From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758219AbaJ3HGN (ORCPT ); Thu, 30 Oct 2014 03:06:13 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59378 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752732AbaJ3HGM (ORCPT ); Thu, 30 Oct 2014 03:06:12 -0400 Date: Thu, 30 Oct 2014 08:06:10 +0100 Message-ID: From: Takashi Iwai To: Tina Ruchandani Cc: arnd@arndb.de, perex@perex.cz, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ALSA: es1968: Replace timeval with ktime_t In-Reply-To: <20141029174810.GA48058@localhost> References: <20141029174810.GA48058@localhost> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At Wed, 29 Oct 2014 10:48:10 -0700, Tina Ruchandani wrote: > > es1968_measure_clock uses struct timeval, which on 32-bit systems will overflow > in 2038, leading to incorrect interpretation of time.This patch changes the > function to use ktime_t instead of struct timeval, which implies: > - no y2038: ktime_t uses a 64-bit datatype explicitly. > - efficent subtraction: The earlier version computes the difference in usecs > while dealing with secs and nsecs. It requires checks to see if the nsecs of > stop is less than start. This patch uses a direct subtract of ktime_t and > converts to usecs. > - use of monotonic clock (ktime_get) over real time (do_gettimeofday), > which simplifies timekeeping, as it does not have to deal with cases > where stop_time is less than start_time. > > Signed-off-by: Tina Ruchandani > Reviewed-by: Arnd Bergmann Applied, thanks. Takashi > --- > sound/pci/es1968.c | 15 ++++++--------- > 1 file changed, 6 insertions(+), 9 deletions(-) > > diff --git a/sound/pci/es1968.c b/sound/pci/es1968.c > index a9956a7..6039700 100644 > --- a/sound/pci/es1968.c > +++ b/sound/pci/es1968.c > @@ -1710,7 +1710,8 @@ static void es1968_measure_clock(struct es1968 *chip) > int i, apu; > unsigned int pa, offset, t; > struct esm_memory *memory; > - struct timeval start_time, stop_time; > + ktime_t start_time, stop_time; > + ktime_t diff; > > if (chip->clock == 0) > chip->clock = 48000; /* default clock value */ > @@ -1761,12 +1762,12 @@ static void es1968_measure_clock(struct es1968 *chip) > snd_es1968_bob_inc(chip, ESM_BOB_FREQ); > __apu_set_register(chip, apu, 5, pa & 0xffff); > snd_es1968_trigger_apu(chip, apu, ESM_APU_16BITLINEAR); > - do_gettimeofday(&start_time); > + start_time = ktime_get(); > spin_unlock_irq(&chip->reg_lock); > msleep(50); > spin_lock_irq(&chip->reg_lock); > offset = __apu_get_register(chip, apu, 5); > - do_gettimeofday(&stop_time); > + stop_time = ktime_get(); > snd_es1968_trigger_apu(chip, apu, 0); /* stop */ > snd_es1968_bob_dec(chip); > chip->in_measurement = 0; > @@ -1777,12 +1778,8 @@ static void es1968_measure_clock(struct es1968 *chip) > offset &= 0xfffe; > offset += chip->measure_count * (CLOCK_MEASURE_BUFSIZE/2); > > - t = stop_time.tv_sec - start_time.tv_sec; > - t *= 1000000; > - if (stop_time.tv_usec < start_time.tv_usec) > - t -= start_time.tv_usec - stop_time.tv_usec; > - else > - t += stop_time.tv_usec - start_time.tv_usec; > + diff = ktime_sub(stop_time, start_time); > + t = ktime_to_us(diff); > if (t == 0) { > dev_err(chip->card->dev, "?? calculation error..\n"); > } else { > -- > 2.1.0.rc2.206.gedb03e5 >