On 23/02/17 15:26, Geert Uytterhoeven wrote: > Hi Sudeep, > > On Wed, Feb 22, 2017 at 3:32 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote: >> On 22/02/17 13:38, Geert Uytterhoeven wrote: >>> On Wed, Feb 22, 2017 at 12:03 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote: >>>> On 22/02/17 01:14, Rafael J. Wysocki wrote: >>>>> On Tuesday, February 21, 2017 06:45:13 PM Sudeep Holla wrote: >>>> Geert, so far you have failed to explain what's different from the new >>>> state you are adding and the existing s2idle. >>> >>> I did explain, cfr.: >>> 1. The power consumption figures in the cover letter: >>> - shallow: 8.4 W 6.2 W (secondary CPU cores off) >> >> That's because your CPU_SUSPEND implementation is incomplete. You can >> enter the same state as secondary CPU core off even with idle. It's just >> that we can save by not entering and exiting the CPU hotplug state >> machine. So this "shallow" state can be achieved if your CPU_SUSPEND >> implements that state. > > Does that include power areas? > OK, I first I didn't understand what you are referring here but I see some reference further in the email. >>> 2. The description for patch 3/6: >>> As secondary CPU cores are taken offline, "shallow" suspend mode saves >>> slightly more power than "s2idle", but less than "deep" suspend mode. >>> However, unlike "deep" suspend mode, "shallow" suspend mode can be used >>> regardless of the presence of support for PSCI_SYSTEM_SUSPEND, which is >>> an optional API in PSCI v1.0. >> >> Yes I understood that, you need to add an extra idle states to get that >> shallow state. We have discussed this in past to depth. On ARM64/PSCI, >> we will that support "shallow" system suspend mode which can't be >> defined generically. Also we can support this shallow state with s2idle. >> >> Your system probably not supporting all the CPU idle states. E.g.: it >> may just support CPU ON/OFF/RET and not cluster ON/OFF/RET. Please add >> that state to CPU_SUSPEND implementation in the firmware. > > I can find CPU_ON and CPU_OFF in the PSCI specification, but not > CPU_RET? > No, they were just examples of idle states that CPU_SUSPEND call might support based on what h/w can support on a particular platform. > How is the cluster ON/OFF/RET called exactly? I can't find any CLUSTER_* > calls in the PSCI specification. > CPU_SUSPEND with different parameters, just look at the details on suspend parameters in Section 5.4.2 CPU_SUSPEND parameters: power_state > From a quick glance in the PSCI sources, there's some support for powering > down clusters. > Yes, the above section should provide some insight on the same. >>> Perhaps, I didn't make myself clear. Let's summarize: >>> 1. On Renesas R-Car Gen3 platforms, PSCI SYSTEM_SUSPEND is implemented, >> >> OK got that. >> >>> 2. On these platforms, PSCI SYSTEM_SUSPEND powers down the SoC, and supports >>> wake-up from PMIC only, >> >> OK >> >>> 3. If the user wants to use a different wake-up source, these other >>> wake-up sources fail to wake up the system from PSCI SYSTEM_SUSPEND. >> >> In that case don't enter PSCI SYSTEM_SUSPEND > > Or prevent the system from doing that... > Agreed. >>> 4. Patch 3/6 adds a new "shallow" state, as it allows to save more >>> power (the difference may be due to suboptimal cpuidle platform support on R-Car Gen3, though), >> >> Why can't you do that in s2idle mode. Please give me the difference >> between your shallow state and s2idle state, not just power numbers >> but the actual state of CPUs and the devices in the system. > > From the Linux side, there's not much difference, except that the secondary > CPU cores are disabled. As that is handled by PSCI, the difference may be > in the PSCI implementation. I will have to check that... > Yes it's better to check. I am afraid that both these states will be same if PSCI implementation is correct and hence we don't want to support standby suspend mode. > On these SoCs, the individual CPU cores and the SCU/L2 are in separate > (nested) power areas. Perhaps these power areas are turned off when > disabling the CPU cores, but not when suspending them. > Yes that's what I suspect and hence I said it's incomplete implementation of CPU_SUSPEND >>> E.g. on non-PSCI platforms with an Ethernet driver that supports >>> Wake-on-LAN, I can do: >>> >>> ethtool -s eth0 wol g >>> echo mem > /sys/power/state >>> >>> and be sure that the system can be woken up by sending a WoL MagicPacket. >> >> Still possible with s2idle if CPU_SUSPEND is correctly implemented by >> the platform. > > Sure. But not automatic, as it needs fiddling with mem_sleep. > Yes that's true form any thing other than "deep" state. i.e. s2idle or standby. If you are OK to choose standby why not s2idle ? >>> On PSCI systems, the above may work, or may not work. And there's no way to >>> find out (in an automated way) whether it will work or not. >>> >>> If it doesn't work, the user has to configure his system (manually) to >>> not use "mem" state. >>> Since v4.10-rc1, that can be done using e.g. >>> >>> echo s2idle > /sys/power/mem_sleep >>> >>> and my patches make that automatic (for a new "shallow" state instead >>> of "s2idle", though). >> >> How is that ? If "deep" is available as in your case too, why will >> shallow become default. IIUC the user still have to write "shallow" >> to mem_sleep. > > After patch 4, if needed (DT property + extra wake-up sources configured), > psci_system_suspend_enter() will call cpu_do_idle() instead of > psci_system_suspend(). No need to fiddle with mem_sleep manually. > I understand your intentions and but I have NACKed it with sufficient reasoning. I don't want to repeat them again here. >> Does this platform use generic arm64 DT cpuidle driver ? I don't see so >> from the DT. > > I think that task isn't complete yet. > So, all these hacks are just to cope up with that ? Sorry that's non-sense. Working around a firmware bug is different from working around the incomplete firmware implementation. We may consider former but for me latter is just insane. -- Regards, Sudeep
