Mike, On Wed, Nov 19, 2014 at 6:30 PM, Mike Turquette <mturquette at linaro.org> wrote: > Quoting Doug Anderson (2014-11-07 17:06:58) >> With the existing code, if you find a parent for an orhpan that has >> already been prepared / enabled, you won't enable the parent. That >> can cause later problems since the clock tree isn't in a consistent >> state. Fix by propagating the prepare and enable. >> >> NOTE: this does bring up the question about whether the enable of the >> orphan actually made sense. If the orphan's parent wasn't enabled by >> default (by the bootloader or the default state of the hardware) then >> the original enable of the orphan probably didn't do what the caller >> though it would. Some users of the orphan might have preferred an >> EPROBE_DEFER be returned until we had a full path to a root clock. >> This patch doesn't address those concerns and really just syncs up the >> state. > > -ECANOFWORMS > > I'm thinking about this patch but I haven't quite made up my mind. It is > reasonable, but also some nice kind of error might be preferable when > preparing/enabling an orphaned clock. > > Under what conditions might a clock be orphaned? An obvious example is > just bad luck during the thundering herd of clock registrations from a > driver. In this case deferring the probe might be a good idea. > > However what about the case where a loadable module provides the parent > clock? It might be a long time before the orphan clocks gets picked up > from the orphanage. Is deferring probe the right thing here as well? I will defer to your wisdom here. I agree that these are the two primary solutions and I've picked one, but I have no idea which will be more of a PITA in the long run. Note: I'm not sure that anyone expects EPROBE_DEFER to be returned from a clk_enable() (do they?). It almost seems like the right answer is to fail to allow anyone to clk_get() any clock that doesn't have a path to root. I will say that without this patch or the EPROBE_DEFER solution we have a clear bug. You can get into a situation where a clock is enabled/prepared but its parent isn't. -Doug
