On 22/11/2022 10:01, Geert Uytterhoeven wrote: >>>>> The h2mode bit (and probably a few other controls we haven't figured out >>>>> yet) in the sysctrl must be set before any of the USB devices is active. >>>>> Hence it's safest for the sysctrl to do this before any of the USB drivers >>>>> probes. >>>> >>>> Again, this does not differ from many, many of other devices. All of >>>> them must set something in system controller block, before they start >>>> operating (or at specific time). It's exactly the same everywhere. >>> >>> The issue here is that there are two _different drivers_ (USB host >>> and device). When both are modular, and the driver that depends on the >>> sysctrl setting is loaded second, you have a problem: the sysctrl change >>> must not be done when the first driver is already using the hardware. >>> >>> Hence the sysctrl driver should take care of it itself during early >>> initialization (it's the main clock controller, so it's a dependency >>> for all other I/O device drivers). >> >> I assumed you have there bit for the first device (which can switch >> between USB host and USB device) to choose appropriate mode. The >> bindings also expressed this - "the USBs are". Never said anything about >> dependency between these USBs. >> >> Are you saying that the mode for first device cannot be changed once the >> second device (which is only host) is started? IOW, the mode setup must >> happen before any of these devices are started? > > Exactly. > >> Anyway with sysctrl approach you will have dependency and you cannot >> rely on clock provider-consumer relationship to order that dependency. >> What if you make all clocks on and do not take any clocks in USB device? > > Enabling the clocks does not have anything to do with this ordering. That was the argument from Herve, that ordering is guaranteed by clocks. > Clock consumers that are part of the clock domain are probed after > clock providers. If the clock is missing, that would be an incorrect > description in DTS. If not clocks, what else is guaranteeing the ordering? You did not express it in DT. Best regards, Krzysztof
