Hi Mark, On Fri, Nov 04, 2022 at 03:44:53PM +0000, Mark Brown wrote: > On Fri, Nov 04, 2022 at 02:18:00PM +0100, Maxime Ripard wrote: > > > So, the set_parent hook is effectively unused, possibly because of an > > oversight. However, it could also be an explicit decision by the > > original author to avoid any reparenting but through an explicit call to > > clk_set_parent(). > > > The latter case would be equivalent to setting the flag > > CLK_SET_RATE_NO_REPARENT, together with setting our determine_rate hook > > to __clk_mux_determine_rate(). Indeed, if no determine_rate > > implementation is provided, clk_round_rate() (through > > clk_core_round_rate_nolock()) will call itself on the parent if > > CLK_SET_RATE_PARENT is set, and will not change the clock rate > > otherwise. __clk_mux_determine_rate() has the exact same behavior when > > CLK_SET_RATE_NO_REPARENT is set. > > > And if it was an oversight, then we are at least explicit about our > > behavior now and it can be further refined down the line. > > Given that the current approach involves patching every single user to > set a default implementation it feels like it might be more > straightforward to just have the clock API use that implementation if > none is defined - as you say there's already a flag to indicate the > unusual case where there's a solid reason to prevent reparenting. It > feels like the resulting API is more straightforward. That would be another solution indeed. The thing is, most places where determine_rate is missing seems to be oversight, and the flag is missing as well. Just filling determine_rate if it's missing with __clk_mux_determine_rate will possibly pick different parents, and I'm fairly certain that this have never been tested on most platforms, and will be completely broken. And I don't really want to play a game of whack-a-mole adding that flag everywhere it turns out it's broken. Maxime
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