On Thu, 25 Nov 2021 at 15:13, Maulik Shah <quic_mkshah@xxxxxxxxxxx> wrote: > > Hi Peter, > > On 11/25/2021 3:21 PM, Peter Zijlstra wrote: > > On Thu, Nov 25, 2021 at 02:44:36PM +0530, Maulik Shah wrote: > >> Export cpu_idle_poll_ctrl() so that module drivers can use same. > > This does not seem like a really safe interface to expose to the > > world. > > Thanks for the review. > > Keeping the cpuidle enabled from boot up may delay/increase the boot up > time. > Below is our use case to force cpuidle to stay in cpu_idle_poll(). > > We keep cpuidle disabled from boot up using "nohlt" option of kernel > command line which internally sets cpu_idle_force_poll = 1; > and once the device bootup reaches till certain point (for example the > android homescreen is up) userspace may notify a > vendor module driver which can invoke cpu_idle_poll_ctrl(false); to come > out of poll mode. > So vendor module driver needs cpu_idle_poll_ctrl() exported symbol. Waiting for the homescreen can be considered as rather late, from the kernel boot progress point of view. That said, I am wondering if a similar improvement can be achieved by just allowing WFI (thus no deeper idle states) until homescreen? If so, that can be quite easily achieved by modularizing the cpuidle-psci driver. [...] Kind regards Uffe
