+ Mark, Liam for regulator questions, thread in archives here: http://marc.info/?l=linux-omap&m=128349777617270&w=2 "Gopinath, Thara" <thara@xxxxxx> writes: >>>-----Original Message----- >>>From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] >>>Sent: Thursday, September 02, 2010 4:22 AM >>>To: Gopinath, Thara >>>Cc: linux-omap@xxxxxxxxxxxxxxx; paul@xxxxxxxxx; Sripathy, Vishwanath; Sawant, Anand; Cousson, Benoit; >>>thomas.petazzoni@xxxxxxxxxxxxxxxxxx >>>Subject: Re: [PATCH 01/13] OMAP: Introduce a user list for each voltage domain instance in the >>>voltage driver. >>> >>>Thara Gopinath <thara@xxxxxx> writes: >>> >>>> This patch introduces a user list of devices associated with each >>>> voltage domain instance. The user list is implemented using plist >>>> structure with priority node populated with the voltage values. >>>> This patch also adds an API which will take in a device and >>>> requested voltage as parameters, adds the info to the user list >>>> and returns back the maximum voltage requested by all the user >>>> devices. This can be used anytime to get the voltage that the >>>> voltage domain instance can be transitioned into. >>>> >>>> Signed-off-by: Thara Gopinath <thara@xxxxxx> >>> >>>Looking closer at this, keeping track of a list of devices and >>>constraints is what the regulator framework does as well. >>> >>>Before we get too far down this path, we need to start working with >>>Thomas Petazzoni to better understand how we can use the regulator >>>framework for much of the management levels of the voltage layer. >>> >>>I'd rather not re-invent some of the management/constraints management >>>that could be done by the regulator framework. >>> >>>Basically, I think >>> >>> r = regulator_get(dev, voltdm->name) >>> regulator_set_voltage(r, volt) >>> >>>would basially be the equivalent of >>> >>> omap_voltage_add_userreq(voldm, dev, &volt); >>> omap_scale_voltage(voltdm, volt) > > Hello Kevin, > > Let me startr off by saying that I am not an expert on regulator > framework and hence my assessment below could be wrong. > I agree probably regulator framework would be > the best place for this but then IMO regulator framework needs a lot of > changes to support the kind of use-counting we need in the voltage layer. > To start with regulator_get keeps the use counting only for enabling or > disabling a regulator. It does not have a mechanism of adding the requested > voltage to a list and picking out the highest among the added values. Like you, I'm no expert on the regulator framework internals, but it appears to have a pretty thorough system of constraints management that upon first glance seems to be a good fit for what we need. It may need to be extended, but I would rather see us enhance the regulator framework than re-invent the constraints management. > regulator_set_voltage could be used to route the call to omap_scale_voltage > but then it is just a wrapper. Yes, just a wrapper, but users would be then using a a well defined and well documented API. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
