On 9/2/2020 2:33 PM, 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. 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 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.
That last part is actually not in this patch series, I had it in an intermediate version, but after chasing a clock enabling/disabling race that appears specific to the platforms I am using, I eventually removed it but left that part in the commit message.
-- Florian
