linux-kernel - Re: [Y2038] [PATCH] drm/sti: Use 64-bit timestamps

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Date:	Mon, 18 Apr 2016 12:32:12 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	y2038@...ts.linaro.org
Cc:	Vincent ABRIOU <vincent.abriou@...com>,
	David Airlie <airlied@...ux.ie>,
	Benjamin Gaignard <benjamin.gaignard@...aro.org>,
	Tina Ruchandani <ruchandani.tina@...il.com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Y2038] [PATCH] drm/sti: Use 64-bit timestamps

On Monday 18 April 2016 12:02:35 Vincent ABRIOU wrote:
> 
> getrawmonotonic comes from a legacy code so the use is not intentional.
> Honestly, it is not clear to me the difference between monotonic and 
> rawmonotonic. But in the debug context in which it is used, ktime_get 
> and ktime_get_raw will deliver the same level of information we need. So 
> implementation done by Tina is fine for me.
> 

Ok, cool, thanks for confirming!

FWIW, the best way I can see for illustrating the difference is that
rawmonotonic time is for things that should be synchronized with the
machines clock generators (e.g. A/V sync), while monotonic time is
for the case where you want to synchronize with another machine (or
the internet) that may have a slightly different clock generator but
uses NTP to correct for that.

In most cases the difference is irrelevant and we tend to use monotonic
time by default.

	Arnd