On Thu, Sep 03, 2020 at 03:28:22PM -0600, Rob Herring wrote: > What if a device requires clocks enabled in a certain order or timing? > It's not just clocks, you could have some GPIOs or a regulator that > need enabling first. It's device specific, so really needs a per > device solution. This is not just an issue with MDIO. I think we > really need some sort of pre-probe hook in the driver model in order > to do any non-discoverable init for discoverable buses. Hi Rob How do you solve the chicken/egg of knowing what device specific init is needed before you can discover what device you have on the bus? > Or perhaps forcing probe when there are devices defined in DT if > they're not discovered by normal means. The PHY subsystem has this. You came specify in DT the ID of the device which we would normally read during bus discovery. The correct driver is then loaded and probed. But it is good practice to avoid this. OEMs are known to change the PHY in order to perform cost optimisation. So we prefer to do discover and do the right thing if the PHY has changed. As for GPIOS and regulators, i expect this code will expand pretty soon after being merged to handle those. There are users wanting it. We already have some standard properties defined, in terms of gpios, delay while off, delay after turning it on. As for ordering, i guess it would make sense to enable the clocks and then hit it with a reset? If there is a device which cannot be handled like this, it can always hard code its ID in device tree, and fully control its resources in the driver. Andrew
