1 files changed, 129 insertions, 0 deletions
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c
new file mode 100644
index 000000000..d4aa10795
--- /dev/null
+++ b/arch/s390/lib/delay.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *    Precise Delay Loops for S390
+ *
+ *    Copyright IBM Corp. 1999, 2008
+ *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
+ *		 Heiko Carstens <heiko.carstens@de.ibm.com>,
+ */
+
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/timex.h>
+#include <linux/export.h>
+#include <linux/irqflags.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <asm/vtimer.h>
+#include <asm/div64.h>
+#include <asm/idle.h>
+
+void __delay(unsigned long loops)
+{
+        /*
+         * To end the bloody studid and useless discussion about the
+         * BogoMips number I took the liberty to define the __delay
+         * function in a way that that resulting BogoMips number will
+         * yield the megahertz number of the cpu. The important function
+         * is udelay and that is done using the tod clock. -- martin.
+         */
+	asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
+}
+EXPORT_SYMBOL(__delay);
+
+static void __udelay_disabled(unsigned long long usecs)
+{
+	unsigned long cr0, cr0_new, psw_mask;
+	struct s390_idle_data idle;
+	u64 end;
+
+	end = get_tod_clock() + (usecs << 12);
+	__ctl_store(cr0, 0, 0);
+	cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK;
+	cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */
+	__ctl_load(cr0_new, 0, 0);
+	psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT;
+	set_clock_comparator(end);
+	set_cpu_flag(CIF_IGNORE_IRQ);
+	psw_idle(&idle, psw_mask);
+	clear_cpu_flag(CIF_IGNORE_IRQ);
+	set_clock_comparator(S390_lowcore.clock_comparator);
+	__ctl_load(cr0, 0, 0);
+}
+
+static void __udelay_enabled(unsigned long long usecs)
+{
+	u64 clock_saved, end;
+
+	end = get_tod_clock_fast() + (usecs << 12);
+	do {
+		clock_saved = 0;
+		if (tod_after(S390_lowcore.clock_comparator, end)) {
+			clock_saved = local_tick_disable();
+			set_clock_comparator(end);
+		}
+		enabled_wait();
+		if (clock_saved)
+			local_tick_enable(clock_saved);
+	} while (get_tod_clock_fast() < end);
+}
+
+/*
+ * Waits for 'usecs' microseconds using the TOD clock comparator.
+ */
+void __udelay(unsigned long long usecs)
+{
+	unsigned long flags;
+
+	preempt_disable();
+	local_irq_save(flags);
+	if (in_irq()) {
+		__udelay_disabled(usecs);
+		goto out;
+	}
+	if (in_softirq()) {
+		if (raw_irqs_disabled_flags(flags))
+			__udelay_disabled(usecs);
+		else
+			__udelay_enabled(usecs);
+		goto out;
+	}
+	if (raw_irqs_disabled_flags(flags)) {
+		local_bh_disable();
+		__udelay_disabled(usecs);
+		_local_bh_enable();
+		goto out;
+	}
+	__udelay_enabled(usecs);
+out:
+	local_irq_restore(flags);
+	preempt_enable();
+}
+EXPORT_SYMBOL(__udelay);
+
+/*
+ * Simple udelay variant. To be used on startup and reboot
+ * when the interrupt handler isn't working.
+ */
+void udelay_simple(unsigned long long usecs)
+{
+	u64 end;
+
+	end = get_tod_clock_fast() + (usecs << 12);
+	while (get_tod_clock_fast() < end)
+		cpu_relax();
+}
+
+void __ndelay(unsigned long long nsecs)
+{
+	u64 end;
+
+	nsecs <<= 9;
+	do_div(nsecs, 125);
+	end = get_tod_clock_fast() + nsecs;
+	if (nsecs & ~0xfffUL)
+		__udelay(nsecs >> 12);
+	while (get_tod_clock_fast() < end)
+		barrier();
+}
+EXPORT_SYMBOL(__ndelay);