From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Wahren Subject: Re: [PATCH] pwm: mxs: set pwm_chip can_sleep flag Date: Fri, 25 Apr 2014 16:11:11 +0200 Message-ID: <535A6CFF.2020800@i2se.com> References: <1396956597-26159-1-git-send-email-shawn.guo@freescale.com> <5343FDD3.3070308@i2se.com> <20140408175904.GT29751@pengutronix.de> <20140408234243.GB13898@piout.net> <20140409082341.GV29751@pengutronix.de> <20140409100313.GA20704@piout.net> <20140409104652.GC9527@ulmo> <20140409143516.GW29751@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mout.kundenserver.de ([212.227.126.130]:51856 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751593AbaDYOLo (ORCPT ); Fri, 25 Apr 2014 10:11:44 -0400 In-Reply-To: <20140409143516.GW29751@pengutronix.de> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: =?ISO-8859-1?Q?Uwe_Kleine-K=F6nig?= , Thierry Reding Cc: Alexandre Belloni , Shawn Guo , linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Hi, Am 09.04.2014 16:35, schrieb Uwe Kleine-K=F6nig: > Hello, > > On Wed, Apr 09, 2014 at 12:46:53PM +0200, Thierry Reding wrote: >> >> My preference would be simply d). Mostly because I don't like specia= l >> cases and especially because I don't see an advantage in special cas= ing >> 0 and full period duty cycles. That doesn't mean of course that driv= ers >> can't special case if they really want or have to. > Well d' is just an optimisation, because if you have a duty cycle > between 0 and full (exclusive) and no other means of syncronisation > you cannot influence where pwm_disable stops the output, at low or hi= gh. > > Do we have cases where pwm_disable makes the pin high-z? Or something > else which violates the assumption "pwm_config(pwm, 0, period); > pwm_disable(pwm); makes the pin 0"? > =20 >> That said I've also been thinking about adding support for e), which >> would allow atomically changing the duty cycle, period and polarity = of a >> channel. This might become necessary at some point. > On i.MX28 you cannot change atomically, only program atomically. The > current period will end regularily anyhow as programmed before. But > maybe that's what you mean?! > > Best regards > Uwe > i want to ask gently, if somebody working on this issue? Regards, Stefan Wahren