[PATCH v11 03/14] arm64/delay: move some constants out to a separate header

Ankur Arora
2026-04-08T12:26:32Z

Moves some constants and functions related to xloops, cycles computation
out to a new header. Also make __delay_cycles() available outside of
arch/arm64/lib/delay.c.

Rename some macros in qcom/rpmh-rsc.c which were occupying the same
namespace.

No functional change.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konradybcio@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Reviewed-by: Christoph Lameter <cl@linux.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
arch/arm64/include/asm/delay-const.h | 27 +++++++++++++++++++++++++++
arch/arm64/lib/delay.c | 15 ++++-----------
drivers/soc/qcom/rpmh-rsc.c | 8 ++++----
3 files changed, 35 insertions(+), 15 deletions(-)
create mode 100644 arch/arm64/include/asm/delay-const.h

diff --git a/arch/arm64/include/asm/delay-const.h b/arch/arm64/include/asm/delay-const.h
new file mode 100644
index 000000000000..cb3988ff4e41
--- /dev/null
+++ b/arch/arm64/include/asm/delay-const.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_DELAY_CONST_H
+#define _ASM_DELAY_CONST_H
+
+#include <asm/param.h> /* For HZ */
+
+/* 2**32 / 1000000 (rounded up) */
+#define __usecs_to_xloops_mult 0x10C7UL
+
+/* 2**32 / 1000000000 (rounded up) */
+#define __nsecs_to_xloops_mult 0x5UL
+
+extern unsigned long loops_per_jiffy;
+static inline unsigned long xloops_to_cycles(unsigned long xloops)
+{
+ return (xloops * loops_per_jiffy * HZ) >> 32;
+}
+
+#define USECS_TO_CYCLES(time_usecs) \
+ xloops_to_cycles((time_usecs) * __usecs_to_xloops_mult)
+
+#define NSECS_TO_CYCLES(time_nsecs) \
+ xloops_to_cycles((time_nsecs) * __nsecs_to_xloops_mult)
+
+u64 notrace __delay_cycles(void);
+
+#endif /* _ASM_DELAY_CONST_H */
diff --git a/arch/arm64/lib/delay.c b/arch/arm64/lib/delay.c
index e278e060e78a..c660a7ea26dd 100644
--- a/arch/arm64/lib/delay.c
+++ b/arch/arm64/lib/delay.c
@@ -12,17 +12,10 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timex.h>
+#include <asm/delay-const.h>

#include <clocksource/arm_arch_timer.h>

-#define USECS_TO_CYCLES(time_usecs) \
- xloops_to_cycles((time_usecs) * 0x10C7UL)
-
-static inline unsigned long xloops_to_cycles(unsigned long xloops)
-{
- return (xloops * loops_per_jiffy * HZ) >> 32;
-}
-
/*
* Force the use of CNTVCT_EL0 in order to have the same base as WFxT.
* This avoids some annoying issues when CNTVOFF_EL2 is not reset 0 on a
@@ -32,7 +25,7 @@ static inline unsigned long xloops_to_cycles(unsigned long xloops)
* Note that userspace cannot change the offset behind our back either,
* as the vcpu mutex is held as long as KVM_RUN is in progress.
*/
-static cycles_t notrace __delay_cycles(void)
+u64 notrace __delay_cycles(void)
{
guard(preempt_notrace)();
return __arch_counter_get_cntvct_stable();
@@ -73,12 +66,12 @@ EXPORT_SYMBOL(__const_udelay);

void __udelay(unsigned long usecs)
{
- __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
+ __const_udelay(usecs * __usecs_to_xloops_mult);
}
EXPORT_SYMBOL(__udelay);

void __ndelay(unsigned long nsecs)
{
- __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
+ __const_udelay(nsecs * __nsecs_to_xloops_mult);
}
EXPORT_SYMBOL(__ndelay);
diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index c6f7d5c9c493..ad5ec5c0de0a 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -146,10 +146,10 @@ enum {
* +---------------------------------------------------+
*/

-#define USECS_TO_CYCLES(time_usecs) \
- xloops_to_cycles((time_usecs) * 0x10C7UL)
+#define RPMH_USECS_TO_CYCLES(time_usecs) \
+ rpmh_xloops_to_cycles((time_usecs) * 0x10C7UL)

-static inline unsigned long xloops_to_cycles(u64 xloops)
+static inline unsigned long rpmh_xloops_to_cycles(u64 xloops)
{
return (xloops * loops_per_jiffy * HZ) >> 32;
}
@@ -819,7 +819,7 @@ void rpmh_rsc_write_next_wakeup(struct rsc_drv *drv)
wakeup_us = ktime_to_us(wakeup);

/* Convert the wakeup to arch timer scale */
- wakeup_cycles = USECS_TO_CYCLES(wakeup_us);
+ wakeup_cycles = RPMH_USECS_TO_CYCLES(wakeup_us);
wakeup_cycles += arch_timer_read_counter();

exit:
--
2.31.1