kernel: fix DSA mac_select_pcs backport

Backport commit from Linux 5.18 fixing phylink with DSA drivers which
do not provide mac_select_pcs yet.

Fixes: aab466f422 ("kernel: backport generic phylink validate")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

diff --git a/target/linux/generic/backport-5.15/703-15-v5.18-net-phy-phylink-fix-DSA-mac_select_pcs-introduction.patch b/target/linux/generic/backport-5.15/703-15-v5.18-net-phy-phylink-fix-DSA-mac_select_pcs-introduction.patch
new file mode 100644 (file)
index 0000000..4ab90fa
--- /dev/null
+++ b/target/linux/generic/backport-5.15/703-15-v5.18-net-phy-phylink-fix-DSA-mac_select_pcs-introduction.patch
@@ -0,0 +1,88 @@
+From 1054457006d4a14de4ae4132030e33d7eedaeba1 Mon Sep 17 00:00:00 2001
+From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
+Date: Mon, 21 Feb 2022 17:10:52 +0000
+Subject: [PATCH] net: phy: phylink: fix DSA mac_select_pcs() introduction
+
+Vladimir Oltean reports that probing on DSA drivers that aren't yet
+populating supported_interfaces now fails. Fix this by allowing
+phylink to detect whether DSA actually provides an underlying
+mac_select_pcs() implementation.
+
+Reported-by: Vladimir Oltean <olteanv@gmail.com>
+Fixes: bde018222c6b ("net: dsa: add support for phylink mac_select_pcs()")
+Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
+Tested-by: Vladimir Oltean <olteanv@gmail.com>
+Link: https://lore.kernel.org/r/E1nMCD6-00A0wC-FG@rmk-PC.armlinux.org.uk
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+---
+ drivers/net/phy/phylink.c | 14 +++++++++++---
+ net/dsa/port.c            |  2 +-
+ 2 files changed, 12 insertions(+), 4 deletions(-)
+
+--- a/drivers/net/phy/phylink.c
++++ b/drivers/net/phy/phylink.c
+@@ -74,6 +74,7 @@ struct phylink {
+       struct work_struct resolve;
+ 
+       bool mac_link_dropped;
++      bool using_mac_select_pcs;
+ 
+       struct sfp_bus *sfp_bus;
+       bool sfp_may_have_phy;
+@@ -163,7 +164,7 @@ static int phylink_validate_mac_and_pcs(
+       int ret;
+ 
+       /* Get the PCS for this interface mode */
+-      if (pl->mac_ops->mac_select_pcs) {
++      if (pl->using_mac_select_pcs) {
+               pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
+               if (IS_ERR(pcs))
+                       return PTR_ERR(pcs);
+@@ -790,7 +791,7 @@ static void phylink_major_config(struct
+ 
+       phylink_dbg(pl, "major config %s\n", phy_modes(state->interface));
+ 
+-      if (pl->mac_ops->mac_select_pcs) {
++      if (pl->using_mac_select_pcs) {
+               pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
+               if (IS_ERR(pcs)) {
+                       phylink_err(pl,
+@@ -1192,11 +1193,17 @@ struct phylink *phylink_create(struct ph
+                              phy_interface_t iface,
+                              const struct phylink_mac_ops *mac_ops)
+ {
++      bool using_mac_select_pcs = false;
+       struct phylink *pl;
+       int ret;
+ 
+-      /* Validate the supplied configuration */
+       if (mac_ops->mac_select_pcs &&
++          mac_ops->mac_select_pcs(config, PHY_INTERFACE_MODE_NA) !=
++            ERR_PTR(-EOPNOTSUPP))
++              using_mac_select_pcs = true;
++
++      /* Validate the supplied configuration */
++      if (using_mac_select_pcs &&
+           phy_interface_empty(config->supported_interfaces)) {
+               dev_err(config->dev,
+                       "phylink: error: empty supported_interfaces but mac_select_pcs() method present\n");
+@@ -1220,6 +1227,7 @@ struct phylink *phylink_create(struct ph
+               return ERR_PTR(-EINVAL);
+       }
+ 
++      pl->using_mac_select_pcs = using_mac_select_pcs;
+       pl->phy_state.interface = iface;
+       pl->link_interface = iface;
+       if (iface == PHY_INTERFACE_MODE_MOCA)
+--- a/net/dsa/port.c
++++ b/net/dsa/port.c
+@@ -1017,8 +1017,8 @@ dsa_port_phylink_mac_select_pcs(struct p
+                               phy_interface_t interface)
+ {
+       struct dsa_port *dp = container_of(config, struct dsa_port, pl_config);
++      struct phylink_pcs *pcs = ERR_PTR(-EOPNOTSUPP);
+       struct dsa_switch *ds = dp->ds;
+-      struct phylink_pcs *pcs = NULL;
+ 
+       if (ds->ops->phylink_mac_select_pcs)
+               pcs = ds->ops->phylink_mac_select_pcs(ds, dp->index, interface);