On Thu, 19 Oct 2023 at 19:08, Stephan Gerhold stephan@gerhold.net wrote:
On Thu, Oct 19, 2023 at 05:19:53PM +0200, Ulf Hansson wrote:
On Thu, 19 Oct 2023 at 16:49, Stephan Gerhold stephan@gerhold.net wrote:
On Thu, Oct 19, 2023 at 04:12:56PM +0200, Ulf Hansson wrote:
On Thu, 19 Oct 2023 at 15:05, Stephan Gerhold stephan@gerhold.net wrote:
On Thu, Oct 19, 2023 at 01:26:19PM +0200, Ulf Hansson wrote:
BTW, if you really need something like the above, the proper way to do it would instead be to call device_set_awake_path() for the device.
This informs genpd that the device needs to stay powered-on during system suspend (assuming that GENPD_FLAG_ACTIVE_WAKEUP has been set for it), hence it will keep the corresponding PM domain powered-on too.
Thanks, I can try if this works as alternative to the dev_pm_syscore_device()!
Yes, please. We don't want to abuse the dev_pm_syscore_device() thingy.
Could you clarify the idea behind GENPD_FLAG_ACTIVE_WAKEUP? Would I set it conditionally for all RPMPDs or just the ones consumed by the CPU? How does the genpd *provider* know if one of its *consumer* devices needs to have its power domain kept on for wakeup?
We are thinking of the GENPD_FLAG_ACTIVE_WAKEUP as a platform configuration type of flag for the genpd in question. The consumer driver shouldn't need to know about the details of what is happening on the PM domain level - only whether it needs its device to remain powered-on during system suspend or not.
Thanks! I will test if this works for RPMPD and post new versions of the patches. By coincidence I think this flag might actually be useful as temporary solution for CPR. If I:
- Change $subject patch to use device_set_awake_path() instead, and
- Set GENPD_FLAG_ACTIVE_WAKEUP for the RPMPD genpds, but
- Do *not* set GENPD_FLAG_ACTIVE_WAKEUP for the CPR genpd.
Then the genpd ->power_on|off() callbacks should still be called for CPR during system suspend, right? :D
Yes, correct, that should work fine!
I suspect that the GENPD_FLAG_ACTIVE_WAKEUP is probably okay to set for most genpds, but there may be some exceptions.
Out of curiosity, do you have an example for such an exception where GENPD_FLAG_ACTIVE_WAKEUP shouldn't be set, aside from workarounds like I just described?
As you said, the consumer device should just say that it wants to stay powered for wakeup during suspend. But if its power domains get powered off, I would expect that to break. How could a genpd driver still provide power without being powered on? Wouldn't that rather be a low performance state?
I think this boils down to how the power-rail that the genpd manages, is handled by the platform during system suspend.
In principle there could be some other separate logic that helps a FW/PMIC to understand whether it needs to keep the power-rail on or not - no matter whether the genpd releases its vote for it during system suspend.
This becomes mostly hypothetical, but clearly there are a lot of genpd/platforms that don't use GENPD_FLAG_ACTIVE_WAKEUP too. If those are just mistakes or just not needed, I don't actually know.
Kind regards Uffe