From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Stultz Subject: Re: [PATCH] Round the calculated scale factor in set_cyc2ns_scale() Date: Wed, 19 Dec 2012 10:28:29 -0800 Message-ID: <50D2074D.4000101@linaro.org> References: <1354717009-2687-1-git-send-email-berndfaust@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org To: Bernd Faust Return-path: In-Reply-To: <1354717009-2687-1-git-send-email-berndfaust@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On 12/05/2012 06:16 AM, Bernd Faust wrote: > During some experiments with an external clock (in a FPGA), we saw that > the TSC clock drifted approx. 2.5ms per second. > > This drift was caused by the current way of calculating the scale. > In our case cpu_khz had a value of 3292725. This resulted in a scale > value of 310. But when doing the calculation by hand it shows that the > actual value is 310.9886188491, so a value of 311 would be more precise. > > With this change the value is rounded. > > Signed-off-by: Bernd Faust Thanks for sending this in! I've queued it, but because I was slow here, it will have to wait for 3.9. Sorry for the delay, and thanks again! -john