--- /dev/null
+From 0c3e10cb44232833a50cb8e3e784c432906a60c1 Mon Sep 17 00:00:00 2001
+From: Sean Anderson <sean.anderson@seco.com>
+Date: Tue, 20 Sep 2022 18:12:31 -0400
+Subject: [PATCH] net: phy: Add support for rate matching
+
+This adds support for rate matching (also known as rate adaptation) to
+the phy subsystem. The general idea is that the phy interface runs at
+one speed, and the MAC throttles the rate at which it sends packets to
+the link speed. There's a good overview of several techniques for
+achieving this at [1]. This patch adds support for three: pause-frame
+based (such as in Aquantia phys), CRS-based (such as in 10PASS-TS and
+2BASE-TL), and open-loop-based (such as in 10GBASE-W).
+
+This patch makes a few assumptions and a few non assumptions about the
+types of rate matching available. First, it assumes that different phys
+may use different forms of rate matching. Second, it assumes that phys
+can use rate matching for any of their supported link speeds (e.g. if a
+phy supports 10BASE-T and XGMII, then it can adapt XGMII to 10BASE-T).
+Third, it does not assume that all interface modes will use the same
+form of rate matching. Fourth, it does not assume that all phy devices
+will support rate matching (even if some do). Relaxing or strengthening
+these (non-)assumptions could result in a different API. For example, if
+all interface modes were assumed to use the same form of rate matching,
+then a bitmask of interface modes supportting rate matching would
+suffice.
+
+For some better visibility into the process, the current rate matching
+mode is exposed as part of the ethtool ksettings. For the moment, only
+read access is supported. I'm not sure what userspace might want to
+configure yet (disable it altogether, disable just one mode, specify the
+mode to use, etc.). For the moment, since only pause-based rate
+adaptation support is added in the next few commits, rate matching can
+be disabled altogether by adjusting the advertisement.
+
+802.3 calls this feature "rate adaptation" in clause 49 (10GBASE-R) and
+"rate matching" in clause 61 (10PASS-TL and 2BASE-TS). Aquantia also calls
+this feature "rate adaptation". I chose "rate matching" because it is
+shorter, and because Russell doesn't think "adaptation" is correct in this
+context.
+
+Signed-off-by: Sean Anderson <sean.anderson@seco.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ Documentation/networking/ethtool-netlink.rst | 2 ++
+ drivers/net/phy/phy-core.c | 21 +++++++++++++++
+ drivers/net/phy/phy.c | 28 ++++++++++++++++++++
+ include/linux/phy.h | 22 ++++++++++++++-
+ include/uapi/linux/ethtool.h | 18 +++++++++++--
+ include/uapi/linux/ethtool_netlink.h | 1 +
+ net/ethtool/ioctl.c | 1 +
+ net/ethtool/linkmodes.c | 5 ++++
+ 8 files changed, 95 insertions(+), 3 deletions(-)
+
+--- a/Documentation/networking/ethtool-netlink.rst
++++ b/Documentation/networking/ethtool-netlink.rst
+@@ -418,6 +418,7 @@ Kernel response contents:
+ ``ETHTOOL_A_LINKMODES_DUPLEX`` u8 duplex mode
+ ``ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG`` u8 Master/slave port mode
+ ``ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE`` u8 Master/slave port state
++ ``ETHTOOL_A_LINKMODES_RATE_MATCHING`` u8 PHY rate matching
+ ========================================== ====== ==========================
+
+ For ``ETHTOOL_A_LINKMODES_OURS``, value represents advertised modes and mask
+@@ -441,6 +442,7 @@ Request contents:
+ ``ETHTOOL_A_LINKMODES_SPEED`` u32 link speed (Mb/s)
+ ``ETHTOOL_A_LINKMODES_DUPLEX`` u8 duplex mode
+ ``ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG`` u8 Master/slave port mode
++ ``ETHTOOL_A_LINKMODES_RATE_MATCHING`` u8 PHY rate matching
+ ``ETHTOOL_A_LINKMODES_LANES`` u32 lanes
+ ========================================== ====== ==========================
+
+--- a/drivers/net/phy/phy-core.c
++++ b/drivers/net/phy/phy-core.c
+@@ -75,6 +75,27 @@ const char *phy_duplex_to_str(unsigned i
+ EXPORT_SYMBOL_GPL(phy_duplex_to_str);
+
+ /**
++ * phy_rate_matching_to_str - Return a string describing the rate matching
++ *
++ * @rate_matching: Type of rate matching to describe
++ */
++const char *phy_rate_matching_to_str(int rate_matching)
++{
++ switch (rate_matching) {
++ case RATE_MATCH_NONE:
++ return "none";
++ case RATE_MATCH_PAUSE:
++ return "pause";
++ case RATE_MATCH_CRS:
++ return "crs";
++ case RATE_MATCH_OPEN_LOOP:
++ return "open-loop";
++ }
++ return "Unsupported (update phy-core.c)";
++}
++EXPORT_SYMBOL_GPL(phy_rate_matching_to_str);
++
++/**
+ * phy_interface_num_ports - Return the number of links that can be carried by
+ * a given MAC-PHY physical link. Returns 0 if this is
+ * unknown, the number of links else.
