x86/tsc: Calibrate tsc only once

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@linutronix.de>
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-20-pasha.tatashin@oracle.com

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 2701d221583a26071b16c1caf1d34b3de7c7b007..c4368ff73652ab4b01f162dbf59137fe2481a59d 100644 (file)
--- 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 7490de925a811f34f977faf5b0aff6007700230f..5d32c55aeb8bcddf1d3a55b521502c0ef554ec69 100644 (file)
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1014,6 +1014,7 @@ void __init setup_arch(char **cmdline_p)
         */
        init_hypervisor_platform();
 
+       tsc_early_init();
        x86_init.resources.probe_roms();
 
        /* after parse_early_param, so could debug it */
@@ -1199,7 +1200,6 @@ void __init setup_arch(char **cmdline_p)
 
        memblock_find_dma_reserve();
 
-       tsc_early_delay_calibrate();
        if (!early_xdbc_setup_hardware())
                early_xdbc_register_console();
 

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 186395041725ef4dcb69e11ce780e14f9c1811b8..4cab2236169e5118246b2beb939db173b12da65a 100644 (file)
--- 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 @@ unreg:
  */
 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 __init determine_cpu_tsc_frequencies(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 +1355,52 @@ 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 __init 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_frequencies())
+               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_frequencies()) {
+                       mark_tsc_unstable("could not calculate TSC khz");
+                       setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
+                       return;
+               }
        }
 
        /* Sanitize TSC ADJUST before cyc2ns gets initialized */
@@ -1413,10 +1423,7 @@ 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();