From dbae3388ea9ca33bd1d5eabc3b0ef17e69c74677 Mon Sep 17 00:00:00 2001 From: "Russell King (Oracle)" Date: Tue, 23 Nov 2021 16:44:03 +0100 Subject: [PATCH] net: phylink: Force retrigger in case of latched link-fail indicator MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On mv88e6xxx 1G/2.5G PCS, the SerDes register 4.2001.2 has the following description: This register bit indicates when link was lost since the last read. For the current link status, read this register back-to-back. Thus to get current link state, we need to read the register twice. But doing that in the link change interrupt handler would lead to potentially ignoring link down events, which we really want to avoid. Thus this needs to be solved in phylink's resolve, by retriggering another resolve in the event when PCS reports link down and previous link was up, and by re-reading PCS state if the previous link was down. The wrong value is read when phylink requests change from sgmii to 2500base-x mode, and link won't come up. This fixes the bug. Fixes: 9525ae83959b ("phylink: add phylink infrastructure") Signed-off-by: Russell King (Oracle) Signed-off-by: Marek Behún Signed-off-by: Jakub Kicinski --- drivers/net/phy/phylink.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c index 708d2a984621..5904546acae6 100644 --- a/drivers/net/phy/phylink.c +++ b/drivers/net/phy/phylink.c @@ -741,6 +741,19 @@ static void phylink_resolve(struct work_struct *w) case MLO_AN_INBAND: phylink_mac_pcs_get_state(pl, &link_state); + /* The PCS may have a latching link-fail indicator. + * If the link was up, bring the link down and + * re-trigger the resolve. Otherwise, re-read the + * PCS state to get the current status of the link. + */ + if (!link_state.link) { + if (cur_link_state) + retrigger = true; + else + phylink_mac_pcs_get_state(pl, + &link_state); + } + /* If we have a phy, the "up" state is the union of * both the PHY and the MAC */