On 12/12/22 18:37, Stephen Boyd wrote: > Quoting Sean Anderson (2022-12-08 07:36:45) >> On 12/6/22 21:17, Stephen Boyd wrote: >> > Quoting Sean Anderson (2022-11-01 16:27:21) >> >> On 11/1/22 16:10, Stephen Boyd wrote: >> >> >> >> >> >> Oh, I remember why I did this. I need the reference clock for clk_hw_round_rate, >> >> >> which is AFAICT the only correct way to implement round_rate. >> >> >> >> >> > >> >> > Is the reference clk the parent of the clk implementing >> >> > clk_ops::round_rate()? >> >> >> >> Yes. We may be able to produce a given output with multiple reference >> >> rates. However, the clock API provides no mechanism to say "Don't ask >> >> for the parent clock to be rate X, you just tried it and the parent >> >> clock can't support it." So instead, we loop over the possible reference >> >> rates and pick the first one which the parent says it can round to. >> >> >> > >> > Sorry, I'm lost. Why can't you loop over possible reference rates in >> > determine_rate/round_rate clk op here? >> >> This is what I do currently, but you need to have the parent clock to do >> so. With your suggested method, we never actually get a struct clk(_hw) >> which we can query for rate support. > > The clk_hw for the parent is given to the determine_rate clk_op in the > clk_rate_request structure. It's stored in the best_parent_hw pointer > when the determine_rate function is called. Does that work for you? Huh, I didn't realize that best_parent_hw was an input as well as an output. The way it's documented, it makes it seem like this is set by determine_rate. I'm still not very happy with having to use an aux bus, as there are plenty of other drivers which just register clocks with the top-level device. I will try and revisit this at some point, but the project has ended so I'm not sure when I will find the time. --Sean
