On Tue, Aug 26, 2014 at 5:35 PM, Andrew Lunn <and...@lunn.ch> wrote: >> One final thought I have had is that it might be a good idea to have a >> mux clock which represents the clock signal that feeds into the cpu. It >> seems that a mux is exactly what is going on here with cpuclk rate and >> ddrclk rate. > > I did think of this when i implemented the cpufreq driver. What makes > it hard is that this bit is mixed in the same 32 bit register as the > gate clocks. It would mean two clock providers sharing the same > register, sharing a spinlock, etc. And the gating provider is shared > with all mvebu platforms, dove, kirkword, orion5x, and four different > armada SoCs. So i'm pushing complexity into this shared code, which > none of the others need. Does the standard mux clock do what is > needed? Or would i have to write a new clock provider?
Well I think that the mux-clock type should suffice. Both the standard gate and mux can have a spinlock passed in at registration-time, so it could be a shared spinlock. The standard mux clock expects a bitfield in a register, similar to the single-bit approach taken by the gate clock. So I think it could do just fine. > >> I even wonder if it is even appropriate to model this transition with a >> clock enable operation? Maybe it is only a multiplex operation, or >> perhaps a combination of enabling the powersave clock and changing the >> parent input to the cpu? >> >> My idea is instead of relying on a cpufreq driver to parse the state of >> your clocks and understand the multiplexing, you can use the clock >> framework for that. In fact that might help you get one step closer to >> using the cpufreq-cpu0.c/cpufreq-generic.c implementation. > > So you want the whole disabling of interrupt delivery to the cpu, > flipping the mux, wait for interrupt and re-enabling of interrupt > delivery to the cpu inside the clock provider? That is way past a > simple mux clock. No way! I said, "one step closer" for a reason. The interrupt stuff is clearly out of scope. Regards, Mike > > Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
