On Monday, September 02, 2013 04:24:23 PM Daniel Lezcano wrote: > On 09/02/2013 03:48 PM, Bartlomiej Zolnierkiewicz wrote: > > On Monday, September 02, 2013 03:18:51 PM Daniel Lezcano wrote: > >> On 09/02/2013 11:41 AM, Bartlomiej Zolnierkiewicz wrote: > >>> On Monday, September 02, 2013 10:54:17 AM Daniel Lezcano wrote: > >>>> On 08/30/2013 12:21 PM, Bartlomiej Zolnierkiewicz wrote: > >>>>> Add "cpuidle-exynos.max_states=" parameter to allow user to specify > >>>>> the maximum of allowed CPU idle states for ARM EXYNOS cpuidle driver. > >>>>> > >>>>> This change is needed because C1 state (AFTR mode) is often not able > >>>>> to work properly due to incompatibility with some bootloader versions. > >>>>> > >>>>> Usage examples: > >>>>> > >>>>> "cpuidle-exynos.max_states=1" disables C1 state (AFTR mode). > >>>>> > >>>>> "cpuidle-exynos.max_states=0" disables the driver completely. > >>>>> > >>>>> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> > >>>>> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > >>>>> Cc: Tomasz Figa <t.figa@xxxxxxxxxxx> > >>>>> Cc: Amit Daniel Kachhap <amit.daniel@xxxxxxxxxxx> > >>>> > >>>> There is a max_cstate option for acpi and intel idle. There is also the > >>>> cpuidle.off=1 option. As the semantic is the same, I think adding a > >>>> common cpuidle option usable for all the drivers is better. > >>> > >>> I thought about making the option common for all cpuidle drivers first > >>> but due to support for multiple cpuidle drivers on one machine (i.e. > >>> big.LITTLE), per-driver option looked like a better approach. > >>> > >>> Should I make the option common and not worry about multiple drivers on > >>> one machine support? > >> > >> Mmh, that's a good point. > >> > >> I am not in favor of multiple options spread across the different > >> drivers. Furthermore the max_cstate is used in the intel platform to > >> 'discover' what states the firmware supports which is not the case of > >> the cpuidle ARM drivers (except new PSCI based). This option does not > >> really fits well here. > >> > >> There is the kernel parameter 'cpuidle.off', so disabling the driver is ok. > >> > >> You converted the cpuidle driver to a platform driver. Isn't possible to > >> pass information in the platform data field at boot time to tell AFTR is > >> not supported and then act on the 'disabled' field of this state ? > > > > It might be possible but I don't know where the source of this data would > > be, platform specific kernel parameter? It sounds just like moving the code > > around and adding superfluous platform->driver code because the similar > > kernel parameter to disable just AFTR can be added in cpuidle-exynos driver > > as well. > > It is to prevent to add a new kernel parameter (with the documentation) > for a single driver which has a bogus idle state. If that could be > handled internally that would be cleaner. If I believed that it could be handled internally I wouldn't be trying to add a kernel parameter to handle it.. Would I? ;) > Can you shortly describe what happens with the bootloader and AFTR ? AFTR just doesn't work with the custom U-Boot version that we are using (attempts to go into AFTR mode result in lockup) and using the upstream version of U-Boot is not an option since it doesn't support the hardware that we are using AFAIK. I also don't know exactly why it doesn't work (I just suspect that it reuses INFORM registers for some other purposes). > I guess you are not interested in cpuidle.off=1 because you want cpuidle > statistics for WFI, right ? Right. :) Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics -- 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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