From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel.lezcano@linaro.org (Daniel Lezcano) Date: Mon, 20 Jan 2014 15:42:10 +0100 Subject: [PATCH] arch_timer: Move delay timer to drivers clocksource In-Reply-To: <52D97831.6030700@codeaurora.org> References: <1389791227-24097-1-git-send-email-pgaikwad@nvidia.com> <20140115154526.GC3571@mudshark.cambridge.arm.com> <52D76BC8.6080405@nvidia.com> <20140116121649.GG30257@mudshark.cambridge.arm.com> <878uufyo13.fsf@iki.fi> <52D8F403.9070602@linaro.org> <52D901B6.1070800@nvidia.com> <52D902D6.3090208@linaro.org> <52D915F3.3030500@nvidia.com> <52D91D3A.80800@linaro.org> <52D932B5.7020909@nvidia.com> <52D97831.6030700@codeaurora.org> Message-ID: <52DD35C2.3070809@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 01/17/2014 07:36 PM, Stephen Boyd wrote: > On 01/17/14 05:40, Prashant Gaikwad wrote: >> >> Another requirement: >> >> We have 3 timers T1, T2, T3 used as wake events for 3 idle states C1, >> C2, C3 respectively. >> >> Rating of T2 is better than T3. If I register T2 and T3 both as >> broadcast timers then T3 will not be used. But ... >> - T2 is not preserved in C3 idle state. >> - T3 resolution is very poor (ms) and can not be used as wake >> event for C2. >> >> Possible solution, register only T3 as broadcast device and use T2 as >> per-CPU fallback timer. > > We have the same situation on MSM. I've been thinking about proposing we > allow multiple broadcast timers to exist in the system and then have the > clockevents_notify() caller indicate which C state is being entered. The > broadcast timers would need to indicate which C state they don't work in > though. IMO, there are different solutions: 1. extend the C3STOP to C1STOP, C2STOP, etc ... and pass the idle state to the time framework where these flags are checked against. I don't like this approach but it is feasible. 2. use the generic power domain. When the power domain is shutdown via the cpuidle backend driver, it switches the timer. -- Linaro.org ? Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog