On Wed, Jan 25, 2017 at 05:15:52PM -0700, Al Stone wrote: > On 01/25/2017 04:27 PM, Dmitry Torokhov wrote: > > On Wed, Jan 25, 2017 at 02:44:10PM -0700, Al Stone wrote: > >> > >> But, to the point of some of the other discussion on the thread, this ACPI sort > >> of power management is a very, very different model than DT so that intertwining > >> the two models is highly unlikely to work, IMHO. > > > > And yet this is something that is sorely needed. If you look, for > > example, at drivers in drivers/input/*, then all non-SOC-specific > > devices can easily find their way onto both ACPI-based and DT-based > > systems (not mentioning legacy-style boards). Having two distinct power > > schemes implemented in drivers will lead to many problems. > > I really can't speak to those sorts of systems; where I deal with ACPI > is on enterprise-class server systems which seldom have a graphics card, > much less input devices other than a keyboard. Yeah, so basically no power management except for CPU states ;) > And in general, those > systems are required to use only ACPI. If a vendor wants their device to > work on such a system, they need to provide a driver that works with ACPI. > It may also work with DT, but in this environment it doesn't matter. > > Whether or not there are two power schemes is a moot point. We have DT > and we have ACPI, and they have very different schemes for power management, > so we're already there. And so far, my experience has been that as long as > the ACPI and DT parts of the driver are kept disjoint when the models diverge, > and share code when they are semantically absolutely identical, things work > pretty well. As someone who's actually shipping both ACPI and DT-based devices reusing the same peripherals I can assure you that it is really PITA to have different PM behavior in a single driver and if we can converge on something sane that would be great. > > > Having unified way of describing hardware is how _DSD came about, right? > > Nobody wanted to write and maintain and test two separate ways of > > describing properties when one was already implemented and working. > > I can't speak for those that proposed _DSD to be part of the ACPI spec, > but no, it was not meant as a unified way of describing hardware, as far > as I can remember from the ASWG discussions I was part of. The intent, > as I recall it, was to provide some of the same flexibility to ASL that > was available in DT. At the time, power managment was even discussed as > one of the areas where the DT model and the ACPI model clashed. That's not what I remember from discussions at Plumbers/KS... Binding compatibility, even if for simplest properties, was one of the points. Thanks. -- Dmitry -- 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
