On 6/29/2020 5:45 PM, Andrew Lunn wrote: > On Mon, Jun 29, 2020 at 10:26:36AM +0300, Claudiu Beznea wrote: >> In case of_mdiobus_register_phy()/of_mdiobus_register_device() >> returns -ENODEV for all PHYs in device tree or for all scanned >> PHYs there is a chance that of_mdiobus_register() to >> return success code although no PHY devices were registered. >> Add a counter that increments every time a PHY was registered >> to avoid the above scenario. > > Hi Claudiu > > There is a danger here this will break something. Without this patch, > an empty bus is O.K. But with this patch, a bus without a PHY is a > problem. > > Take for example FEC. It often comes in pairs. Each has an MDIO > bus. But to save pins, there are some designs which place two PHYs on > one bus, leaving the other empty. The driver unconditionally calls > of_mdiobus_register() and if it returns an error, it will error out > the probe. So i would not be too surprised if you get reports of > missing interfaces with this patch. Agreed, the potential for breakage here is too high especially given this is fixing a hypothetical problem rather an an actual one. Even if we were taking this from the angle of power management, runtime PM should ensure that a MDIO bus with no slave, or no activity gets runtime suspended. -- Florian
