Re: [PATCH v1] PM: sleep: core: Synchronize runtime PM status of parents and children

Johan Hovold
2025-02-07T16:26:21Z

On Fri, Feb 07, 2025 at 05:06:32PM +0100, Johan Hovold wrote:
> On Fri, Feb 07, 2025 at 04:41:18PM +0100, Rafael J. Wysocki wrote:
> > On Fri, Feb 7, 2025 at 3:45 PM Johan Hovold <johan@kernel.org> wrote:
> > > On Fri, Feb 07, 2025 at 02:50:29PM +0100, Johan Hovold wrote:
>
> > > Ok, so the driver data is never set and runtime PM is never enabled for
> > > this simple bus device, which uses pm_runtime_force_suspend() for system
> > > sleep.
> >
> > This is kind of confusing. Why use pm_runtime_force_suspend() if
> > runtime PM is never enabled and cannot really work?
>
> It's only done for some buses that this driver handles. The driver is
> buggy; I'm preparing a fix for it regardless of the correctness of the
> commit that now triggered this.

Hmm. The driver implementation is highly odd, but actually works as long
as the runtime PM status is left at 'suspended' (as
pm_runtime_force_resume() won't enable runtime PM unless it was enabled
before suspend).

So we'd strictly only need something like the below if we are going to
keep the set_active propagation.

Johan

diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
index 5dea31769f9a..d8e029e7e53f 100644
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -109,9 +109,29 @@ static int simple_pm_bus_runtime_resume(struct device *dev)
return 0;
}

+static int simple_pm_bus_suspend(struct device *dev)
+{
+ struct simple_pm_bus *bus = dev_get_drvdata(dev);
+
+ if (!bus)
+ return 0;
+
+ return pm_runtime_force_suspend(dev);
+}
+
+static int simple_pm_bus_resume(struct device *dev)
+{
+ struct simple_pm_bus *bus = dev_get_drvdata(dev);
+
+ if (!bus)
+ return 0;
+
+ return pm_runtime_force_resume(dev);
+}
+
static const struct dev_pm_ops simple_pm_bus_pm_ops = {
RUNTIME_PM_OPS(simple_pm_bus_runtime_suspend, simple_pm_bus_runtime_resume, NULL)
- NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+ NOIRQ_SYSTEM_SLEEP_PM_OPS(simple_pm_bus_suspend, simple_pm_bus_resume)
};

#define ONLY_BUS ((void *) 1) /* Match if the device is only a bus. */