Hi Andrew,
On Sat, Jan 20, 2024 at 08:21:25PM +0100, Andrew Lunn wrote:
When there is no device on the bus for a given address, the pull up resistor on the data line results in the read returning 0xffff. The phylib core code understands this when scanning for devices on the bus, and a number of MDIO bus masters make use of this as a way to indicate they cannot perform the read.
Make us of this as a minimal fix for stable where the mv88e6xxx
s/us/use/
Also, what is the "proper" fix if this is the minimal one for stable?
returns EOPNOTSUPP when the hardware does not support C45, but phylib interprets this as a fatal error, which it should not be.
I think the commit message is a bit backwards, it starts with an explanation of the solution without ever clarifying exactly what is the problem.
At least it could have referenced the old thread which explains that: https://lore.kernel.org/netdev/CAO-L_44YVi0HDk4gC9QijMZrYNGoKtfH7qsXOwtDwM4V...
Cc: stable@vger.kernel.org Reported-by: Tim Menninger tmenninger@purestorage.com Fixes: 1a136ca2e089 ("net: mdio: scan bus based on bus capabilities for C22 and C45") Fixes: da099a7fb13d ("net: phy: Remove probe_capabilities") Signed-off-by: Andrew Lunn andrew@lunn.ch
drivers/net/dsa/mv88e6xxx/chip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c index 383b3c4d6f59..614cabb5c1b0 100644 --- a/drivers/net/dsa/mv88e6xxx/chip.c +++ b/drivers/net/dsa/mv88e6xxx/chip.c @@ -3659,7 +3659,7 @@ static int mv88e6xxx_mdio_read_c45(struct mii_bus *bus, int phy, int devad, int err; if (!chip->info->ops->phy_read_c45)
return -EOPNOTSUPP;
return 0xffff;mv88e6xxx_reg_lock(chip); err = chip->info->ops->phy_read_c45(chip, bus, phy, devad, reg, &val); -- 2.43.0
Is this an RFC pending testing from Tim? Or have you reproduced the problem and confirmed that this fixes it? It's not clear how the old thread ended.