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Message-ID: <20241105183041.1531976-4-harisokn@amazon.com>
Date: Tue, 5 Nov 2024 12:30:39 -0600
From: Haris Okanovic <harisokn@...zon.com>
To: <ankur.a.arora@...cle.com>, <catalin.marinas@....com>
CC: <linux-pm@...r.kernel.org>, <kvm@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
<will@...nel.org>, <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
<pbonzini@...hat.com>, <wanpengli@...cent.com>, <vkuznets@...hat.com>,
<rafael@...nel.org>, <daniel.lezcano@...aro.org>, <peterz@...radead.org>,
<arnd@...db.de>, <lenb@...nel.org>, <mark.rutland@....com>,
<harisokn@...zon.com>, <mtosatti@...hat.com>, <sudeep.holla@....com>,
<cl@...two.org>, <misono.tomohiro@...itsu.com>, <maobibo@...ngson.cn>,
<joao.m.martins@...cle.com>, <boris.ostrovsky@...cle.com>,
<konrad.wilk@...cle.com>
Subject: [PATCH 3/5] arm64: refactor delay() to enable polling for value
Refactor arm64's delay() to poll for a mask/value condition (vcond) in
it's wfet(), wfe(), and relaxed polling loops.
Signed-off-by: Haris Okanovic <harisokn@...zon.com>
---
arch/arm64/lib/delay.c | 70 ++++++++++++++++++++++++++++++------------
1 file changed, 50 insertions(+), 20 deletions(-)
diff --git a/arch/arm64/lib/delay.c b/arch/arm64/lib/delay.c
index cb2062e7e234..a7c3040af316 100644
--- a/arch/arm64/lib/delay.c
+++ b/arch/arm64/lib/delay.c
@@ -14,43 +14,73 @@
#include <linux/timex.h>
#include <clocksource/arm_arch_timer.h>
+#include <asm/readex.h>
-#define USECS_TO_CYCLES(time_usecs) \
- xloops_to_cycles((time_usecs) * 0x10C7UL)
-
-static inline unsigned long xloops_to_cycles(unsigned long xloops)
+static inline u64 xloops_to_cycles(u64 xloops)
{
return (xloops * loops_per_jiffy * HZ) >> 32;
}
-void __delay(unsigned long cycles)
+#define USECS_TO_XLOOPS(time_usecs) \
+ ((time_usecs) * 0x10C7UL)
+
+#define USECS_TO_CYCLES(time_usecs) \
+ xloops_to_cycles(USECS_TO_XLOOPS(time_usecs))
+
+#define NSECS_TO_XLOOPS(time_nsecs) \
+ ((time_nsecs) * 0x10C7UL)
+
+#define NSECS_TO_CYCLES(time_nsecs) \
+ xloops_to_cycles(NSECS_TO_XLOOPS(time_nsecs))
+
+static unsigned long __delay_until_ul(u64 cycles, unsigned long* addr, unsigned long mask, unsigned long val)
{
- cycles_t start = get_cycles();
+ u64 start = get_cycles();
+ unsigned long cur;
if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) {
u64 end = start + cycles;
- /*
- * Start with WFIT. If an interrupt makes us resume
- * early, use a WFET loop to complete the delay.
- */
- wfit(end);
- while ((get_cycles() - start) < cycles)
+ do {
+ cur = __READ_ONCE_EX(*addr);
+ if ((cur & mask) == val) {
+ break;
+ }
wfet(end);
- } else if (arch_timer_evtstrm_available()) {
- const cycles_t timer_evt_period =
+ } while ((get_cycles() - start) < cycles);
+ } else if (arch_timer_evtstrm_available()) {
+ const u64 timer_evt_period =
USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);
- while ((get_cycles() - start + timer_evt_period) < cycles)
+ do {
+ cur = __READ_ONCE_EX(*addr);
+ if ((cur & mask) == val) {
+ break;
+ }
wfe();
+ } while ((get_cycles() - start + timer_evt_period) < cycles);
+ } else {
+ do {
+ cur = __READ_ONCE_EX(*addr);
+ if ((cur & mask) == val) {
+ break;
+ }
+ cpu_relax();
+ } while ((get_cycles() - start) < cycles);
}
- while ((get_cycles() - start) < cycles)
- cpu_relax();
+ return cur;
+}
+
+void __delay(unsigned long cycles)
+{
+ /* constant word for wfet()/wfe() to poll */
+ unsigned long dummy ____cacheline_aligned = 0;
+ __delay_until_ul(cycles, &dummy, 0, 1);
}
EXPORT_SYMBOL(__delay);
-inline void __const_udelay(unsigned long xloops)
+void __const_udelay(unsigned long xloops)
{
__delay(xloops_to_cycles(xloops));
}
@@ -58,12 +88,12 @@ EXPORT_SYMBOL(__const_udelay);
void __udelay(unsigned long usecs)
{
- __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
+ __delay(USECS_TO_CYCLES(usecs));
}
EXPORT_SYMBOL(__udelay);
void __ndelay(unsigned long nsecs)
{
- __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
+ __delay(NSECS_TO_CYCLES(nsecs));
}
EXPORT_SYMBOL(__ndelay);
--
2.34.1
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