Re: cpuidle future and improvements
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Daniel, On 06/18/2012 02:10 PM, Daniel Lezcano wrote:
Dear all, A few weeks ago, Peter De Schrijver proposed a patch  to allow per cpu latencies. We had a discussion about this patchset because it reverse the modifications Deepthi did some months ago  and we may want to provide a different implementation. The Linaro Connect  event bring us the opportunity to meet people involved in the power management and the cpuidle area for different SoC. With the Tegra3 and big.LITTLE architecture, making per cpu latencies for cpuidle is vital. Also, the SoC vendors would like to have the ability to tune their cpu latencies through the device tree. We agreed in the following steps: 1. factor out / cleanup the cpuidle code as much as possible 2. better sharing of code amongst SoC idle drivers by moving common bits to core code 3. make the cpuidle_state structure contain only data 4. add a API to register latencies per cpu These four steps impacts all the architecture. I began the factor out code / cleanup  and that has been accepted upstream and I proposed some modifications  but I had a very few answers.
Another thing which we discussed is bringing the CPU cluster/package notion in the core idle code. Couple idle did bring that idea to some extent but in can be further extended and absratcted. Atm, most of the work is done in back-end cpuidle drivers which can be easily abstracted if the "cluster idle" notion is supported in the core layer. Per CPU __and__ per operating point(OPP), latency is something which can be also added to the list. From the discussion I remember, it matters for few SoCs and can be beneficial. Regards Santosh