[PATCH v16 03/16] arm64/delay: move, fixup usecs_to_cycles()

[Ankur Arora <ankur.a.arora@oracle.com>]

Update xloops_to_cycles() to use mul_u64_u64_shr() instead of 32-bit fixed point
arithmetic to avoid truncation for delay values larger than ~10s
This adds an extra mul operation but is only used from delay loops so
shouldn't matter too much.

Also move some related constants and functions related to the cycles
computation out to a new header (converting some from macros to static
inlines). And finally 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.

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>
---
Notes:
  - Make USECS_TO_CYCLES() into a static inline rpmh_usecs_to_cycles()

 arch/arm64/include/asm/delay-const.h | 35 ++++++++++++++++++++++++++++
 arch/arm64/lib/delay.c               | 17 ++++----------
 drivers/soc/qcom/rpmh-rsc.c          | 12 ++++++----
 3 files changed, 47 insertions(+), 17 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..6ccdfe0a4130
--- /dev/null
+++ b/arch/arm64/include/asm/delay-const.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_DELAY_CONST_H
+#define _ASM_DELAY_CONST_H
+
+#include <linux/math64.h>
+#include <linux/types.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 u64 xloops_to_cycles(u64 xloops)
+{
+	u64 loops_per_sec = (u64)loops_per_jiffy * HZ;
+
+	return mul_u64_u64_shr(xloops, loops_per_sec, 32);
+}
+
+static inline u64 usecs_to_cycles(u64 time_usecs)
+{
+	return xloops_to_cycles(time_usecs * __usecs_to_xloops_mult);
+}
+
+static inline u64 nsecs_to_cycles(u64 time_nsecs)
+{
+	return 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..f08eacef2f0a 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();
@@ -54,7 +47,7 @@ void __delay(unsigned long cycles)
 			wfet(end);
 	} else 	if (arch_timer_evtstrm_available()) {
 		const cycles_t timer_evt_period =
-			USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);
+			usecs_to_cycles(ARCH_TIMER_EVT_STREAM_PERIOD_US);
 
 		while ((__delay_cycles() - start + timer_evt_period) < cycles)
 			wfe();
@@ -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 f881af35ecfc..dabe0ccba370 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -146,14 +146,16 @@ enum {
  *  +---------------------------------------------------+
  */
 
-#define USECS_TO_CYCLES(time_usecs)			\
-	xloops_to_cycles((time_usecs) * 0x10C7UL)
-
-static inline unsigned long xloops_to_cycles(u64 xloops)
+static inline u64 rpmh_xloops_to_cycles(u64 xloops)
 {
 	return (xloops * loops_per_jiffy * HZ) >> 32;
 }
 
+static inline u64 rpmh_usecs_to_cycles(u64 time_usecs)
+{
+	return rpmh_xloops_to_cycles((time_usecs) * 0x10C7UL);
+}
+
 static u32 rpmh_rsc_reg_offset_ver_2_7[] = {
 	[RSC_DRV_TCS_OFFSET]		= 672,
 	[RSC_DRV_CMD_OFFSET]		= 20,
@@ -828,7 +830,7 @@ 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:
-- 
2.43.7