[PATCH 1/3] x86/tsc: Be consistent about use_tsc_delay()

From: Peter Zijlstra
Date: Fri Mar 04 2022 - 10:22:46 EST


Currently loops_per_jiffy is set in tsc_early_init(), but then don't
switch to delay_tsc, with the result that delay_loop is used with
loops_per_jiffy set for delay_tsc.

Then in (late) tsc_init() lpj_fine is set (which is mostly unused) and
after which use_tsc_delay() is finally called.

Move both loops_per_jiffy and use_tsc_delay() into
tsc_enable_sched_clock() which is called the moment tsc_khz is
determined, be it early or late. Keeping the lot consistent.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/kernel/tsc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1487,6 +1487,9 @@ static unsigned long __init get_loops_pe

static void __init tsc_enable_sched_clock(void)
{
+ loops_per_jiffy = get_loops_per_jiffy();
+ use_tsc_delay();
+
/* Sanitize TSC ADJUST before cyc2ns gets initialized */
tsc_store_and_check_tsc_adjust(true);
cyc2ns_init_boot_cpu();
@@ -1502,8 +1505,6 @@ void __init tsc_early_init(void)
return;
if (!determine_cpu_tsc_frequencies(true))
return;
- loops_per_jiffy = get_loops_per_jiffy();
-
tsc_enable_sched_clock();
}

@@ -1537,7 +1538,6 @@ void __init tsc_init(void)
enable_sched_clock_irqtime();

lpj_fine = get_loops_per_jiffy();
- use_tsc_delay();

check_system_tsc_reliable();