4155fc07fa
The ARM Generic Timer (AKA the architected timer, arm_arch_timer) features a CPU register (CNTFRQ) which firmware is intended to initialize, and non-secure software can read to determine the frequency of the timer. On CPUs with secure state, this register cannot be written from non-secure states. The firmware of early SoCs featuring the timer did not correctly initialize CNTFRQ correctly on all CPUs, requiring the frequency to be described in DT as a workaround. This workaround is not complete however as it is exposed to all software in a privileged non-secure mode (including guests running under a hypervisor). The firmware and DTs for recent SoCs have followed the example set by these early SoCs. This patch updates the arch timer binding documentation to make it clearer that the use of the clock-frequency property is a poor work-around. The MMIO generic timer binding is similarly updated, though this is less of a concern as there is generally no need to expose the MMIO timers to guest OSs. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Marc Zyngier <marc.zyngier@arm.com> Acked-by: Olof Johansson <olof@lixom.net> Acked-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Rob Herring <robh+dt@kernel.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Rob Herring <robh@kernel.org> |
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| .. | ||
| bindings | ||
| 00-INDEX | ||
| booting-without-of.txt | ||
| changesets.txt | ||
| dynamic-resolution-notes.txt | ||
| of_unittest.txt | ||
| overlay-notes.txt | ||
| todo.txt | ||
| usage-model.txt | ||