[PATCH v2 1/3] drivers: clocksource: configure event stream for ARM arch timer
From: catalin.marinas@arm.com (Catalin Marinas)
Date: 2013-07-23 10:24:10
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On Mon, Jul 22, 2013 at 12:21:20PM +0100, Sudeep KarkadaNagesha wrote:
From: Will Deacon <redacted> The ARM architected timer can generate events (used for waking up CPUs executing the wfe instruction) at a frequency represented as a power-of-2 divisor of the clock rate. This patch configures the event stream, aiming for a period of 100us between events. This can be used to implement wfe-based timeouts for userspace locking implementations.
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quoted hunk ↗ jump to hunk
--- a/include/clocksource/arm_arch_timer.h +++ b/include/clocksource/arm_arch_timer.h@@ -29,6 +29,8 @@ #define ARCH_TIMER_PHYS_ACCESS 0 #define ARCH_TIMER_VIRT_ACCESS 1 +#define ARCH_TIMER_EVT_STREAM_FREQ 10000 /* 100us */
BTW, if user-space starts using this, it will become an ABI. Is this the right frequency? In addition, do we want to expose this via hwcap? Something like HWCAP_EVSTR100US? -- Catalin