Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755176Ab2KHJw2 (ORCPT ); Thu, 8 Nov 2012 04:52:28 -0500 Received: from antcom.de ([188.40.178.216]:53633 "EHLO chuck.antcom.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755142Ab2KHJw0 (ORCPT ); Thu, 8 Nov 2012 04:52:26 -0500 Message-ID: <509B80A7.1060700@antcom.de> Date: Thu, 08 Nov 2012 10:51:35 +0100 From: Roland Stigge Organization: ANTCOM Open Source Research and Development User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.10) Gecko/20121027 Icedove/10.0.10 MIME-Version: 1.0 To: Alban Bedel CC: Thierry Reding , LKML , Alexandre Pereira da Silva Subject: Re: [PATCH] pwm: lpc32xx - Fix the PWM polarity References: <20121106181939.61c50233@avionic-0020.adnet.avionic-design.de> <1352301955-15960-1-git-send-email-alban.bedel@avionic-design.de> In-Reply-To: <1352301955-15960-1-git-send-email-alban.bedel@avionic-design.de> X-Enigmail-Version: 1.4.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1379 Lines: 49 On 07/11/12 16:25, Alban Bedel wrote: > Signed-off-by: Alban Bedel > --- > drivers/pwm/pwm-lpc32xx.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/drivers/pwm/pwm-lpc32xx.c b/drivers/pwm/pwm-lpc32xx.c > index adb87f0..0dc278d 100644 > --- a/drivers/pwm/pwm-lpc32xx.c > +++ b/drivers/pwm/pwm-lpc32xx.c > @@ -51,7 +51,11 @@ static int lpc32xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > c = 256 * duty_ns; > do_div(c, period_ns); > - duty_cycles = c; > + if (c == 0) > + c = 256; > + if (c > 255) > + c = 255; > + duty_cycles = 256 - c; Except for the range check (for the original c > 255), this results in: duty_cycles = 256 - c except for (c == 0) where duty_cycles = 1 which actually is duty_cycles = (256 - c) - 255 (think with the original c) i.e. nearly a polarity inversion in the case of (c == 0). Why is the case (c == 0) so special here? Maybe you can document this, if it is really intended? > > writel(PWM_ENABLE | PWM_RELOADV(period_cycles) | PWM_DUTY(duty_cycles), > lpc32xx->base + (pwm->hwpwm << 2)); -- 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/