CFG_MASTER_PREFERRED },
+       { .arg = "slave-preferred",     .val = PORT_MODE_CFG_SLAVE_PREFERRED },
+       { .arg = "master-force",        .val = PORT_MODE_CFG_MASTER_FORCE },
+       { .arg = "slave-force",         .val = PORT_MODE_CFG_SLAVE_FORCE },
+       {}
+};
+
 char wol_bit_chars[WOL_MODE_COUNT] = {
        [WAKE_PHY_BIT]          = 'p',
        [WAKE_UCAST_BIT]        = 'u',
@@ -917,6 +959,14 @@ static const struct param_parser sset_params[] = {
                .handler_data   = duplex_values,
                .min_argc       = 1,
        },
+       {
+               .arg            = "master-slave",
+               .group          = ETHTOOL_MSG_LINKMODES_SET,
+               .type           = ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG,
+               .handler        = nl_parse_lookup_u8,
+               .handler_data   = master_slave_values,
+               .min_argc       = 1,
+       },
        {
                .arg            = "wol",
                .group          = ETHTOOL_MSG_WOL_SET,
diff --git a/uapi/linux/ethtool.h b/uapi/linux/ethtool.h
index d3dcb45..d2872f9 100644
--- a/uapi/linux/ethtool.h
+++ b/uapi/linux/ethtool.h
@@ -1659,6 +1659,17 @@ static __inline__ int ethtool_validate_duplex(__u8 
duplex)
        return 0;
 }
 
+/* Port mode */
+#define PORT_MODE_CFG_UNKNOWN          1
+#define PORT_MODE_CFG_MASTER_PREFERRED 2
+#define PORT_MODE_CFG_SLAVE_PREFERRED  3
+#define PORT_MODE_CFG_MASTER_FORCE     4
+#define PORT_MODE_CFG_SLAVE_FORCE      5
+#define PORT_MODE_STATE_UNKNOWN                1
+#define PORT_MODE_STATE_MASTER         2
+#define PORT_MODE_STATE_SLAVE          3
+#define PORT_MODE_STATE_ERR            4
+
 /* Which connector port. */
 #define PORT_TP                        0x00
 #define PORT_AUI               0x01
diff --git a/uapi/linux/ethtool_netlink.h b/uapi/linux/ethtool_netlink.h
index ad6d3a0..73a720c 100644
--- a/uapi/linux/ethtool_netlink.h
+++ b/uapi/linux/ethtool_netlink.h
@@ -185,6 +185,8 @@ enum {
        ETHTOOL_A_LINKMODES_PEER,               /* bitset */
        ETHTOOL_A_LINKMODES_SPEED,              /* u32 */
        ETHTOOL_A_LINKMODES_DUPLEX,             /* u8 */
+       ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG,   /* u8 */
+       ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE, /* u8 */
 
        /* add new constants above here */
        __ETHTOOL_A_LINKMODES_CNT,
-- 
2.26.2

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