Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752107AbaKZFvq (ORCPT ); Wed, 26 Nov 2014 00:51:46 -0500 Received: from mail-ob0-f169.google.com ([209.85.214.169]:62286 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751231AbaKZFvo (ORCPT ); Wed, 26 Nov 2014 00:51:44 -0500 MIME-Version: 1.0 In-Reply-To: <1416944441-12066-2-git-send-email-sbranden@broadcom.com> References: <1416944441-12066-1-git-send-email-sbranden@broadcom.com> <1416944441-12066-2-git-send-email-sbranden@broadcom.com> Date: Tue, 25 Nov 2014 21:51:43 -0800 Message-ID: Subject: Re: [PATCH v2 1/4] pwm: kona: Remove setting default smooth type and polarity for all channels From: Tim Kryger To: Scott Branden Cc: Thierry Reding , Ray Jui , Arun Ramamurthy , bcm-kernel-feedback-list@broadcom.com, linux-pwm@vger.kernel.org, Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 25, 2014 at 11:40 AM, Scott Branden wrote: > From: Arun Ramamurthy > > The probe routine unnecessarily sets the smooth type and polarity for > all channels. This causes the channel for the speaker to click at the same > time the backlight turns on. The smooth type and polarity should be set individually > for each channel as required and no defaults need to be set. I am guessing you are talking about a PWM controlled beeper/buzzer. Can you mention what board you are observing this issue on? Also please explain why setting these bits result in an audible click. > > Signed-off-by: Arun Ramamurthy > Reviewed-by: Ray Jui > Signed-off-by: Scott Branden > --- > drivers/pwm/pwm-bcm-kona.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c > index 02bc048..29eef9e 100644 > --- a/drivers/pwm/pwm-bcm-kona.c > +++ b/drivers/pwm/pwm-bcm-kona.c > @@ -266,12 +266,9 @@ static int kona_pwmc_probe(struct platform_device *pdev) > return ret; > } > > - /* Set smooth mode, push/pull, and normal polarity for all channels */ > - for (chan = 0; chan < kp->chip.npwm; chan++) { > - value |= (1 << PWM_CONTROL_SMOOTH_SHIFT(chan)); > + /* Set push/pull for all channels */ > + for (chan = 0; chan < kp->chip.npwm; chan++) > value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan)); > - value |= (1 << PWM_CONTROL_POLARITY_SHIFT(chan)); > - } > > writel(value, kp->base + PWM_CONTROL_OFFSET); While the smooth bit need not be set here, it is important that the polarity bit be set. Otherwise software will report the polarity as normal when it it is actually inversed. Consider the case where a userspace process is controlling the PWM via sysfs. -- 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/