summaryrefslogtreecommitdiffstats
path: root/kernel/arch/arm/lib/delay.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/arch/arm/lib/delay.c')
-rw-r--r--kernel/arch/arm/lib/delay.c117
1 files changed, 117 insertions, 0 deletions
diff --git a/kernel/arch/arm/lib/delay.c b/kernel/arch/arm/lib/delay.c
new file mode 100644
index 000000000..8044591dc
--- /dev/null
+++ b/kernel/arch/arm/lib/delay.c
@@ -0,0 +1,117 @@
+/*
+ * 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>
+#include <linux/module.h>
+#include <linux/timex.h>
+
+/*
+ * Default to the loop-based delay implementation.
+ */
+struct arm_delay_ops arm_delay_ops = {
+ .delay = __loop_delay,
+ .const_udelay = __loop_const_udelay,
+ .udelay = __loop_udelay,
+};
+
+static const struct delay_timer *delay_timer;
+static bool delay_calibrated;
+static u64 delay_res;
+
+int read_current_timer(unsigned long *timer_val)
+{
+ if (!delay_timer)
+ return -ENXIO;
+
+ *timer_val = delay_timer->read_current_timer();
+ return 0;
+}
+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();
+
+ while ((get_cycles() - start) < cycles)
+ cpu_relax();
+}
+
+static void __timer_const_udelay(unsigned long xloops)
+{
+ unsigned long long loops = xloops;
+ loops *= arm_delay_ops.ticks_per_jiffy;
+ __timer_delay(loops >> UDELAY_SHIFT);
+}
+
+static void __timer_udelay(unsigned long usecs)
+{
+ __timer_const_udelay(usecs * UDELAY_MULT);
+}
+
+void __init register_current_timer_delay(const struct delay_timer *timer)
+{
+ 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;
+ } else {
+ pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
+ }
+}
+
+unsigned long calibrate_delay_is_known(void)
+{
+ delay_calibrated = true;
+ return lpj_fine;
+}
+
+void calibration_delay_done(void)
+{
+ delay_calibrated = true;
+}