Quoting Chuanhong Guo <gch981213@xxxxxxxxx>:
Hi Chuanhong,
The 2nd gmac of mediatek soc ethernet may not be connected to a PHY
and a phy-handle isn't always available.
Unfortunately, mt7530 dsa driver assumes that the 2nd gmac is always
connected to switch port 5 and setup mt7530 according to phy address
of 2nd gmac node, causing null pointer dereferencing when phy-handle
isn't defined in dts.
MT7530 tries to detect if 2nd GMAC is using a phy with phy-address 0 or 4.
If so, switch port 5 needs to be setup so that PHY 0 or 4 is available
via port 5 of the switch. Any MAC can talk to PHY 0/4 directly via port 5.
This is also explained in the kernel docs mt7530.txt.
May be there are better way to detect that any node is using phy 0/4 of
the switch.
Funny that I never tested this case that 2nd gmac node exits and is disabled
without using port 5.
Thanks for the fix.
Tested-by: René van Dorst <opensource@xxxxxxxxxx>
Greats,
René
This commit fix this setup code by checking return value of
of_parse_phandle before using it.
Fixes: 38f790a80560 ("net: dsa: mt7530: Add support for port 5")
Signed-off-by: Chuanhong Guo <gch981213@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
mt7530 is available as a standalone chip and we should not make it
tightly coupled with a specific type of ethernet dt binding in the
first place.
A proper fix is to replace this port detection logic with a dt
property under mt7530 node, but that's too much for linux-stable.
drivers/net/dsa/mt7530.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 6e91fe2f4b9a..1d53a4ebcd5a 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -1414,6 +1414,9 @@ mt7530_setup(struct dsa_switch *ds)
continue;
phy_node = of_parse_phandle(mac_np, "phy-handle", 0);
+ if (!phy_node)
+ continue;
+
if (phy_node->parent == priv->dev->of_node->parent) {
ret = of_get_phy_mode(mac_np, &interface);
if (ret && ret != -ENODEV)
--
2.25.1
