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https://github.com/edk2-porting/linux-next.git
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70264367a2
When udelay() is implemented using an architected timer, it is wrong to scale loops_per_jiffy when changing the CPU clock frequency since the timer clock remains constant. The lpj should probably become an implementation detail relevant to the CPU loop based delay routine only and more confined to it. In the mean time this is the minimal fix needed to have expected delays with the timer based implementation when cpufreq is also in use. Reported-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Tested-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Liviu Dudau <Liviu.Dudau@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
92 lines
2.4 KiB
C
92 lines
2.4 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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EXPORT_SYMBOL_GPL(read_current_timer);
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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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arm_delay_ops.const_clock = true;
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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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