At 07/12/2018 08:04 AM, Pavel Tatashin wrote:
During boot tsc is calibrated twice: once in tsc_early_delay_calibrate(),
and the second time in tsc_init().
Rename tsc_early_delay_calibrate() to tsc_early_init(), and rework it so
the calibration is done only early, and make tsc_init() to use the values
already determined in tsc_early_init().
Sometimes it is not possible to determine tsc early, as the subsystem that
is required is not yet initialized, in such case try again later in
tsc_init().
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Hi Pavel,
Aha, a complex solution for a simple problem! ;-) And I did find any
benefits of doing that. did I miss something?
As the cpu_khz and tsc_khz are global variables and the tsc_khz may
be reset to cpu_khz. How about the following patch.
Thanks,
dou
------------------------8<-----------------------------------
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 74392d9d51e0..e54fa1037d45 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1370,8 +1370,10 @@ void __init tsc_init(void)
return;
}
- cpu_khz = x86_platform.calibrate_cpu();
- tsc_khz = x86_platform.calibrate_tsc();
+ if (!tsc_khz) {
+ cpu_khz = x86_platform.calibrate_cpu();
+ tsc_khz = x86_platform.calibrate_tsc();
+ }
/*
* Trust non-zero tsc_khz as authorative,
---
arch/x86/include/asm/tsc.h | 2 +-
arch/x86/kernel/setup.c | 2 +-
arch/x86/kernel/tsc.c | 86 ++++++++++++++++++++------------------
3 files changed, 48 insertions(+), 42 deletions(-)
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 2701d221583a..c4368ff73652 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -33,7 +33,7 @@ static inline cycles_t get_cycles(void)
extern struct system_counterval_t convert_art_to_tsc(u64 art);
extern struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns);
-extern void tsc_early_delay_calibrate(void);
+extern void tsc_early_init(void);
extern void tsc_init(void);
extern void mark_tsc_unstable(char *reason);
extern int unsynchronized_tsc(void);
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 01fcc8bf7c8f..07445482bb57 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1014,7 +1014,7 @@ void __init setup_arch(char **cmdline_p)
*/
init_hypervisor_platform();
- tsc_early_delay_calibrate();
+ tsc_early_init();
x86_init.resources.probe_roms();
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 186395041725..bc8eb82050a3 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -33,6 +33,8 @@ EXPORT_SYMBOL(cpu_khz);
unsigned int __read_mostly tsc_khz;
EXPORT_SYMBOL(tsc_khz);
+#define KHZ 1000
+
/*
* TSC can be unstable due to cpufreq or due to unsynced TSCs
*/
@@ -1335,34 +1337,10 @@ static int __init init_tsc_clocksource(void)
*/
device_initcall(init_tsc_clocksource);
-void __init tsc_early_delay_calibrate(void)
-{
- unsigned long lpj;
-
- if (!boot_cpu_has(X86_FEATURE_TSC))
- return;
-
- cpu_khz = x86_platform.calibrate_cpu();
- tsc_khz = x86_platform.calibrate_tsc();
-
- tsc_khz = tsc_khz ? : cpu_khz;
- if (!tsc_khz)
- return;
-
- lpj = tsc_khz * 1000;
- do_div(lpj, HZ);
- loops_per_jiffy = lpj;
-}
-
-void __init tsc_init(void)
+static bool determine_cpu_tsc_frequncies(void)
{
- u64 lpj, cyc;
- int cpu;
-
- if (!boot_cpu_has(X86_FEATURE_TSC)) {
- setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
- return;
- }
+ /* Make sure that cpu and tsc are not already calibrated */
+ WARN_ON(cpu_khz || tsc_khz);
cpu_khz = x86_platform.calibrate_cpu();
tsc_khz = x86_platform.calibrate_tsc();
@@ -1377,20 +1355,51 @@ void __init tsc_init(void)
else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
cpu_khz = tsc_khz;
- if (!tsc_khz) {
- mark_tsc_unstable("could not calculate TSC khz");
- setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
- return;
- }
+ if (tsc_khz == 0)
+ return false;
pr_info("Detected %lu.%03lu MHz processor\n",
- (unsigned long)cpu_khz / 1000,
- (unsigned long)cpu_khz % 1000);
+ (unsigned long)cpu_khz / KHZ,
+ (unsigned long)cpu_khz % KHZ);
if (cpu_khz != tsc_khz) {
pr_info("Detected %lu.%03lu MHz TSC",
- (unsigned long)tsc_khz / 1000,
- (unsigned long)tsc_khz % 1000);
+ (unsigned long)tsc_khz / KHZ,
+ (unsigned long)tsc_khz % KHZ);
+ }
+ return true;
+}
+
+static unsigned long get_loops_per_jiffy(void)
+{
+ unsigned long lpj = tsc_khz * KHZ;
+
+ do_div(lpj, HZ);
+ return lpj;
+}
+
+void __init tsc_early_init(void)
+{
+ if (!boot_cpu_has(X86_FEATURE_TSC))
+ return;
+ if (!determine_cpu_tsc_frequncies())
+ return;
+ loops_per_jiffy = get_loops_per_jiffy();
+}
+
+void __init tsc_init(void)
+{
+ if (!boot_cpu_has(X86_FEATURE_TSC)) {
+ setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
+ return;
+ }
+
+ if (!tsc_khz) {
+ /* We failed to determine frequencies earlier, try again */
+ if (!determine_cpu_tsc_frequncies()) {
+ mark_tsc_unstable("could not calculate TSC khz");
+ return;
+ }
}
/* Sanitize TSC ADJUST before cyc2ns gets initialized */
@@ -1413,10 +1422,7 @@ void __init tsc_init(void)
if (!no_sched_irq_time)
enable_sched_clock_irqtime();
- lpj = ((u64)tsc_khz * 1000);
- do_div(lpj, HZ);
- lpj_fine = lpj;
-
+ lpj_fine = get_loops_per_jiffy();
use_tsc_delay();
check_system_tsc_reliable();
--
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