[PATCH v3 09/11] net: phylink: Adjust advertisement based on rate adaptation

From: Sean Anderson
Date: Mon Jul 25 2022 - 11:39:45 EST


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@xxxxxxxx>
---

Changes in v3:
- Add phylink_cap_from_speed_duplex to look up the mac capability
corresponding to the interface's speed.
- Include RATE_ADAPT_CRS; it's a few lines and it doesn't hurt.

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

drivers/net/phy/phylink.c | 58 +++++++++++++++++++++++++++++++++++++--
include/linux/phylink.h | 3 +-
2 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 27b60a89ddc6..0eaca6f34413 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -456,14 +456,18 @@ static unsigned long phylink_cap_from_speed_duplex(int speed,
* 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)
{
+ int max_speed = phylink_interface_max_speed(interface);
unsigned long caps = MAC_SYM_PAUSE | MAC_ASYM_PAUSE;
+ unsigned long adapted_caps = 0;

switch (interface) {
case PHY_INTERFACE_MODE_USXGMII:
@@ -536,7 +540,53 @@ unsigned long phylink_get_capabilities(phy_interface_t interface,
break;
}

- return caps & mac_capabilities;
+ switch (rate_adaptation) {
+ case RATE_ADAPT_OPEN_LOOP:
+ /* TODO */
+ fallthrough;
+ case RATE_ADAPT_NONE:
+ adapted_caps = 0;
+ 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. This is because there's no way to
+ * accept pause frames without transmitting them if we only
+ * support symmetric pause.
+ */
+ if (!(mac_capabilities & MAC_SYM_PAUSE) ||
+ !(mac_capabilities & MAC_ASYM_PAUSE))
+ break;
+
+ /* We can't adapt if the MAC doesn't support the interface's
+ * max speed at full duplex.
+ */
+ if (mac_capabilities &
+ phylink_cap_from_speed_duplex(max_speed, DUPLEX_FULL)) {
+ /* Although a duplex-adapting phy might exist, we
+ * conservatively remove these modes because the MAC
+ * will not be aware of the half-duplex nature of the
+ * link.
+ */
+ adapted_caps = GENMASK(__fls(caps), __fls(MAC_10HD));
+ adapted_caps &= ~(MAC_1000HD | MAC_100HD | MAC_10HD);
+ }
+ break;
+ }
+ case RATE_ADAPT_CRS:
+ /* The MAC must support half duplex at the interface's max
+ * speed.
+ */
+ if (mac_capabilities &
+ phylink_cap_from_speed_duplex(max_speed, DUPLEX_HALF)) {
+ adapted_caps = GENMASK(__fls(caps), __fls(MAC_10HD));
+ adapted_caps &= mac_capabilities;
+ }
+ break;
+ }
+
+ return (caps & mac_capabilities) | adapted_caps;
}
EXPORT_SYMBOL_GPL(phylink_get_capabilities);

@@ -560,7 +610,8 @@ 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);
@@ -1586,6 +1637,7 @@ 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 192a18a8674a..265a344e1039 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -543,7 +543,8 @@ void phylink_caps_to_linkmodes(unsigned long *linkmodes, unsigned long caps);
int phylink_caps_find_max_speed(unsigned long caps, int *speed,
unsigned int *duplex);
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