On 13 May 2013 20:57, Mike Turquette <mturque...@linaro.org> wrote: > Quoting James Hogan (2013-04-19 09:28:21) >> This patchset adds support for automatic selection of the best parent >> for a clock mux, i.e. the one which can provide the closest clock rate >> to that requested. It can be controlled by a new CLK_SET_RATE_REMUX flag >> so that it doesn't happen unless explicitly allowed. >> > > I'm not sure about the new flag. One of my regrets during the early > development of the common struct clk is the CLK_SET_RATE_PARENT flag. > In hindsight I would have preferred to make parent-propagation of rate > changes the default behavior, and instead provide a flag to prevent that > behavior, such as CLK_SET_RATE_NO_PROPAGATE. > > One reason for this is the difficulty some have had with setting flags > from DT bindings.
Could you elaborate on this? I've been adding flags to DT bindings for this sort of thing, but it feels a bit like it's in that grey area of not really describing the hardware itself. This information needs to be specified somehow though. > Another reason is that a core goal of the framework > is to remove topology info from drivers; having to set a flag explicitly > on each clock to propagate rate changes is an impediment to that goal. (Something that I have found also where CLK_SET_RATE_PARENT doesn't fit well is when you have a mux where you want the set_rate propagated to one possible parent (e.g. a dedicated PLL) but not the other (e.g. the system clock - which happens to be a divider). In this case what I really want to say is "don't change the rate of this particular clock", in fact I added a CLK_DIVIDER_READ_ONLY divider flag locally for this purpose. Was there a particular use case of CLK_SET_RATE_PARENT where you'd want a clock to be changed from one child but not another?) > > So perhaps CLK_SET_RATE_REMUX is a similar situation. What do you think > about making remuxing the default and providing a flag to prevent it? Yes, fine by me. > And also we can assume for the immediate future that users of > .determine_rate WANT to remux, since .round_rate won't do it. Though > eventually it might be wise to convert all users of .round_rate over to > .determine_rate and deprecate .round_rate entirely. True. Cheers James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
