Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753431AbcLMB5e (ORCPT ); Mon, 12 Dec 2016 20:57:34 -0500 Received: from www.osadl.org ([62.245.132.105]:41390 "EHLO www.osadl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752913AbcLMB5d (ORCPT ); Mon, 12 Dec 2016 20:57:33 -0500 From: Nicholas Mc Guire To: Mauro Carvalho Chehab Cc: Sylwester Nawrocki , Laurent Pinchart , Sakari Ailus , Hans Verkuil , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Nicholas Mc Guire Subject: [PATCH RFC] [media] s5k6aa: set usleep_range greater 0 Date: Tue, 13 Dec 2016 02:58:02 +0100 Message-Id: <1481594282-12801-1-git-send-email-hofrat@osadl.org> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1715 Lines: 50 As this is not in atomic context and it does not seem like a critical timing setting a range of 1ms allows the timer subsystem to optimize the hrtimer here. Fixes: commit bfa8dd3a0524 ("[media] v4l: Add v4l2 subdev driver for S5K6AAFX sensor") Signed-off-by: Nicholas Mc Guire --- problem was located by coccinelle spatch The problem is that usleep_range is calculating the delay by exp = ktime_add_us(ktime_get(), min) delta = (u64)(max - min) * NSEC_PER_USEC so delta is set to 0 and then calls schedule_hrtimeout_range(exp, 0,...) effectively this means that the clock subsystem has no room to optimize which makes little sense as this is not atomic context anyway so there is not guaratee of precision here. As this is not a critical delay it is set to a range of 4 to 5 milliseconds - this change needs a review by someone that knows the details of the device though and preferably would increase that range. Patch was only compile tested with: x86_64_defconfig + MEDIA_SUPPORT=m MEDIA_CAMERA_SUPPORT=y (implies VIDEO_V4L2=m) MEDIA_DIGITAL_TV_SUPPORT=y, CONFIG_MEDIA_CONTROLLER=y, CONFIG_VIDEO_V4L2_SUBDEV_API=y Patch is against 4.9.0 (localversion-next is next-20161212) drivers/media/i2c/s5k6aa.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/media/i2c/s5k6aa.c b/drivers/media/i2c/s5k6aa.c index faee113..9fd254a 100644 --- a/drivers/media/i2c/s5k6aa.c +++ b/drivers/media/i2c/s5k6aa.c @@ -838,7 +838,7 @@ static int __s5k6aa_power_on(struct s5k6aa *s5k6aa) if (s5k6aa->s_power) ret = s5k6aa->s_power(1); - usleep_range(4000, 4000); + usleep_range(4000, 5000); if (s5k6aa_gpio_deassert(s5k6aa, RST)) msleep(20); -- 2.1.4