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56942fec06
The current timer-based delay loop relies on the architected timer to initiate the switch away from the polling-based implementation. This is unfortunate for platforms without the architected timers but with a suitable delay source (that is, constant frequency, always powered-up and ticking as long as the CPUs are online). This patch introduces a registration mechanism for the delay timer (which provides an unconditional read_current_timer implementation) and updates the architected timer code to use the new interface. Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Jonathan Austin <jonathan.austin@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
90 lines
2.3 KiB
C
90 lines
2.3 KiB
C
/*
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* Delay loops based on the OpenRISC implementation.
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*
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* Copyright (C) 2012 ARM Limited
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Author: Will Deacon <will.deacon@arm.com>
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*/
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#include <linux/delay.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/timex.h>
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/*
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* Default to the loop-based delay implementation.
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*/
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struct arm_delay_ops arm_delay_ops = {
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.delay = __loop_delay,
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.const_udelay = __loop_const_udelay,
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.udelay = __loop_udelay,
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};
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static const struct delay_timer *delay_timer;
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static bool delay_calibrated;
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int read_current_timer(unsigned long *timer_val)
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{
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if (!delay_timer)
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return -ENXIO;
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*timer_val = delay_timer->read_current_timer();
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return 0;
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}
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static void __timer_delay(unsigned long cycles)
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{
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cycles_t start = get_cycles();
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while ((get_cycles() - start) < cycles)
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cpu_relax();
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}
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static void __timer_const_udelay(unsigned long xloops)
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{
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unsigned long long loops = xloops;
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loops *= loops_per_jiffy;
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__timer_delay(loops >> UDELAY_SHIFT);
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}
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static void __timer_udelay(unsigned long usecs)
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{
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__timer_const_udelay(usecs * UDELAY_MULT);
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}
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void __init register_current_timer_delay(const struct delay_timer *timer)
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{
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if (!delay_calibrated) {
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pr_info("Switching to timer-based delay loop\n");
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delay_timer = timer;
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lpj_fine = timer->freq / HZ;
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loops_per_jiffy = lpj_fine;
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arm_delay_ops.delay = __timer_delay;
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arm_delay_ops.const_udelay = __timer_const_udelay;
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arm_delay_ops.udelay = __timer_udelay;
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delay_calibrated = true;
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} else {
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pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
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}
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}
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unsigned long __cpuinit calibrate_delay_is_known(void)
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{
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delay_calibrated = true;
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return lpj_fine;
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}
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