Quoting Nicolas Pitre (2013-07-18 10:47:22) > On Thu, 18 Jul 2013, Russell King - ARM Linux wrote: > > > 1. clk_get() and clk_put() are NOT part of the common clock API. > > They're separate - they're part of the clk API, and the infrastructure > > behind that is clkdev, which is a separately owned thing (by me.) > > > > 2. The "contract" of the clk API is defined by the clk API, not by some > > random implementation like the common clock API. The clk API is > > maintained by myself, and is described in include/linux/clk.h > > > > 3. clk_prepare() and clk_unprepare() are functions MUST only be called > > from contexts where sleeping is permitted. These functions MAY sleep > > for whatever reason they require to, and as long as they require to. > > (This is the whole reason these two functions were created in the > > first place.) > > > > 4. clk_enable() and clk_disable() MAY be called from any context, but > > MUST never sleep. If you need to talk over a non-atomic bus for these, > > then these functions should be no-ops, and the code which does that > > must be executed from the clk_prepare()/clk_unprepare() operations. > > Could the above be included in some form in Documentation/clk.txt (this > is likely one of the first location people look for information) and > elsewhere if appropriate please? > > A *lot* of people are confused by the prepare-enable-disable-unprepare > sequence and when I try to find some rational for the prepare/enable > split I can only direct them to mail archive posts since this is nowhere > to be found in the kernel. > > The comments in include/linux/clk.h, while correct, are very terse and > don't provide any insight to the reason why there is a split in the API. > > The content of Documentation/clk.txt does refer to prepare and enable > (and their counterparts) but again doesn't provide any clue about the > reason for their existence. > > Since there've been several good posts with usage example now buried > into list archives, I think this would go a long way helping people get > it right if those were part of the kernel documentation as well.
I'll update Documentation/clk.txt with more verbosity. The document was originally intended as a "porting guide" to help migrate from legacy frameworks to the common struct clk implementation. However the scope of the document should probably be generalized a bit more. Regards, Mike > > > Nicolas _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
