Hi, On Fri, Mar 11, 2022 at 07:08:39PM -0800, Stephen Boyd wrote: > Quoting Maxime Ripard (2022-02-25 06:35:22) > > Hi, > > > > This is a follow-up of the discussion here: > > https://lore.kernel.org/linux-clk/20210319150355.xzw7ikwdaga2dwhv@gilmour/ > > > > and here: > > https://lore.kernel.org/all/20210914093515.260031-1-maxime@xxxxxxxxxx/ > > > > While the initial proposal implemented a new API to temporarily raise and lower > > clock rates based on consumer workloads, Stephen suggested an > > alternative approach implemented here. > > > > The main issue that needed to be addressed in our case was that in a > > situation where we would have multiple calls to clk_set_rate_range, we > > would end up with a clock at the maximum of the minimums being set. This > > would be expected, but the issue was that if one of the users was to > > relax or drop its requirements, the rate would be left unchanged, even > > though the ideal rate would have changed. > > > > So something like > > > > clk_set_rate(user1_clk, 1000); > > clk_set_min_rate(user1_clk, 2000); > > clk_set_min_rate(user2_clk, 3000); > > clk_set_min_rate(user2_clk, 1000); > > > > Would leave the clock running at 3000Hz, while the minimum would now be > > 2000Hz. > > > > This was mostly due to the fact that the core only triggers a rate > > change in clk_set_rate_range() if the current rate is outside of the > > boundaries, but not if it's within the new boundaries. > > > > That series changes that and will trigger a rate change on every call, > > with the former rate being tried again. This way, providers have a > > chance to follow whatever policy they see fit for a given clock each > > time the boundaries change. > > > > This series also implements some kunit tests, first to test a few rate > > related functions in the CCF, and then extends it to make sure that > > behaviour has some test coverage. > > > > Let me know what you think > > Thanks. I'm going to apply this to clk-next but not the last two drm > patches. That is OK? Yes, that will be perfect, thanks! Maxime
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