On 08.01.2019 13:46, Rafael J. Wysocki wrote: > On Tue, Jan 8, 2019 at 11:56 AM <claudiu.bez...@microchip.com> wrote: >> >> From: Claudiu Beznea <claudiu.bez...@microchip.com> >> >> Hi, >> >> AT91 platforms support a power saving mode where SoC's power is cut off (we >> call >> it backup mode). The resume is done with the help of bootloaders. > > But still the contents of RAM are preserved?
Yes, the RAM is kept alive, in self-refresh (forgot to mention). Besides this, there is the so called backup area which contains RTC shutdown controller, RC oscillator which remains powered. The rest is off. > > That would require at least the memory controller to be under power AFAICS. Yes, this is powered by a different regulator. > >> To be able to >> suspend/resume Linux to/from this mode all the drivers suspend/resume >> callbacks >> should save/restore the content of all the active registers. We have 2 >> problems >> we are trying to solve: >> - some of these drivers are shared with other non Microchip SoCs (e.g. macb >> driver) and we don't want to disturbe other users of corresponding IPs with >> all the register save/restore operations; >> - the suspend/resume time for the rest of the power saving mode we are using >> could be improved if we would know in drivers the suspend mode the platform >> is switched to. >> >> A solution that would have been solve our problems was proposed in [1] but in >> the end it wasn't accepted. It ended up with the introduction of >> pm_suspend_target_state variable that could be used along with the changes in >> this series. >> >> While the discussion of [1] progressed it has been proposed (in [2]) to >> implement a function that would tell if the platform's power would be cut off >> at the end of the suspend procedure. >> >> The patches in this series does as follows: >> 1/3 - add a new member to platform_suspend_ops that will tell if platform's >> power will be cut off at the end of the suspend procedure; drivers >> could >> use it via platform_off_in_suspend() > > I would rather avoid doing this if possible. Having this mechanism as part of platform_suspend_ops? Or this mechanism at all? Could you give me some hints on how would you prefer to do it, if any? Thank you, Claudiu Beznea > > Thanks, > Rafael > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-ker...@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
