5b9b849b45
description was eaten by the dog (or an editor crash or something). Add variable-frequency support to the arm mpcore eventtimer driver. This allows a platform's early init code to tell the mpcore driver that the clock frequency can vary. That causes the mpcore driver to register an eventtimer, but not a timecounter. The platform has to provide a time counter using some other fixed-frequency clock, but can still use the per-cpu goodness of the mpcore hardware for event timers. When the platform support code does something to change the frequency of the CPU clocks (power saving, thermal management) it must tell the mpcore driver code about it using arm_tmr_change_frequency().
48 lines
2.0 KiB
C
48 lines
2.0 KiB
C
/*-
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* Copyright (c) 2014 Ian Lepore <ian@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _ARM_MPCORE_TIMERVAR_H_
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#define _ARM_MPCORE_TIMERVAR_H_
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/*
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* This value, passed to arm_tmr_change_frequency() any time before the mpcore
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* timer device attaches, informs the driver that the mpcore clock frequency can
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* change on the fly, and thus can't be used as a timecounter. The hardware can
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* still be used as an eventtimer, as long as each frequency change is
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* communicated to it with calls to arm_tmr_change_frequency().
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*/
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#define ARM_TMR_FREQUENCY_VARIES -1ULL
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/*
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* Inform the mpcore timer driver of a new clock frequency. This can be called
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* both before and after the mpcore timer driver attaches.
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*/
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void arm_tmr_change_frequency(uint64_t newfreq);
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#endif
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