Quoting Stephen Boyd (2018-08-23 11:25:41) > Quoting Taniya Das (2018-08-22 03:28:31) > > > > > > > > Hmmmm. Ok. That won't work then. recalc_rate() better not try to > > > populate the frequency table then or it will not work. So I suppose it > > > needs to fallback to reading the registers and assuming the parent_rate > > > coming in is the actual frequency of it's parent until the frequency > > > table pointer is non-NULL. Would that work? > > > > > Yes that would work. > > Ok. > > > > > > BTW, does DFS switch parents without software knowing about it? > > DFS would not switch until a HW request is sent, but SW would be unware > > of the switch except the current_perf_state being updated with the > > requested level. > > > > What > > > happens in that case? Does the QUP driver make sure that the new parent > > > of this RCG is properly enabled so that it can switch to it when needed? > > > > I am not sure if they poll for any of their QUP HW state to make sure > > the switch is complete. > > > > > I'm still trying to understand this whole design. Who takes care of the > > > voltage requirements in this case? The QUP driver as well? > > > > > > > When the QUP driver requires to switch to new performance level, the > > first request would be to set_rate()(QUP driver would get the list of > > supported frequencies using the clk_round_rate()) which in QCOM clock > > driver would take care of setting the required voltage for the new > > parent switch. > > It would also make sure that the new parent is enabled if the QUP clk is > enabled. That's another concern. Does the PLL turn on automatically when > the RCG switches to it? > > > Then the QUP driver would request the HW for a new perf switch which > > would result to a DFS switch for the QUP clocks. > > It sounds like the QUP driver does half of the work via the clk APIs and > then the other half through the DFS register. Maybe the QUP driver > should be registering a clk as well for its DFS register so it can all > be clk API calls here. Something to consider. Anyway, that's not > important to this patch so here's the updated patch. I've squashed this in and applied the patches.
