On Wed, Jun 11, 2014 at 3:43 PM, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote: > On Wed, Jun 11, 2014 at 05:52:10AM +0100, Chander Kashyap wrote: >> Hi Doug, >> >> On Tue, Jun 10, 2014 at 9:19 PM, Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> wrote: >> > On Tue, 10 Jun 2014, Doug Anderson wrote: >> > >> >> My S-state knowledge is not strong, but I believe that Lorenzo's >> >> questions matter if we're using S2 for CPUidle (where we actually turn >> >> off power and hot unplug CPUs) but not when we're using S1 for CPUidle >> >> (where we just enter WFI/WFE). >> >> >> >> No Its not plain WFI. >> >> All cores in Exynos5420 can be powered off independently. >> This functionality has been tested. >> >> Below is the link for the posted patches. >> >> https://lkml.org/lkml/2014/6/10/194 >> >> And as Nicolas wrote, these patches need MCPM for that. > > Chander, I cast a look into the code and I have a question > (you also told me on CPUidle review that only core off > is supported in CPUidle). > > When you say all cores can be powered off independently, do > you also mean that clusters can be powered off (in CPUidle) ? > > I am pointing this out since in the MCPM backend I noticed: > > "/* TODO: Turn off the cluster here to save power. */" > > I do not see any cluster power down request in the down path. > > If I am wrong, ignore my message, I am just writing to help. > > If you can only power down cores, but not the clusters on idle, > please keep in mind that you are currently cleaning and invalidating > the L2 when last man is running and this must not be taken > lightly since, if L2 stays on, that's a massive energy waste > for nothing. > > So, if clusters stay up, you _have_ to tweak the MCPM backend slightly > to avoid cleaning L2, that's pivotal. Hi Lorenzo, Cluster shutdown is in progress. Abhilash will add support for that. https://www.mail-archive.com/linux-samsung-soc@xxxxxxxxxxxxxxx/msg31104.html > > Lorenzo > >> >> >> I believe that in ChromeOS we use S1 CPUidle and that it works fine. >> >> We've never implemented S2 that I'm aware of. >> > >> > You'll have to rely on MCPM for that. That's probably why it hasn't >> > been implemented before. >> > >> > >> > Nicolas >> > >> > _______________________________________________ >> > linux-arm-kernel mailing list >> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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