Hi, > -----Original Message----- > From: Sakari Ailus [mailto:sakari.ailus@xxxxxxxxx] > Sent: 28. huhtikuuta 2011 12:34 > To: Jokiniemi Kalle (Nokia-SD/Tampere) > Cc: broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx; lrg@xxxxxxxxxxxxxxx; > mchehab@xxxxxxxxxxxxx; svarbatov@xxxxxxxxxx; saaguirre@xxxxxx; > grosikopulos@xxxxxxxxxx; Zutshi Vimarsh (Nokia-SD/Helsinki); linux- > kernel@xxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx; Laurent Pinchart > Subject: Re: [RFC] Regulator state after regulator_get > > Hello, > > Jokiniemi Kalle (Nokia-SD/Tampere) wrote: > > Hello regulator FW and OMAP3 ISP fellows, > > > > I'm currently optimizing power management for Nokia N900 MeeGo DE > release, > > and found an issue with how regulators are handled at boot. > > > > The N900 uses VAUX2 regulator in OMAP3430 to power the CSIb IO complex > > that is used by the camera. While implementing regulator FW support to > > handle this regulator in the camera driver I noticed a problem with the > > regulator init sequence: > > > > If the device driver using the regulator does not enable and disable the > > regulator after regulator_get, the regulator is left in the state that it was > > after bootloader. In case of N900 this is a problem as the regulator is left > > on to leak current. Of course there is the option to let regulator FW disable > > all unused regulators, but this will break the N900 functionality, as the > > regulator handling is not in place for many drivers. > > > > I found couple of solutions to this: > > 1. reset all regulators that have users (regulator_get is called on them) with > > a regulator_enable/disable cycle within the regulator FW. > > 2. enable/disable the specific vdds_csib regulator in the omap3isp driver > > to reset this one specific regulator to disabled state. > > > > So, please share comments on which approach is more appropriate to take? > > Or maybe there is option 3? > > > > Here are example code for the two options (based on .37 kernel, will update > > on top of appropriate tree once right solution is agreed): > > > > Option1: > > > > If a consumer device of a regulator gets a regulator, but > > does not enable/disable it during probe, the regulator may > > be left active from boot, even though it is not needed. If > > it were needed it would be enabled by the consumer device. > > > > So reset the regulator on first regulator_get call to make > > sure that any regulator that has users is not left active > > needlessly. > > I'm not an expert in the regulator framework, but I'd think that one > should be able to assume a regulator is in a sane state after boot. The > fact that the regulator is enabled when it has no users should likely be > fixed in the boot loader. Is that an option? Not an option, the device has shipped and there will be no updates to the bootloader. > > Does the problem exist in other boards beyond N900? Don't know, I currently have only N900 to test with. > > Another alternative to the first option you proposed could be to add a > flags field to regulator_consumer_supply, and use a flag to recognise > regulators which need to be disabled during initialisation. The flag > could be set by using a new macro e.g. REGULATOR_SUPPLY_NASTY() when > defining the regulator. This sounds like a good option actually. Liam, Mark, any opinions? - Kalle > > Just my 0,05 euros. ;-) > > Cc Laurent Pinchart. > > Regards, > > -- > Sakari Ailus > sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
