On Sun, 27 Oct 2019 at 03:34, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>
> On Thu, Oct 24, 2019 at 07:00:38PM +0200, Ulf Hansson wrote:
> > On Thu, 24 Oct 2019 at 18:33, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> > >
> > > On Thu, Oct 10, 2019 at 01:39:36PM +0200, Ulf Hansson wrote:
> > > > In case we have succeeded to attach a CPU to its PM domain, let's deploy
> > > > runtime PM support for the corresponding attached device, to allow the CPU
> > > > to be powered-managed accordingly.
> > > >
> > > > To set the triggering point for when runtime PM reference counting should
> > > > be done, let's store the index of deepest idle state for the CPU in the per
> > > > CPU struct. Then use this index to compare the selected idle state index
> > > > when entering idle, as to understand whether runtime PM reference counting
> > > > is needed or not.
> > > >
> > > > Note that, from the hierarchical point view, there may be good reasons to
> > > > do runtime PM reference counting even on shallower idle states, but at this
> > > > point this isn't supported, mainly due to limitations set by the generic PM
> > > > domain.
> > > >
> > > > Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > > > ---
> > > > drivers/cpuidle/cpuidle-psci.c | 21 +++++++++++++++++++--
> > > > 1 file changed, 19 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
> > > > index 1510422c7a53..0919b40c1a85 100644
> > > > --- a/drivers/cpuidle/cpuidle-psci.c
> > > > +++ b/drivers/cpuidle/cpuidle-psci.c
> > > > @@ -16,6 +16,7 @@
> > > > #include <linux/of.h>
> > > > #include <linux/of_device.h>
> > > > #include <linux/psci.h>
> > > > +#include <linux/pm_runtime.h>
> > > > #include <linux/slab.h>
> > > >
> > > > #include <asm/cpuidle.h>
> > > > @@ -25,6 +26,7 @@
> > > >
> > > > struct psci_cpuidle_data {
> > > > u32 *psci_states;
> > > > + u32 rpm_state_id;
> > > > struct device *dev;
> > > > };
> > > >
> > > > @@ -50,14 +52,28 @@ static int psci_enter_idle_state(struct cpuidle_device *dev,
> > > > struct cpuidle_driver *drv, int idx)
> > > > {
> > > > int ret;
> > > > - u32 *states = __this_cpu_read(psci_cpuidle_data.psci_states);
> > > > - u32 state = psci_get_domain_state();
> > > > + struct psci_cpuidle_data *data = this_cpu_ptr(&psci_cpuidle_data);
> > > > + u32 *states = data->psci_states;
> > > > + struct device *pd_dev = data->dev;
> > > > + bool runtime_pm = (pd_dev && data->rpm_state_id == idx);
> > > > + u32 state;
> > >
> > > Wonder if we can have separate psci_enter_idle_state for OSI mode so
> > > that all these runtime extra check can be reduced ? It will also make
> > > sure there's no additional latency for PC mode because of OSI.
> >
> > Good idea, that's the plan. See previous answer.
> >
> > Perhaps if I add a patch on top, implementing your suggestion, would
> > you be happy with that?
>
> No, I prefer to amend this itself to keep it easy to be able to bisect.
Alright!
So I explored this a little bit more - and it actually forced me to
re-order some of the patches in the series, but it seems to have
turned out well.
In the new approach I have taken, I haven't replaced the actual
callback for the idle state, but instead make an early decision in
psci_enter_idle_state(), based on one single read of a per CPU
variable/struct. This tell what path to go.
I am running some final test, but should be able to post a new version
tomorrow. Although, if you still don't think the new approach is good
enough, we can always invent a callback, that we can assign when the
CPU is attached to PM domain. In any case, you will have to tell what
you think, after I posted the new version, just wanted to give you a
heads up.
Kind regards
Uffe
