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x86/delay: Refactor delay_mwaitx() for TPAUSE support

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Refactor code to make it easier to add a new model specific function to
delay for a number of cycles.

No functional change.

Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Kyung Min Park <kyung.min.park@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/1587757076-30337-3-git-send-email-kyung.min.park@intel.com
This commit is contained in:
Kyung Min Park 2020-04-24 12:37:55 -07:00 committed by Thomas Gleixner
parent e882489024
commit 46f90c7aad
1 changed files with 30 additions and 18 deletions
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48
arch/x86/lib/delay.c
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@ -34,6 +34,7 @@ static void delay_loop(u64 __loops);
* during boot.
*/
static void (*delay_fn)(u64) __ro_after_init = delay_loop;
static void (*delay_halt_fn)(u64 start, u64 cycles) __ro_after_init;
/* simple loop based delay: */
static void delay_loop(u64 __loops)
@ -100,9 +101,33 @@ static void delay_tsc(u64 cycles)
* counts with TSC frequency. The input value is the number of TSC cycles
* to wait. MWAITX will also exit when the timer expires.
*/
static void delay_mwaitx(u64 cycles)
static void delay_halt_mwaitx(u64 unused, u64 cycles)
{
u64 start, end, delay;
u64 delay;
delay = min_t(u64, MWAITX_MAX_WAIT_CYCLES, cycles);
/*
* Use cpu_tss_rw as a cacheline-aligned, seldomly accessed per-cpu
* variable as the monitor target.
*/
__monitorx(raw_cpu_ptr(&cpu_tss_rw), 0, 0);
/*
* AMD, like Intel, supports the EAX hint and EAX=0xf means, do not
* enter any deep C-state and we use it here in delay() to minimize
* wakeup latency.
*/
__mwaitx(MWAITX_DISABLE_CSTATES, delay, MWAITX_ECX_TIMER_ENABLE);
}
/*
* Call a vendor specific function to delay for a given amount of time. Because
* these functions may return earlier than requested, check for actual elapsed
* time and call again until done.
*/
static void delay_halt(u64 __cycles)
{
u64 start, end, cycles = __cycles;
/*
* Timer value of 0 causes MWAITX to wait indefinitely, unless there
@ -114,21 +139,7 @@ static void delay_mwaitx(u64 cycles)
start = rdtsc_ordered();
for (;;) {
delay = min_t(u64, MWAITX_MAX_WAIT_CYCLES, cycles);
/*
* Use cpu_tss_rw as a cacheline-aligned, seldomly
* accessed per-cpu variable as the monitor target.
*/
__monitorx(raw_cpu_ptr(&cpu_tss_rw), 0, 0);
/*
* AMD, like Intel's MWAIT version, supports the EAX hint and
* EAX=0xf0 means, do not enter any deep C-state and we use it
* here in delay() to minimize wakeup latency.
*/
__mwaitx(MWAITX_DISABLE_CSTATES, delay, MWAITX_ECX_TIMER_ENABLE);
delay_halt_fn(start, cycles);
end = rdtsc_ordered();
if (cycles <= end - start)
@ -147,7 +158,8 @@ void __init use_tsc_delay(void)
void use_mwaitx_delay(void)
{
delay_fn = delay_mwaitx;
delay_halt_fn = delay_halt_mwaitx;
delay_fn = delay_halt;
}
int read_current_timer(unsigned long *timer_val)