ath79: fix link mode support list on UniFi AC

This fixes incorrect supported link modes indicated when using ethtool
on the Ubiquiti UniFi AC lite / LR / Mesh.

eroot@OpenWrt:~# ethtool eth0
Settings for eth0:
	Supported ports: [ TP MII ]
	Supported link modes:   100baseT/Half 100baseT/Full
	                        1000baseT/Full
	                        1000baseX/Full

The reason for this is, that since kernel 5.4 the PHY capabilities are
read dynamically from the PHY. As Ubiquiti leaves the PHY in a wrong
state, the capabilities of the SGMII side of the PHY are read.

As a side effect, 10 Mbit/s link modes did not work on these boards.

Signed-off-by: David Bauer <[email protected]>

target/linux/generic/pending-5.10/736-net-phy-at803x-add-at8031-features.patch

@@ -0,0 +1,36 @@
+Add back explicit PHY feature flags for the AR8031 and
+AR8033 PHY instead of reading them from the PHY.
+
+The Botloader for Ubiquiti UniFi AC boards (and possibly more)
+leave fiber page selected, thus we will end up reading the PHY
+capabilities of the SGMII side (which does not offer 10 Mbit/s).
+
+We already have a hack in place, which switches back to the copper
+page, however this happens after capabilities are read.
+
+The original conversation about 735-net-phy-at803x-fix-at8033-sgmii-mode
+back in 2015 explicitly mention the UniFi AC Lite. The issue however is
+not missing autonegotiation on the Fiber side, but the fact the PHY
+is never switched to the copper side. So half of this patch is superfluous.
+
+A fix is currently being upstreamed. Once this is mainlined and available to us,
+these patches can be dropped:
+
+735-net-phy-at803x-fix-at8033-sgmii-mode.patch
+736-net-phy-at803x-add-at8031-features.patch
+
+This was tested on a UniFi AC Lite.
+
+See https://patchwork.kernel.org/project/netdevbpf/list/?series=467341
+
+--- a/drivers/net/phy/at803x.c
++++ b/drivers/net/phy/at803x.c
+@@ -1119,7 +1119,7 @@ static struct phy_driver at803x_driver[]
+ 	.get_wol		= at803x_get_wol,
+ 	.suspend		= at803x_suspend,
+ 	.resume			= at803x_resume,
+-	/* PHY_GBIT_FEATURES */
++	.features               = PHY_GBIT_FEATURES,
+ 	.read_status		= at803x_read_status,
+ 	.aneg_done		= at803x_aneg_done,
+ 	.ack_interrupt		= &at803x_ack_interrupt,

target/linux/generic/pending-5.4/736-net-phy-at803x-add-at8031-features.patch

@@ -0,0 +1,36 @@
+Add back explicit PHY feature flags for the AR8031 and
+AR8033 PHY instead of reading them from the PHY.
+
+The Botloader for Ubiquiti UniFi AC boards (and possibly more)
+leave fiber page selected, thus we will end up reading the PHY
+capabilities of the SGMII side (which does not offer 10 Mbit/s).
+
+We already have a hack in place, which switches back to the copper
+page, however this happens after capabilities are read.
+
+The original conversation about 735-net-phy-at803x-fix-at8033-sgmii-mode
+back in 2015 explicitly mention the UniFi AC Lite. The issue however is
+not missing autonegotiation on the Fiber side, but the fact the PHY
+is never switched to the copper side. So half of this patch is superfluous.
+
+A fix is currently being upstreamed. Once this is mainlined and available to us,
+these patches can be dropped:
+
+735-net-phy-at803x-fix-at8033-sgmii-mode.patch
+736-net-phy-at803x-add-at8031-features.patch
+
+This was tested on a UniFi AC Lite.
+
+See https://patchwork.kernel.org/project/netdevbpf/list/?series=467341
+
+--- a/drivers/net/phy/at803x.c
++++ b/drivers/net/phy/at803x.c
+@@ -490,7 +490,7 @@ static struct phy_driver at803x_driver[]
+ 	.get_wol		= at803x_get_wol,
+ 	.suspend		= at803x_suspend,
+ 	.resume			= at803x_resume,
+-	/* PHY_GBIT_FEATURES */
++	.features               = PHY_GBIT_FEATURES,
+ 	.read_status		= at803x_read_status,
+ 	.aneg_done		= at803x_aneg_done,
+ 	.ack_interrupt		= &at803x_ack_interrupt,