Hello, On Wed Nov 22, 2023 at 11:23 PM CET, Kevin Hilman wrote: > Théo Lebrun <theo.lebrun@xxxxxxxxxxx> writes: > > On Fri Nov 17, 2023 at 12:51 PM CET, Roger Quadros wrote: > >> On 17/11/2023 12:17, Théo Lebrun wrote: > >> > On Thu Nov 16, 2023 at 10:44 PM CET, Roger Quadros wrote: > >> >> On 16/11/2023 20:56, Théo Lebrun wrote: > >> >>> On Thu Nov 16, 2023 at 1:40 PM CET, Roger Quadros wrote: > >> >>>> On 15/11/2023 17:02, Théo Lebrun wrote: > >> >>>>> On Wed Nov 15, 2023 at 12:37 PM CET, Roger Quadros wrote: > >> >>>>>> You might want to check suspend/resume ops in cdns3-plat and > >> >>>>>> do something similar here. > >> >>>>> > >> >>>>> I'm unsure what you are referring to specifically in cdns3-plat? > >> >>>> > >> >>>> What I meant is, calling pm_runtime_get/put() from system suspend/resume > >> >>>> hooks doesn't seem right. > >> >>>> > >> >>>> How about using something like pm_runtime_forbid(dev) on devices which > >> >>>> loose USB context on runtime suspend e.g. J7200. > >> >>>> So at probe we can get rid of the pm_runtime_get_sync() call. > >> >>> > >> >>> What is the goal of enabling PM runtime to then block (ie forbid) it in > >> >>> its enabled state until system suspend? > >> >> > >> >> If USB controller retains context on runtime_suspend on some platforms > >> >> then we don't want to forbid PM runtime. > >> > > >> > What's the point of runtime PM if nothing is done based on it? This is > >> > the current behavior of the driver. > > The point is to signal to the power domain the device is in that it can > power on/off. These IP blocks are (re)used on many different SoCs, so > the driver should not make any assumptions about what power domain it is > in (if any.) On my platform, when the device is attached to the PD it gets turned on. That feels logical to me: if a driver is not RPM aware it "just works". Are there platforms where RPM must get enabled for the attached power-domains to be turned on? The call chain that attaches & enables PD is platform_probe -> dev_pm_domain_attach. That function takes a bool power_on which is always true. In the genpd case, genpd_dev_pm_attach calls __genpd_dev_pm_attach which does a genpd_power_on. Things I've not accounted for: - ACPI looks like it does the same but I've not checked. It gets passed the power_on bool argument. - genpd_dev_pm_attach early returns with no error if there are multiple PM domains attached to the device. There are many platforms in the case according to some devicetree grepping. I can imagine a behavior difference where dev_pm_domain callpaths handle that differently in the RPM case. Is that what we are discussing? > >> Even if driver doesn't have runtime_suspend/resume hooks, wouldn't > >> the USB Power domain turn off if we enable runtime PM and allow runtime > >> autosuspend and all children have runtime suspended? > > > > That cannot be the currently desired behavior as it would require a > > runtime_resume implementation that restores this wrapper to its desired > > state. > > Or, for this USB IP block to be in a power domain that has memory > retention, in which case the power domain can still go off to save > power, but not lose context. > > > It could however be something that could be implemented. It would be a > > matter of enabling PM runtime and that is it in the probe. No need to > > even init the hardware in the probe. Then the runtime_resume > > implementation would call the new cdns_ti_init_hw. > > This is the way. I agree & I have a prototype, but that requires some work on the child devices as from what I remember they are not eager to go to runtime suspend (ie a driver might be holding a reference). I feel this leans outside the scope of this patch series though. Regards, -- Théo Lebrun, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