+--- a/drivers/net/phy/phy.c
++++ b/drivers/net/phy/phy.c
+@@ -127,6 +127,33 @@ void phy_print_status(struct phy_device
+ EXPORT_SYMBOL(phy_print_status);
+
+ /**
++ * phy_get_rate_matching - determine if rate matching is supported
++ * @phydev: The phy device to return rate matching for
++ * @iface: The interface mode to use
++ *
++ * This determines the type of rate matching (if any) that @phy supports
++ * using @iface. @iface may be %PHY_INTERFACE_MODE_NA to determine if any
++ * interface supports rate matching.
++ *
++ * Return: The type of rate matching @phy supports for @iface, or
++ * %RATE_MATCH_NONE.
++ */
++int phy_get_rate_matching(struct phy_device *phydev,
++ phy_interface_t iface)
++{
++ int ret = RATE_MATCH_NONE;
++
++ if (phydev->drv->get_rate_matching) {
++ mutex_lock(&phydev->lock);
++ ret = phydev->drv->get_rate_matching(phydev, iface);
++ mutex_unlock(&phydev->lock);
++ }
++
++ return ret;
++}
++EXPORT_SYMBOL_GPL(phy_get_rate_matching);
++
++/**
+ * phy_config_interrupt - configure the PHY device for the requested interrupts
+ * @phydev: the phy_device struct
+ * @interrupts: interrupt flags to configure for this @phydev
+@@ -268,6 +295,7 @@ void phy_ethtool_ksettings_get(struct ph
+ cmd->base.duplex = phydev->duplex;
+ cmd->base.master_slave_cfg = phydev->master_slave_get;
+ cmd->base.master_slave_state = phydev->master_slave_state;
++ cmd->base.rate_matching = phydev->rate_matching;
+ if (phydev->interface == PHY_INTERFACE_MODE_MOCA)
+ cmd->base.port = PORT_BNC;
+ else
+--- a/include/linux/phy.h
++++ b/include/linux/phy.h
+@@ -280,7 +280,6 @@ static inline const char *phy_modes(phy_
+ }
+ }
+
+-
+ #define PHY_INIT_TIMEOUT 100000
+ #define PHY_FORCE_TIMEOUT 10
+
+@@ -573,6 +572,7 @@ struct macsec_ops;
+ * @lp_advertising: Current link partner advertised linkmodes
+ * @eee_broken_modes: Energy efficient ethernet modes which should be prohibited
+ * @autoneg: Flag autoneg being used
++ * @rate_matching: Current rate matching mode
+ * @link: Current link state
+ * @autoneg_complete: Flag auto negotiation of the link has completed
+ * @mdix: Current crossover
+@@ -639,6 +639,8 @@ struct phy_device {
+ unsigned irq_suspended:1;
+ unsigned irq_rerun:1;
+
++ int rate_matching;
++
+ enum phy_state state;
+
+ u32 dev_flags;
+@@ -801,6 +803,21 @@ struct phy_driver {
+ */
+ int (*get_features)(struct phy_device *phydev);
+
++ /**
++ * @get_rate_matching: Get the supported type of rate matching for a
++ * particular phy interface. This is used by phy consumers to determine
++ * whether to advertise lower-speed modes for that interface. It is
++ * assumed that if a rate matching mode is supported on an interface,
++ * then that interface's rate can be adapted to all slower link speeds
++ * supported by the phy. If iface is %PHY_INTERFACE_MODE_NA, and the phy
++ * supports any kind of rate matching for any interface, then it must
++ * return that rate matching mode (preferring %RATE_MATCH_PAUSE to
++ * %RATE_MATCH_CRS). If the interface is not supported, this should
++ * return %RATE_MATCH_NONE.
