Messages in this thread | | | Date | Tue, 1 Sep 2009 11:23:24 +0100 | From | Mark Brown <> | Subject | Re: [PATCH 1/2] AB3100 regulator support v2 |
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On Mon, Aug 31, 2009 at 04:16:15PM +0200, Linus Walleij wrote: > 2009/8/31 Mark Brown <broonie@opensource.wolfsonmicro.com>:
> >> + err = ab3100_get_register_interruptible(abreg->ab3100, abreg->regreg, > >> + ®val);
> > I did query last time if having these operations be interruptible is a > > good idea - I can't see it helping robustness, it's not something that > > other drivers are doing and it'd complicate things for all API users to > > add handling for the error. I don't recall any discussion of the > > thinking here?
> I recently renamed all the ab3100 accessor functions to *_interruptible > to reflect the fact that the accessor mutex on ab3100 uses > mutex_lock_interruptible() so this suffix should propagate so it is > clear that stuff like -ERESTARTSYS can be returned. > So the above errorcheck is probably bogus.
Oh, there's no noninterruptible version? With the naming it looked like there was.
> That said, I think the regulator paths are entirely in-kernel and > under such circumstances that signals from userspace are blocked > anyway. The problem is that the ab3100 is accessed by complex
The regulator API doesn't give any guarantees that signals can't be delivered.
> userspace programs and I2C is sometimes slow so there is a need > for being able to interrupt it, but I *could* go in and use an
While I2C isn't fast for the sorts of access regulators tend to do it's not so slow as to make this critical.
> uniterruptable mutex if you prefer that, I'll ask around here if > we should do this. Can the function name stand as it is for the time being?
> >> +static int ab3100_get_voltage_regulator_external(struct regulator_dev *reg) > >> +{
> > Hrm. I suspect that you either want to add some platform data to > > specify the voltage as a plain number or just have boards use the > > regulator supply mechanism with a fixed voltage regulator supplied by > > this one if they need to specify the voltage of the supply.
> I was designing for it to be controllable but not controllable by the > AB3100 driver, perhaps it is a regulator somewhere else here, > defined in the board data. But I went for a fixed int member > voltage setting for the time being, we can discuss that stuff later > when I have some practical use for it.
I've got the same sort of external switch on the WM831x. What I did there was just not have the voltage at all. The regulator API supports chaining of regulators so one regulator is the supply for another so what a board could do is set things up so that the switch on the PMIC is the supply for an external regulator. There's already a standard driver for simple fixed voltage regulators and if the regulator is more complex and supports variable voltages then it can use its normal driver.
> If this sequence is a dependency graph of regulators that need to > have deps in all strange directions you get a directed graph > http://en.wikipedia.org/wiki/Directed_graph > Or you could limit yourself to a directed acyclic graph > http://en.wikipedia.org/wiki/Directed_acyclic_graph > in either case it's rather a delicate computational problem > but I guess you're after a simple linear sequence here, like > switch on A, B, C, D ... N in a special order?
The power sequencing provided by hardware designers is normally a simple linear sequence of things to do to bring the system power up - normally you'd bring some supplies up, wait for a given time period then bring some more up and so on. Sometimes there will be some handshaking involved (waiting for "I've started" signals from components).
> In my case it's actually not the switching-on or of that is > the problem, it's more of putting some magic numbers > into some registers in a special order (well, any order > actually except for one register that is special).
> I'll see if I can think of something more elegant to > make this more appealing, like tagging each default > register value with a sequence number or so.
Are the magic numbers controlling things other than the settings that are exposed through the regulator API? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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