netdev - [PATCH net] net: pcs: xpcs: fix C73 AN not getting enabled

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Date: Tue, 16 May 2023 18:44:10 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: netdev@...r.kernel.org
Cc: Jose Abreu <Jose.Abreu@...opsys.com>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH net] net: pcs: xpcs: fix C73 AN not getting enabled

The XPCS expects clause 73 (copper backplane) autoneg to follow the
ethtool autoneg bit. It actually did that until the blamed
commit inaptly replaced state->an_enabled (coming from ethtool) with
phylink_autoneg_inband() (coming from the device tree or struct
phylink_config), as part of an unrelated phylink_pcs API conversion.

Russell King suggests that state->an_enabled from the original code was
just a proxy for the ethtool Autoneg bit, and that the correct way of
restoring the functionality is to check for this bit in the advertising
mask.

Fixes: 11059740e616 ("net: pcs: xpcs: convert to phylink_pcs_ops")
Link: https://lore.kernel.org/netdev/ZGNt2MFeRolKGFck@shell.armlinux.org.uk/
Suggested-by: Russell King (Oracle) <linux@...linux.org.uk>
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
The only (paranoid) test I've done is that the sja1105 driver (which
also calls xpcs_do_config() outside of phylink, and provides a NULL
pointer for "advertising") does not crash. Which was completely to be
expected, since none of the nxp_sja1105 XPCS compatible modes uses
DW_AN_C73.

 drivers/net/pcs/pcs-xpcs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index 539cd43eae8d..f680d03863ff 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -873,7 +873,7 @@ int xpcs_do_config(struct dw_xpcs *xpcs, phy_interface_t interface,
 
 	switch (compat->an_mode) {
 	case DW_AN_C73:
-		if (phylink_autoneg_inband(mode)) {
+		if (test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, advertising)) {
 			ret = xpcs_config_aneg_c73(xpcs, compat);
 			if (ret)
 				return ret;
-- 
2.34.1