Ethernet phys normally need a 25MHz refclk input. On a lot of boards
this is done with a dedicated 25MHz crystal. But the rk3588 CRU also
provides a means for that via the refclko25m_ethX clock outputs that
can be used for that function.
The mdio bus normally probes devices on the bus at runtime, by reading
specific phy registers. This requires the phy to be running and thus
also being supplied by its reference clock.
While there exist the possibility and dt-binding to declare these
input clocks for each phy in the phy-dt-node, this is only relevant
_after_ the phy has been detected and during the drivers probe-run.
This results in a chicken-and-egg-problem. The refclks in the CRU are
running on boot of course, but phy-probing can very well happen after
clk_disable_unused has run.
In the past I tried to make clock-handling part of the mdio bus code [0]
but that wasn't very well received, due to it being specific to OF and
clocks with the consensus being that resources needed for detection
need to be enabled before.
So to make probing ethernet phys using the internal refclks possible,
make those 2 clocks critical.
[0] https://lore.kernel.org/netdev/13590315.F0gNSz5aLb@diego/T/
Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Link: https://lore.kernel.org/r/20241214224820.200665-1-heiko@sntech.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
cd8b536663