85 lines
2.2 KiB
Text
85 lines
2.2 KiB
Text
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* ARM architected timer
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ARM cores may have a per-core architected timer, which provides per-cpu timers,
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or a memory mapped architected timer, which provides up to 8 frames with a
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physical and optional virtual timer per frame.
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The per-core architected timer is attached to a GIC to deliver its
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per-processor interrupts via PPIs. The memory mapped timer is attached to a GIC
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to deliver its interrupts via SPIs.
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** CP15 Timer node properties:
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- compatible : Should at least contain one of
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"arm,armv7-timer"
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"arm,armv8-timer"
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- interrupts : Interrupt list for secure, non-secure, virtual and
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hypervisor timers, in that order.
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- clock-frequency : The frequency of the main counter, in Hz. Optional.
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- always-on : a boolean property. If present, the timer is powered through an
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always-on power domain, therefore it never loses context.
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Example:
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timer {
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compatible = "arm,cortex-a15-timer",
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"arm,armv7-timer";
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interrupts = <1 13 0xf08>,
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<1 14 0xf08>,
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<1 11 0xf08>,
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<1 10 0xf08>;
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clock-frequency = <100000000>;
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};
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** Memory mapped timer node properties:
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- compatible : Should at least contain "arm,armv7-timer-mem".
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- clock-frequency : The frequency of the main counter, in Hz. Optional.
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- reg : The control frame base address.
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Note that #address-cells, #size-cells, and ranges shall be present to ensure
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the CPU can address a frame's registers.
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A timer node has up to 8 frame sub-nodes, each with the following properties:
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- frame-number: 0 to 7.
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- interrupts : Interrupt list for physical and virtual timers in that order.
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The virtual timer interrupt is optional.
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- reg : The first and second view base addresses in that order. The second view
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base address is optional.
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- status : "disabled" indicates the frame is not available for use. Optional.
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Example:
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timer@f0000000 {
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compatible = "arm,armv7-timer-mem";
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#address-cells = <1>;
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#size-cells = <1>;
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ranges;
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reg = <0xf0000000 0x1000>;
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clock-frequency = <50000000>;
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frame@f0001000 {
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frame-number = <0>
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interrupts = <0 13 0x8>,
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<0 14 0x8>;
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reg = <0xf0001000 0x1000>,
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<0xf0002000 0x1000>;
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};
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frame@f0003000 {
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frame-number = <1>
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interrupts = <0 15 0x8>;
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reg = <0xf0003000 0x1000>;
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status = "disabled";
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};
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};
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