On Mon, Dec 16, 2019 at 05:11:32PM +0200, Peter De Schrijver wrote: > External email: Use caution opening links or attachments > > > On Mon, Dec 16, 2019 at 05:23:23PM +0300, Dmitry Osipenko wrote: > > >> Could you please clarify what do you mean by the "existing users"? > > >> AFAIK, nothing in kernel uses mux clocks. > > > > > > The DT clk bindings allow for parent initialization, so it's certainly > > > possible there are some DTs which rely on this. We promised to never > > > break the bindings, which changing to 1 clock would do. > > > > What about this variant: > > > > 1. Keep the old CaR code in place. > > > > 2. Make CaR driver to scan whole device-tree for the legacy PMC clocks. > > > > 3. If legacy clock is found, then register PMC clocks from CaR. > > > > 4. If legacy clocks are not found, then don't register PMC clocks from > > CaR. > > > > 5. Add clocks support to the PMC driver and only register them if > > legacy clocks are not registered by CaR. > > > > Now both old and new DTBs can co-exist and work, everyone happy. > > That seems even more work.. Today the only upstream user is audio. > Currently these clocks are setup by the CAR clock driver. However > as they will move to the PMC driver, this mechanism cannot be used. > Hence the plan is to modify the audio driver to check for the PMC clocks > in DT and if they are not available use the CAR clocks as fallback. > The whole reason the clocks move to the PMC driver, is that when PMC > becomes secure, all accesses have to go via an SMC. Given that we don't > want SMCs all over the Tegra drivers, it's a good opportunity to move > the PMC clock handling into the PMC driver. PMC can be secure with both > 'new' and old DTs, so just registering the PMC clocks in the CAR driver > if legacy clocks are found in the DT, won't always work. > Given the audio driver needs to change anyway, we can indeed use 1 clock per PMC clk_out_ rather than 2 as we have today. As this models the hw slightly better, I think we should do that as you suggested. Peter.
