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Date:   Tue, 19 Jul 2022 19:49:58 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>
Cc:     Alexandru Marginean <alexandru.marginean@....com>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, Vladimir Oltean <olteanv@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sean Anderson <sean.anderson@...o.com>
Subject: [PATCH v2 08/11] net: phylink: Adjust advertisement based on rate adaptation

This adds support for adjusting the advertisement for pause-based rate
adaptation. This may result in a lossy link, since the final link settings
are not adjusted. Asymmetric pause support is necessary. It would be
possible for a MAC supporting only symmetric pause to use pause-based rate
adaptation, but only if pause reception was enabled as well.

Signed-off-by: Sean Anderson <sean.anderson@...o.com>
---

Changes in v2:
- Determine the interface speed and max mac speed directly instead of
  guessing based on the caps.

 drivers/net/phy/phylink.c | 87 +++++++++++++++++++++++++++++++++++++--
 include/linux/phylink.h   |  5 ++-
 2 files changed, 88 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 619ef553476f..f61040c93f3c 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -398,18 +398,65 @@ void phylink_caps_to_linkmodes(unsigned long *linkmodes, unsigned long caps)
 }
 EXPORT_SYMBOL_GPL(phylink_caps_to_linkmodes);
 
+static int phylink_caps_to_speed(unsigned long caps)
+{
+	unsigned int max_cap = __fls(caps);
+
+	if (max_cap == __fls(MAC_10HD) || max_cap == __fls(MAC_10FD))
+		return SPEED_10;
+	if (max_cap == __fls(MAC_100HD) || max_cap == __fls(MAC_100FD))
+		return SPEED_100;
+	if (max_cap == __fls(MAC_1000HD) || max_cap == __fls(MAC_1000FD))
+		return SPEED_1000;
+	if (max_cap == __fls(MAC_2500FD))
+		return SPEED_2500;
+	if (max_cap == __fls(MAC_5000FD))
+		return SPEED_5000;
+	if (max_cap == __fls(MAC_10000FD))
+		return SPEED_10000;
+	if (max_cap == __fls(MAC_20000FD))
+		return SPEED_20000;
+	if (max_cap == __fls(MAC_25000FD))
+		return SPEED_25000;
+	if (max_cap == __fls(MAC_40000FD))
+		return SPEED_40000;
+	if (max_cap == __fls(MAC_50000FD))
+		return SPEED_50000;
+	if (max_cap == __fls(MAC_56000FD))
+		return SPEED_56000;
+	if (max_cap == __fls(MAC_100000FD))
+		return SPEED_100000;
+	if (max_cap == __fls(MAC_200000FD))
+		return SPEED_200000;
+	if (max_cap == __fls(MAC_400000FD))
+		return SPEED_400000;
+	return SPEED_UNKNOWN;
+}
+
 /**
  * phylink_get_capabilities() - get capabilities for a given MAC
  * @interface: phy interface mode defined by &typedef phy_interface_t
  * @mac_capabilities: bitmask of MAC capabilities
+ * @rate_adaptation: type of rate adaptation being performed
  *
  * Get the MAC capabilities that are supported by the @interface mode and
  * @mac_capabilities.
  */
 unsigned long phylink_get_capabilities(phy_interface_t interface,
-				       unsigned long mac_capabilities)
+				       unsigned long mac_capabilities,
+				       int rate_adaptation)
 {
 	unsigned long caps = MAC_SYM_PAUSE | MAC_ASYM_PAUSE;
+	unsigned long adapted_caps = 0;
+	struct phylink_link_state state = {
+		.interface = interface,
+		.rate_adaptation = rate_adaptation,
+		.link_speed = SPEED_UNKNOWN,
+		.link_duplex = DUPLEX_UNKNOWN,
+	};
+
+	/* Look up the interface speed */
+	phylink_state_fill_speed_duplex(&state);
 
 	switch (interface) {
 	case PHY_INTERFACE_MODE_USXGMII:
@@ -482,7 +529,39 @@ unsigned long phylink_get_capabilities(phy_interface_t interface,
 		break;
 	}
 
-	return caps & mac_capabilities;
+	switch (rate_adaptation) {
+	case RATE_ADAPT_NONE:
+		break;
+	case RATE_ADAPT_PAUSE: {
+		/* The MAC must support asymmetric pause towards the local
+		 * device for this. We could allow just symmetric pause, but
+		 * then we might have to renegotiate if the link partner
+		 * doesn't support pause.
+		 */
+		if (!(mac_capabilities & MAC_SYM_PAUSE) ||
+		    !(mac_capabilities & MAC_ASYM_PAUSE))
+			break;
+
+		/* Can't adapt if the MAC doesn't support the interface's max
+		 * speed
+		 */
+		if (state.speed != phylink_caps_to_speed(mac_capabilities))
+			break;
+
+		adapted_caps = GENMASK(__fls(caps), __fls(MAC_10HD));
+		/* We can't use pause frames in half-duplex mode */
+		adapted_caps &= ~(MAC_1000HD | MAC_100HD | MAC_10HD);
+		break;
+	}
+	case RATE_ADAPT_CRS:
+		/* TODO */
+		break;
+	case RATE_ADAPT_OPEN_LOOP:
+		/* TODO */
+		break;
+	}
+
+	return (caps & mac_capabilities) | adapted_caps;
 }
 EXPORT_SYMBOL_GPL(phylink_get_capabilities);
 
@@ -506,7 +585,8 @@ void phylink_generic_validate(struct phylink_config *config,
 	phylink_set_port_modes(mask);
 	phylink_set(mask, Autoneg);
 	caps = phylink_get_capabilities(state->interface,
-					config->mac_capabilities);
+					config->mac_capabilities,
+					state->rate_adaptation);
 	phylink_caps_to_linkmodes(mask, caps);
 
 	linkmode_and(supported, supported, mask);
@@ -1529,6 +1609,7 @@ static int phylink_bringup_phy(struct phylink *pl, struct phy_device *phy,
 		config.interface = PHY_INTERFACE_MODE_NA;
 	else
 		config.interface = interface;
+	config.rate_adaptation = phy_get_rate_adaptation(phy, config.interface);
 
 	ret = phylink_validate(pl, supported, &config);
 	if (ret) {
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index f32b97f27ddc..73e1aa73e30f 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -70,6 +70,8 @@ static inline bool phylink_autoneg_inband(unsigned int mode)
  * @link: true if the link is up.
  * @an_enabled: true if autonegotiation is enabled/desired.
  * @an_complete: true if autonegotiation has completed.
+ * @rate_adaptation: method of throttling @interface_speed to @speed, one of
+ *   RATE_ADAPT_* constants.
  */
 struct phylink_link_state {
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(advertising);
@@ -531,7 +533,8 @@ void pcs_link_up(struct phylink_pcs *pcs, unsigned int mode,
 
 void phylink_caps_to_linkmodes(unsigned long *linkmodes, unsigned long caps);
 unsigned long phylink_get_capabilities(phy_interface_t interface,
-				       unsigned long mac_capabilities);
+				       unsigned long mac_capabilities,
+				       int rate_adaptation);
 void phylink_generic_validate(struct phylink_config *config,
 			      unsigned long *supported,
 			      struct phylink_link_state *state);
-- 
2.35.1.1320.gc452695387.dirty

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