On Wed, May 18, 2011 at 09:43:13PM +0200, Rafael J. Wysocki wrote: > On Wednesday, May 18, 2011, mark gross wrote: > > On Wed, May 18, 2011 at 01:07:57AM +0200, Rafael J. Wysocki wrote: > > > On Saturday, May 14, 2011, mark gross wrote: > > > > On Fri, May 13, 2011 at 06:54:57PM +0200, Rafael J. Wysocki wrote: > > > > > On Friday, May 13, 2011, Raffaele Recalcati wrote: > > > > > > Hi Rafael, > > > > > > > > > > > > 2011/5/12 Rafael J. Wysocki <rjw@xxxxxxx>: > > > > > > > On Thursday, May 12, 2011, Raffaele Recalcati wrote: > > > > > > >> What happen normally in runtime pm implementation is that every devices > > > > > > >> are switched off and are enabled only when needed. > > > > > > >> In our case instead we have a completely functional embedded system and, > > > > > > >> when an asyncrhonous event appear, we have only some tens milliseconds > > > > > > >> before the actual power failure takes place. > > > > > > >> This patchset add a support in order to switch off not vital part of the system, > > > > > > >> in order to allow the board to survive longer. > > > > > > >> This allow the possibility to save important data. > > > > > > > > > > > > > > OK, so first, who decides what parts of the system are vital and what aren't? > > > > > > > > > > > > Take a quick look at Documentation/power/loss.txt paragrpah "2.4 > > > > > > Power loss policies". > > > > > > You can decide what can be powered off. > > > > > > > > > > I read the patches. My question was about the general idea of who should > > > > > be responsible of making these decisions. > > > > > > > > I would expect the system integrator would based on the application the > > > > device is getting deployed into. > > > > > > > > A generic opportunistic policy for peripherals that are stateless and can > > > > be trivially power gated off/on from an ISR could be a default but, for > > > > peripherals that need to do some processing (like waiting on an eMMC DMA > > > > to complete) can take time to power down into a safe state. > > > > > > What do you mean by safe state? > > > > > I need to get more details on this but I assume its a state where the > > meta data of the file system is committed to the emmc before lights go > > off such that when power is reapplied that the damage isn't too big. > > I don't think you can guarantee that the metadata won't be damaged > without notifying the filesystem of the event (and making it react > appropriately). > true. I'm just brain storming what infrastructure would be needed to support such a feature. > > I've also heard some talk of sim card corruption risks but, I don't have > > first hand info on that. > > Well, I guess that might be prevented by the driver alone. Only the radio has a direct interface to the sim. (pretty sure anyway) so this would transfer into some AT commands pushed to the modem. --mark _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
