linux-kernel - [PATCH v2 1/3] powerpc/time: Export boot

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Message-ID: <20250204063948.643852-1-kjain@linux.ibm.com>
Date: Tue,  4 Feb 2025 12:09:46 +0530
From: Kajol Jain <kjain@...ux.ibm.com>
To: maddy@...ux.ibm.com
Cc: atrajeev@...ux.vnet.ibm.com, kjain@...ux.ibm.com, disgoel@...ux.ibm.com,
        hbathini@...ux.ibm.com, adubey@...ux.ibm.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        aboorvad@...ux.ibm.com
Subject: [PATCH v2 1/3] powerpc/time: Export boot_tb and log initial timebase at boot

From: Aboorva Devarajan <aboorvad@...ux.ibm.com>

- Export `boot_tb` for external use, this is useful in perf vpa-dtl
  interface, where `boot_tb` can be used to convert raw timebase
  values to it's relative boot timestamp.

- Log the initial timebase at `time_init` as it is a useful
  information which can be referred to as needed.

Signed-off-by: Aboorva Devarajan <aboorvad@...ux.ibm.com>
Signed-off-by: Kajol Jain <kjain@...ux.ibm.com>
---
 arch/powerpc/include/asm/time.h | 1 +
 arch/powerpc/kernel/time.c      | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index 9bdd8080299b..b6fc5df01d53 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h
@@ -23,6 +23,7 @@ extern u64 decrementer_max;
 extern unsigned long tb_ticks_per_jiffy;
 extern unsigned long tb_ticks_per_usec;
 extern unsigned long tb_ticks_per_sec;
+extern u64 boot_tb;
 extern struct clock_event_device decrementer_clockevent;
 extern u64 decrementer_max;
 
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 0727332ad86f..6e8548f0e48f 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -137,7 +137,8 @@ EXPORT_SYMBOL_GPL(rtc_lock);
 
 static u64 tb_to_ns_scale __read_mostly;
 static unsigned tb_to_ns_shift __read_mostly;
-static u64 boot_tb __read_mostly;
+u64 boot_tb __read_mostly;
+EXPORT_SYMBOL_GPL(boot_tb);
 
 extern struct timezone sys_tz;
 static long timezone_offset;
@@ -943,6 +944,7 @@ void __init time_init(void)
 	tb_to_ns_shift = shift;
 	/* Save the current timebase to pretty up CONFIG_PRINTK_TIME */
 	boot_tb = get_tb();
+	pr_debug("%s: timebase at boot: %llu\n", __func__, (unsigned long long)boot_tb);
 
 	/* If platform provided a timezone (pmac), we correct the time */
 	if (timezone_offset) {
-- 
2.43.0