> On 23. 8. 2022, at 13:51, Martin Povišer <povik+lin@xxxxxxxxxxx> wrote: > > > >> On 23. 8. 2022, at 13:31, Mark Brown <broonie@xxxxxxxxxx> wrote: >> >> On Tue, Aug 23, 2022 at 09:33:36AM +0200, Martin Povišer wrote: >>>> On 22. 8. 2022, at 19:39, Mark Brown <broonie@xxxxxxxxxx> wrote: >>>> On Fri, Aug 19, 2022 at 02:54:29PM +0200, Martin Povišer wrote: > >>>>> + /* >>>>> + * We can't power up the device earlier than this because >>>>> + * the power state driver would error out on seeing the device >>>>> + * as clock-gated. >>>>> + */ >>>>> + cl->pd_link = device_link_add(mca->dev, cl->pd_dev, >>>>> + DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME | >>>>> + DL_FLAG_RPM_ACTIVE); >> >>>> I'm not clear on this dynamically adding and removing device links stuff >>>> - it looks like the main (only?) purpose is to take a runtime PM >>>> reference to the target device which is fine but it's not clear why >>>> device links are involved given that the links are created and destroyed >>>> every time the DAI is used, AFAICT always in the same fixed >>>> relationship. It's not a problem, it's just unclear. >> >>> Indeed the only purpose is powering up the cluster’s power domain (there’s >>> one domain for each cluster). Adding the links is the only way I know to >>> do it. They need to be added dynamically (as opposed to statically linking, >>> say, the DAI’s ->dev to the cluster’s ->pd_dev, which I guess may do >>> something similar), because we need to sequence the power-up/power-down >>> with the enablement of the clocks. >> >> You could also just do the underlying runtime power management >> operations directly couldn't you? It's not clear what the device link >> stuff is adding. > > This seems to be the way to do it. Quoting from documentation of > dev_pm_domain_attach_by_id, by which we obtain the mca->dev and cl->pd_dev > the link is between: > > * This function should typically be invoked by a driver during the probe phase, > * in case its device requires power management through multiple PM domains. The > * driver may benefit from using the received device, to configure device-links > * towards its original device. Depending on the use-case and if needed, the > * links may be dynamically changed by the driver, which allows it to control > * the power to the PM domains independently from each other. > > -- > Martin Pardon, just the cl->pd_dev is from dev_pm_domain_attach_by_id, mca->dev is the original device. Martin
