Re: [PATCH net-next 1/3] net: phy: Support enabling clocks prior to bus probe

[Andrew Lunn <andrew@lunn.ch>]

On Wed, Sep 02, 2020 at 09:39:45PM -0700, Florian Fainelli wrote:
> Some Ethernet PHYs may require that their clock, which typically drives
> their logic to respond to reads on the MDIO bus be enabled before
> issusing a MDIO bus scan.

issuing

> 
> We have a chicken and egg problem though which is that we cannot enable
> a given Ethernet PHY's device clock until we have a phy_device instance
> create and called the driver's probe function. This will not happen
> unless we are successful in probing the PHY device, which requires its
> clock(s) to be turned on.
> 
> For DT based systems we can solve this by using of_clk_get() which
> operates on a device_node reference, and make sure that all clocks
> associaed with the node are enabled prior to doing any reads towards the

associated.

> device. In order to avoid drivers having to know the a priori reference
> count of the resources, we drop them back to 0 right before calling
> ->probe() which is then supposed to manage the resources normally.

  Andrew