Messages in this thread | | | Date | Mon, 29 Sep 2014 09:12:26 -0400 | From | Christopher Covington <> | Subject | Re: [PATCH v3] clocksource: arch_timer: Allow the device tree to specify the physical timer |
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Hi Doug,
On 09/11/2014 01:00 PM, Doug Anderson wrote: > Some 32-bit (ARMv7) systems are architected like this: > > * The firmware doesn't know and doesn't care about hypervisor mode and > we don't want to add the complexity of hypervisor there. > > * The firmware isn't involved in SMP bringup or resume. > > * The ARCH timer come up with an uninitialized offset between the > virtual and physical counters. Each core gets a different random > offset. > > * The device boots in "Secure SVC" mode.
I believe this can safely be detected by whether a write to CNTFRQ succeeds (handling the UNDEF on failure). I've tested this approach in what I've determined to be the 19 valid combinations of the following options.
* AArch64 EL3, AArch32 EL3, no EL3 * AArch64 EL2, AArch32 EL2, no EL2 * Start in SVC_N, SVC_S, HYP_N, MON_S
Christopher
-- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation.
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