On 一, 2月 20, 2017 at 10:47:56上午 +0000, Sudeep Holla wrote:
>
>
> On 20/02/17 09:37, Chunyan Zhang wrote:
> > Hi Sudeep,
> >
> > On 五, 2月 17, 2017 at 10:28:00上午 +0000, Sudeep Holla wrote:
> >>
> >>
> >> On 17/02/17 07:28, Chunyan Zhang wrote:
> >>> Hi Sudeep,
> >>>
> >>> On 二, 2月 14, 2017 at 04:44:53下午 +0000, Sudeep Holla wrote:
> >>>> On Tue, Feb 14, 2017 at 9:19 AM, Chunyan Zhang
> >>>> <chunyan.zhang@xxxxxxxxxxxxxx> wrote:
> >>
> >> [..]
> >>
> >>>>
> >>>>> + idle-states{
> >>>>> + entry-method = "arm,psci";
> >>>>> +
> >>>>> + CORE_PD: core_pd {
> >>>>> + compatible = "arm,idle-state";
> >>>>> + entry-latency-us = <1000>;
> >>>>> + exit-latency-us = <700>;
> >>>>> + min-residency-us = <2500>;
> >>>>> + local-timer-stop;
> >>>>> + arm,psci-suspend-param = <0x00010002>;
> >>>>> + };
> >>>>> +
> >>>>> + CLUSTER_PD: cluster_pd {
> >>>>> + compatible = "arm,idle-state";
> >>>>> + entry-latency-us = <1000>;
> >>>>> + exit-latency-us = <1000>;
> >>>>> + min-residency-us = <3000>;
> >>>>> + local-timer-stop;
> >>>>> + arm,psci-suspend-param = <0x01010003>;
> >>>>> + };
> >>>>> +
> >>>>> + DEEP_SLEEP: deep_sleep {
> >>>>> + compatible = "arm,idle-state";
> >>>>> + wakeup-latency-us = <0xffffffff>;
> >>>>
> >>>> A value > 4294 seconds(i.e >1 hour) seems suspicious.
> >>>> Are you working around the firmware issue with high latency value so
> >>>> that it's never entered ? Why not remove advertising the state from DT.
> >>>>
> >>>
> >>> Haved checked with related colleagues, this node 'deep_sleep' was not for working
> >>> around any firmware issue, but was a trick utilization of idle subsystem, and that
> >>
> >> Really ? Any latency greater few milliseconds are sounds useless. I
> >> still don't understand what you mean by "trick utilization of idle
> >> subsystem".
> >>
> >
> > Sorry for confused expression, I meant it was not a right way to utilize idle mechanism
> > and shouldn't be upstreamed.
> >
>
> No problem.
>
> >>> was definitely not elegant, the author indeed intendly didn't want CPU entered this
> >>> state, I will remove this node therefore.
> >>
> >> It's quick and dirty "HACK* to retain and advertise the state but
> >> ensure it's never entered and obstruct the boot. It's not a trick to
> >> exploit any idle subsystem utilization.
> >>
> >
>
> > Right, actually deep_sleep was for 'suspend' (forces idleness upon
> > the OS until a wake-up event resumes the OS from suspend), for
> > example when users press power key on mobile phone to turn off the
> > screen. So the author implemented 'suspend' using cpu_psci_ops::cpu_suspend
> > I figure that this way is not correct, I will remove this state from DT.
>
> OK.
>
> > I would appreciate any suggestion for how to implement this kind of
> > function properly.
>
>
> For the 'suspend' functionality you have described above, all you need
> is the firmware to implement PSCI SYSTEM_SUSPEND API in the firmware.
> The kernel psci driver detects the presence of the same and registers
> the suspend ops automatically. You need not add anything in the code or
> DT for the same.
Thank you Sudeep, I will have my colleague to study further according to
the direction you provided here.
Thanks for your comments,
Chunyan
>
> --
> Regards,
> Sudeep
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