linux-kernel - Re: [PATCH 2/3] ntp: add ADJ

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Message-ID: <AANLkTi=LqkC-tKzbb6y=iL0UvFYcfcHSuX=jVVFCk1uR@mail.gmail.com>
Date:	Wed, 29 Dec 2010 05:47:19 +0900
From:	"Kuwahara,T." <6vvetjsrt26xsrzlh1z0zn4d2grdah@...il.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	linux-kernel@...r.kernel.org,
	Richard Cochran <richardcochran@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Cochran <richard.cochran@...cron.at>
Subject: Re: [PATCH 2/3] ntp: add ADJ_SETOFFSET mode bit

On Tue, Dec 28, 2010 at 8:40 AM, John Stultz <john.stultz@...aro.org> wrote:
> From: Richard Cochran <richardcochran@...il.com>
>
> This patch adds a new mode bit into the timex structure. When set, the
> bit instructs the kernel to add the given time value to the current time.

I came up with this simple solution: "Just use ADJ_OFFSET as usual,
but don't forget to disable the kernel PLL."

Here's my (untested) patch.

---
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index c631168..d492887 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -119,14 +119,21 @@
 	return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 }

-static void ntp_update_offset(long offset)
+static void ntp_update_offset(long offset, struct timespec *ts)
 {
 	s64 freq_adj;
 	s64 offset64;
 	long secs;

-	if (!(time_status & STA_PLL))
+	if (!(time_status & STA_PLL)) {
+		offset64 = (s64)offset;
+		if (!(time_status & STA_NANO))
+			offset64 *= NSEC_PER_USEC;
+
+		set_normalized_timespec(ts, ts->tv_sec, offset64 + ts->tv_nsec);
+
 		return;
+	}

 	if (!(time_status & STA_NANO))
 		offset *= NSEC_PER_USEC;
@@ -430,7 +437,7 @@
 		time_tai = txc->constant;

 	if (txc->modes & ADJ_OFFSET)
-		ntp_update_offset(txc->offset);
+		ntp_update_offset(txc->offset, ts);

 	if (txc->modes & ADJ_TICK)
 		tick_usec = txc->tick;
@@ -526,6 +533,9 @@

 	write_sequnlock_irq(&xtime_lock);

+	if ((txc->modes & ADJ_OFFSET) && !(time_status & STA_PLL))
+		do_settimeofday(&ts);
+
 	txc->time.tv_sec = ts.tv_sec;
 	txc->time.tv_usec = ts.tv_nsec;
 	if (!(time_status & STA_NANO))
--
--
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