Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751058AbaFLWyS (ORCPT ); Thu, 12 Jun 2014 18:54:18 -0400 Received: from mail-oa0-f48.google.com ([209.85.219.48]:49557 "EHLO mail-oa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750773AbaFLWyR (ORCPT ); Thu, 12 Jun 2014 18:54:17 -0400 MIME-Version: 1.0 In-Reply-To: <1402603992-12466-2-git-send-email-davidriley@chromium.org> References: <1402603992-12466-1-git-send-email-davidriley@chromium.org> <1402603992-12466-2-git-send-email-davidriley@chromium.org> Date: Thu, 12 Jun 2014 15:54:16 -0700 X-Google-Sender-Auth: vDOKnv7Ixr3cHtVM7cSl5u9cH6w Message-ID: Subject: Re: [PATCH v3 1/2] kernel: time: Add udelay_test module to validate udelay From: Doug Anderson To: David Riley Cc: Thomas Gleixner , John Stultz , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David, On Thu, Jun 12, 2014 at 1:13 PM, David Riley wrote: > Create a module that allows udelay() to be executed to ensure that > it is delaying at least as long as requested (with a little bit of > error allowed). > > There are some configurations which don't have reliably udelay > due to using a loop delay with cpufreq changes which should use > a counter time based delay instead. This test aims to identify > those configurations where timing is unreliable. > > Signed-off-by: David Riley > --- > kernel/time/Kconfig | 7 ++ > kernel/time/Makefile | 1 + > kernel/time/udelay_test.c | 170 ++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 178 insertions(+) Looks good to me. Also properly demonstrates that utter brokenness that is udelay on exynos5420 and exynos5800 right now upstream, like: 171 usecs x 100: exp=171000 allowed=170145 min=57791 avg=61586 max=435750 FAIL=99 ...the same kernel on exynos5250 shows all passes (though I didn't stress the low speeds where there are known problems due to the intermediate freq transition). Reviewed-by: Doug Anderson Tested-by: Doug Anderson -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/