From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C1E6C43331 for ; Mon, 30 Mar 2020 16:07:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A7722072E for ; Mon, 30 Mar 2020 16:07:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=pqgruber.com header.i=@pqgruber.com header.b="QYhulaBI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728579AbgC3QHr (ORCPT ); Mon, 30 Mar 2020 12:07:47 -0400 Received: from mail.pqgruber.com ([52.59.78.55]:57710 "EHLO mail.pqgruber.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726017AbgC3QHr (ORCPT ); Mon, 30 Mar 2020 12:07:47 -0400 Received: from workstation.tuxnet (213-47-165-233.cable.dynamic.surfer.at [213.47.165.233]) by mail.pqgruber.com (Postfix) with ESMTPSA id 750DEC72753; Mon, 30 Mar 2020 18:07:45 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pqgruber.com; s=mail; t=1585584465; bh=q0R/eIdBiL04ZzaNH27/H9PSTVwoRPsiin/dQgKMXBI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QYhulaBINJV3XGmYtogjp34DSdxijcK/aLu0zp+G4renddGunWyY89jKOksGTJZWL gE5/ejFEhNBXZuJmH2ZkNp7K+3nuOg9WCutaXNF1w0Zd1RM80UYeo2IVHjwtjg421F Zit/gN3vCO1IE9Lb9eyCA8vxQB0dRWx2JBSSm9WI= Date: Mon, 30 Mar 2020 18:07:44 +0200 From: Clemens Gruber To: Thierry Reding Cc: Matthias Schiffer , u.kleine-koenig@pengutronix.de, linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, andy.shevchenko@gmail.com Subject: Re: [PATCH 2/4] pwm: pca9685: remove ALL_LED PWM channel Message-ID: <20200330160744.GA777@workstation.tuxnet> References: <20200226135229.24929-1-matthias.schiffer@ew.tq-group.com> <20200226135229.24929-2-matthias.schiffer@ew.tq-group.com> <20200330130757.GC2431644@ulmo> <20200330133450.GA1530@workstation.tuxnet> <20200330154036.GB2817345@ulmo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200330154036.GB2817345@ulmo> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 30, 2020 at 05:40:36PM +0200, Thierry Reding wrote: > On Mon, Mar 30, 2020 at 03:34:50PM +0200, Clemens Gruber wrote: > > Hi, > > > > On Mon, Mar 30, 2020 at 03:07:57PM +0200, Thierry Reding wrote: > > > On Wed, Feb 26, 2020 at 02:52:27PM +0100, Matthias Schiffer wrote: > > > > The interaction of the ALL_LED PWM channel with the other channels was > > > > not well-defined. As the ALL_LED feature does not seem very useful and > > > > it was making the code significantly more complex, simply remove it. > > > > > > > > Signed-off-by: Matthias Schiffer > > > > --- > > > > drivers/pwm/pwm-pca9685.c | 115 ++++++-------------------------------- > > > > 1 file changed, 17 insertions(+), 98 deletions(-) > > > > > > Applied, thanks. > > > > > > Thierry > > > > I was not reading the mailing list in the last weeks, so I only saw the > > patch today. > > > > We are using the ALL_LED channel in production to reduce the delay when > > all 16 PWM outputs need to be set to the same duty cycle. > > > > I am not sure it is a good idea to remove this feature. > > Can you specify what platform this is and where the code is that does > this. I can't really find any device tree users of this and I don't know > if there's a good way to find out what other users there are, but this > isn't the first time this driver has created confusion, so please help > collect some more information about it's use so we can avoid this in the > future. The platform is ARM, it's a custom board with an NXP i.MX6. The device tree is not upstreamed. As there are multiple companies involved in changes to this driver, I assume that it is in use, even though there are no in-tree users. Also: As you can set the ALL channel from userspace, it will be very difficult to find out how often the ALL feature is being used somewhere. > > I'll back out this particular patch since you're using it. Can you give > the other three patches a try to see if they work for you? Thanks! I saw your other mail. Patch 1 looks good to me. I will look at the new version of patches 3 and 4 and test them when they appear on the list. Clemens