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Sumit GargandSumit Garg
ccf67965e1
On AArch64, secure world has it's own EL3 physical timer registers accessible to secure EL1 in absence of S-EL2. With S-EL2 there is virtualized view available for EL1 timer registers. So it is unreasonable for secure world to use non-secure EL1 physical timer registers. Moreover, the non-secure operating system (Linux in our case) relies heavily on these EL1 physical timer registers for scheduling decisions. If NS_TIMER_SWITCH is enabled, it simply breaks the preemption model of the non-secure world by disabling non-secure timer interrupts leading to RCU stalls being observed on long running secure world tasks. The only arch timer register which will benefit from context management is cntkctl_el1: Counter-timer Kernel Control Register. This enables the secure and non-secure worlds to independently control accesses to EL0 for counter-timer registers. This is something that OP-TEE uses to enable ftrace feature for Trusted Applications and SPM_MM uses for EL0 access as well. Lets enable context management of cntkctl_el1 by default and deprecate conditional context management of non-secure EL1 physical timer registers for whom there isn't any upstream user. With that deprecate this NS_TIMER_SWITCH build option which just adds confusion for the platform maintainers. It will be eventually dropped following deprecation policy of TF-A. Reported-by: Stauffer Thomas MTANA <thomas.stauffer@mt.com> Reported-by: Andrew Davis <afd@ti.com> Change-Id: Ifb3a919dc0bf8c05c38895352de5fe94b4f4387e Signed-off-by: Sumit Garg <sumit.garg@oss.qualcomm.com>