++ */
++ int (*get_rate_matching)(struct phy_device *phydev,
++ phy_interface_t iface);
++
+ /* PHY Power Management */
+ /** @suspend: Suspend the hardware, saving state if needed */
+ int (*suspend)(struct phy_device *phydev);
+@@ -967,6 +984,7 @@ struct phy_fixup {
+
+ const char *phy_speed_to_str(int speed);
+ const char *phy_duplex_to_str(unsigned int duplex);
++const char *phy_rate_matching_to_str(int rate_matching);
+
+ int phy_interface_num_ports(phy_interface_t interface);
+
+@@ -1675,6 +1693,8 @@ int phy_disable_interrupts(struct phy_de
+ void phy_request_interrupt(struct phy_device *phydev);
+ void phy_free_interrupt(struct phy_device *phydev);
+ void phy_print_status(struct phy_device *phydev);
++int phy_get_rate_matching(struct phy_device *phydev,
++ phy_interface_t iface);
+ int phy_set_max_speed(struct phy_device *phydev, u32 max_speed);
+ void phy_remove_link_mode(struct phy_device *phydev, u32 link_mode);
+ void phy_advertise_supported(struct phy_device *phydev);
+--- a/include/uapi/linux/ethtool.h
++++ b/include/uapi/linux/ethtool.h
+@@ -1809,6 +1809,20 @@ static inline int ethtool_validate_duple
+ #define MASTER_SLAVE_STATE_SLAVE 3
+ #define MASTER_SLAVE_STATE_ERR 4
+
++/* These are used to throttle the rate of data on the phy interface when the
++ * native speed of the interface is higher than the link speed. These should
++ * not be used for phy interfaces which natively support multiple speeds (e.g.
++ * MII or SGMII).
++ */
++/* No rate matching performed. */
++#define RATE_MATCH_NONE 0
++/* The phy sends pause frames to throttle the MAC. */
++#define RATE_MATCH_PAUSE 1
++/* The phy asserts CRS to prevent the MAC from transmitting. */
++#define RATE_MATCH_CRS 2
++/* The MAC is programmed with a sufficiently-large IPG. */
++#define RATE_MATCH_OPEN_LOOP 3
++
+ /* Which connector port. */
+ #define PORT_TP 0x00
+ #define PORT_AUI 0x01
+@@ -2002,8 +2016,8 @@ enum ethtool_reset_flags {
+ * reported consistently by PHYLIB. Read-only.
+ * @master_slave_cfg: Master/slave port mode.
+ * @master_slave_state: Master/slave port state.
++ * @rate_matching: Rate adaptation performed by the PHY
+ * @reserved: Reserved for future use; see the note on reserved space.
+- * @reserved1: Reserved for future use; see the note on reserved space.
+ * @link_mode_masks: Variable length bitmaps.
+ *
+ * If autonegotiation is disabled, the speed and @duplex represent the
+@@ -2054,7 +2068,7 @@ struct ethtool_link_settings {
+ __u8 transceiver;
+ __u8 master_slave_cfg;
+ __u8 master_slave_state;
+- __u8 reserved1[1];
++ __u8 rate_matching;
+ __u32 reserved[7];
+ __u32 link_mode_masks[0];
+ /* layout of link_mode_masks fields:
+--- a/include/uapi/linux/ethtool_netlink.h
++++ b/include/uapi/linux/ethtool_netlink.h
+@@ -238,6 +238,7 @@ enum {
+ ETHTOOL_A_LINKMODES_MASTER_SLAVE_CFG, /* u8 */
+ ETHTOOL_A_LINKMODES_MASTER_SLAVE_STATE, /* u8 */
+ ETHTOOL_A_LINKMODES_LANES, /* u32 */
++ ETHTOOL_A_LINKMODES_RATE_MATCHING, /* u8 */
+
+ /* add new constants above here */
+ __ETHTOOL_A_LINKMODES_CNT,
+--- a/net/ethtool/ioctl.c
++++ b/net/ethtool/ioctl.c
+@@ -559,6 +559,7 @@ static int ethtool_get_link_ksettings(st
+ = __ETHTOOL_LINK_MODE_MASK_NU32;
+ link_ksettings.base.master_slave_cfg = MASTER_SLAVE_CFG_UNSUPPORTED;
+ link_ksettings.base.master_slave_state = MASTER_SLAVE_STATE_UNSUPPORTED;
++ link_ksettings.base.rate_matching = RATE_MATCH_NONE;
+
+ return store_link_ksettings_for_user(useraddr, &link_ksettings);
+ }
+--- a/net/ethtool/linkmodes.c
++++ b/net/ethtool/linkmodes.c
+@@ -70,6 +70,7 @@ static int linkmodes_reply_size(const st
+ + nla_total_size(sizeof(u32)) /* LINKMODES_SPEED */
+ + nla_total_size(sizeof(u32)) /* LINKMODES_LANES */
+ + nla_total_size(sizeof(u8)) /* LINKMODES_DUPLEX */
++ + nla_total_size(sizeof(u8)) /* LINKMODES_RATE_MATCHING */
+ + 0;
+ ret = ethnl_bitset_size(ksettings->link_modes.advertising,
+ ksettings->link_modes.supported,
+@@ -143,6 +144,10 @@ static int linkmodes_fill_reply(struct s
+ lsettings->master_slave_state))
+ return -EMSGSIZE;
+
++ if (nla_put_u8(skb, ETHTOOL_A_LINKMODES_RATE_MATCHING,
++ lsettings->rate_matching))
++ return -EMSGSIZE;
++
+ return 0;
+ }
+
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