diff options
Diffstat (limited to 'arch/arm/lib/delay.c')
| -rw-r--r-- | arch/arm/lib/delay.c | 50 |
1 files changed, 31 insertions, 19 deletions
diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c index 64dbfa57204a..b7fe84f68bf1 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -1,24 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * Delay loops based on the OpenRISC implementation. * * Copyright (C) 2012 ARM Limited * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA - * * Author: Will Deacon <will.deacon@arm.com> */ +#include <linux/clocksource.h> #include <linux/delay.h> #include <linux/init.h> #include <linux/kernel.h> @@ -28,7 +17,7 @@ /* * Default to the loop-based delay implementation. */ -struct arm_delay_ops arm_delay_ops = { +struct arm_delay_ops arm_delay_ops __ro_after_init = { .delay = __loop_delay, .const_udelay = __loop_const_udelay, .udelay = __loop_udelay, @@ -36,6 +25,7 @@ struct arm_delay_ops arm_delay_ops = { static const struct delay_timer *delay_timer; static bool delay_calibrated; +static u64 delay_res; int read_current_timer(unsigned long *timer_val) { @@ -47,6 +37,11 @@ int read_current_timer(unsigned long *timer_val) } EXPORT_SYMBOL_GPL(read_current_timer); +static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift) +{ + return (cyc * mult) >> shift; +} + static void __timer_delay(unsigned long cycles) { cycles_t start = get_cycles(); @@ -69,25 +64,42 @@ static void __timer_udelay(unsigned long usecs) void __init register_current_timer_delay(const struct delay_timer *timer) { - if (!delay_calibrated) { - pr_info("Switching to timer-based delay loop\n"); + u32 new_mult, new_shift; + u64 res; + + clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq, + NSEC_PER_SEC, 3600); + res = cyc_to_ns(1ULL, new_mult, new_shift); + + if (res > 1000) { + pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n", + timer, res); + return; + } + + if (!delay_calibrated && (!delay_res || (res < delay_res))) { + pr_info("Switching to timer-based delay loop, resolution %lluns\n", res); delay_timer = timer; lpj_fine = timer->freq / HZ; + delay_res = res; /* cpufreq may scale loops_per_jiffy, so keep a private copy */ arm_delay_ops.ticks_per_jiffy = lpj_fine; arm_delay_ops.delay = __timer_delay; arm_delay_ops.const_udelay = __timer_const_udelay; arm_delay_ops.udelay = __timer_udelay; - - delay_calibrated = true; } else { pr_info("Ignoring duplicate/late registration of read_current_timer delay\n"); } } -unsigned long __cpuinit calibrate_delay_is_known(void) +unsigned long calibrate_delay_is_known(void) { delay_calibrated = true; return lpj_fine; } + +void calibration_delay_done(void) +{ + delay_calibrated = true; +} |