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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 62363C3A5A6 for ; Mon, 23 Sep 2019 08:54:30 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 354A220820 for ; Mon, 23 Sep 2019 08:54:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="KbCo9Wx6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 354A220820 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Kp4901rR1d/pQ63YtVv+vim3aDHDto4+jVMBXpDZnvE=; b=KbCo9Wx6FE2kFf 7gFsmU17yyhnmH+JJpJJEViCo1vPaPIpA9PMqg3GjHEi9PBzfhNRwN1B5nRlhxGUfD8g6OXAXgKEh Aw3JUf5non1r0DOAk1jLYtK1Pt77OrVEfOioy6HiAnmCKMh03H3U3zQmVhiydQmFTsLo+SOQN+YWY 9hF7HfztJ14KBaq0e9/EpK1XJYPkWGiKLK0QKr9zlQftczmfNQ9oWUZjVyDDxIkdybNUCEYwbhFF8 gFkdbqbM+2qAXK+FaInfTCRcZvcXy4pI6xU+RoDYV9ZZ13IT5AU9pjAZ9T90A5Xt/Xck7Tkz8u1M6 3frMz+R2jCu06HD/sJIA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iCK6z-0007Pl-H9; Mon, 23 Sep 2019 08:54:25 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iCK6w-0007O3-84 for linux-arm-kernel@lists.infradead.org; Mon, 23 Sep 2019 08:54:23 +0000 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1iCK6p-0002FR-FW; Mon, 23 Sep 2019 10:54:15 +0200 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1iCK6o-0000rV-MN; Mon, 23 Sep 2019 10:54:14 +0200 Date: Mon, 23 Sep 2019 10:54:14 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Rasmus Villemoes Subject: Re: [PATCH 3/4] pwm: mxs: add support for inverse polarity Message-ID: <20190923085414.6d3gbby6gglpjsfe@pengutronix.de> References: <20190923081348.6843-1-linux@rasmusvillemoes.dk> <20190923081348.6843-4-linux@rasmusvillemoes.dk> <20190923082735.tzxyhvjlnztsxhsc@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190923_015422_314773_A9843A06 X-CRM114-Status: GOOD ( 17.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, Fabio Estevam , Sascha Hauer , linux-kernel@vger.kernel.org, Rob Herring , Thierry Reding , NXP Linux Team , Pengutronix Kernel Team , Shawn Guo , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 23, 2019 at 10:45:56AM +0200, Rasmus Villemoes wrote: > On 23/09/2019 10.27, Uwe Kleine-K=F6nig wrote: > > On Mon, Sep 23, 2019 at 10:13:47AM +0200, Rasmus Villemoes wrote: > >> > >> = > >> + pol_bits =3D state->polarity =3D=3D PWM_POLARITY_NORMAL ? > >> + PERIOD_POLARITY_NORMAL : PERIOD_POLARITY_INVERSE; > >> + > >> writel(duty_cycles << 16, > >> mxs->base + PWM_ACTIVE0 + pwm->hwpwm * 0x20); > >> - writel(PERIOD_PERIOD(period_cycles) | PERIOD_POLARITY_NORMAL | PERIO= D_CDIV(div), > >> + writel(PERIOD_PERIOD(period_cycles) | pol_bits | PERIOD_CDIV(div), > > = > > When will this affect the output? Only on the next start of a period, or > > immediatly? Can it happen that this results in a mixed output (i.e. a > > period that has already the new duty cycle from the line above but not > > the new polarity (or period)? > = > The data sheet says "Also, when the user reprograms the channel in this > manner, the new register values will not take effect until the beginning > of a new output period. This eliminates the potential for output > glitches that could occur if the registers were updated while the > channel was enabled and in the middle of a cycle.". So I think this > should be ok. "this manner" refers to the registers being written in the > proper order (first ACTIVEn, then PERIODn). OK. IMHO this is worth a code comment. Best regards Uwe -- = Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | http://www.pengutronix.de/ | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel