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    Subject[PATCH v3 09/11] net: phylink: Adjust advertisement based on rate adaptation
    Date
    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@seco.com>
    ---

    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
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