From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Stultz Subject: Re: [PATCH 1/5] Add functions producing system time given a backing counter value Date: Mon, 27 Jul 2015 20:44:06 -0700 Message-ID: References: <1438044416-15588-1-git-send-email-christopher.s.hall@intel.com> <1438044416-15588-2-git-send-email-christopher.s.hall@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Thomas Gleixner , Richard Cochran , Ingo Molnar , Jeff Kirsher , john.ronciak@intel.com, "H. Peter Anvin" , "x86@kernel.org" , lkml , netdev@vger.kernel.org To: Christopher Hall Return-path: In-Reply-To: <1438044416-15588-2-git-send-email-christopher.s.hall@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Jul 27, 2015 at 5:46 PM, Christopher Hall wrote: > * counter_to_rawmono64 > * counter_to_mono64 > * counter_to_realtime64 > > Enables drivers to translate a captured system clock counter to system > time. This is useful for network and audio devices that capture timestamps > in terms of both the system clock and device clock. Huh. So for counter_to_realtime64 & mono64, this seems to ignore the fact that the multiplier is constantly adjusted and corrected. So that calling the function twice with the same counter value may result in different returned values. I've not yet groked the whole patchset, but it seems like there needs to be some mechanism that ensures the counter value is captured and used in the same (or at least close) interval that the timekeeper data is valid for. thanks -john