From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH 2/3] leds/pwm: Don't disable pwm when setting brightness to 0 Date: Thu, 5 Dec 2013 22:26:41 +0100 Message-ID: <20131205212641.GC4707@pengutronix.de> References: <1385412225-29740-1-git-send-email-u.kleine-koenig@pengutronix.de> <1385412225-29740-3-git-send-email-u.kleine-koenig@pengutronix.de> <20131202123318.GC12793@ulmo.nvidia.com> <20131202131807.GC29721@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from metis.ext.pengutronix.de ([92.198.50.35]:40874 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877Ab3LEV0r (ORCPT ); Thu, 5 Dec 2013 16:26:47 -0500 Content-Disposition: inline In-Reply-To: <20131202131807.GC29721@pengutronix.de> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Thierry Reding Cc: Bryan Wu , Richard Purdie , linux-leds@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kernel@pengutronix.de, Shawn Guo , Matt Sealey Hello Thierry, On Mon, Dec 02, 2013 at 02:18:07PM +0100, Uwe Kleine-K=F6nig wrote: > On Mon, Dec 02, 2013 at 01:33:19PM +0100, Thierry Reding wrote: > > On Mon, Nov 25, 2013 at 09:43:44PM +0100, Uwe Kleine-K=F6nig wrote: > > > This fixes disabling the LED on i.MX28. The PWM hardware delays u= sing > > > the newly set pwm-config until the beginning of a new period. It'= s very > > > likely that pwm_disable is called before the current period ends.= In > > > case the LED was on brightness=3Dmax before the LED stays on beca= use in > > > the disabled PWM block the period never ends. > > >=20 > > > Also only call pwm_enable only once in the probe call back and th= e > > > matching pwm_disable in .remove(). Moreover the pwm is explicitly > > > initialized to off. > >=20 > > While I do understand the reasoning behind this, if this is really = the > > behaviour that we need then there's no use in having pwm_enable() a= nd > > pwm_disable() at all. They can just be folded into pwm_get() and > > pwm_put(), respectively. > So after the first pwm_get the pwm starts with an unspecified duty > cycle? That's not that nice, is it? How can we come forward here? After all it's a real bug being fixed. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= |