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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 BEA05C5DF61 for ; Thu, 7 Nov 2019 06:51:30 +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 8EB5921882 for ; Thu, 7 Nov 2019 06:51:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="rRdO/X8O" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8EB5921882 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=wDUeWnA8bY9FncJGYfCwAge1VzZTL3EmyuiW3+++lZM=; b=rRdO/X8OrkW5FF ATlOsup05n6SpNvDLbGTG4PoCI/pLmqtAQxNqDLSmSvFXOLZiM5iAypcleFYiphC5P7z4fG8Tv6Fs +Rk3haPdI6Q8Eiv4oOmfQUIkWbDp8iBEFGlOGMHAZ2TpI52X/l0lDNQ9fWNWGL0iaDzE3iDP9/+KS pIzqHtS72lb4usCm4YTSZsQszqVfzbuxltbKzx6VW0mdaDTH3EW9SObjU5g/8jFewU7s2G9xlCUfE UdQ+YQ3vdqS7podHJ8orYFh9cEMVccyFcNLSI5Q89NSfzCCD5g+iDAw8rm/5TP7fDWeF5gOKeNA2u 76wykV7GCpsznySZ3aTQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iSbdh-0000mq-U1; Thu, 07 Nov 2019 06:51:29 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iSbdf-0000mA-2q for linux-arm-kernel@lists.infradead.org; Thu, 07 Nov 2019 06:51:28 +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 1iSbdX-0001kX-O4; Thu, 07 Nov 2019 07:51:19 +0100 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1iSbdW-0007qU-3c; Thu, 07 Nov 2019 07:51:18 +0100 Date: Thu, 7 Nov 2019 07:51:18 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: =?iso-8859-1?Q?Cl=E9ment_P=E9ron?= Subject: Re: [PATCH v3 4/7] pwm: sun4i: Add support to output source clock directly Message-ID: <20191107065118.j4s5cghj4ark7sql@pengutronix.de> References: <20191105131456.32400-1-peron.clem@gmail.com> <20191105131456.32400-5-peron.clem@gmail.com> <20191105145659.ffezqntodsys4phn@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-20191106_225127_124203_60FCB8C5 X-CRM114-Status: GOOD ( 13.48 ) 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: Mark Rutland , linux-pwm@vger.kernel.org, Jernej Skrabec , devicetree , linux-kernel , Maxime Ripard , Rob Herring , Chen-Yu Tsai , Thierry Reding , Philipp Zabel , linux-arm-kernel 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 Hello Cl=E9ment, On Wed, Nov 06, 2019 at 10:24:39PM +0100, Cl=E9ment P=E9ron wrote: > On Tue, 5 Nov 2019 at 15:57, Uwe Kleine-K=F6nig > wrote: > > On Tue, Nov 05, 2019 at 02:14:53PM +0100, Cl=E9ment P=E9ron wrote: > > > + bypass =3D state->enabled && > > > + (state->period * clk_rate >=3D NSEC_PER_SEC) && > > > > This is too coarse. With state->period =3D 1000000 this is fulfilled > > (unless the multiplication overflows). > = > Sorry, misunderstood the previous mail > = > What about something like this ? > ((state->period - 1) * clk_rate <=3D NSEC_PER_SEC) && > ((state->period + 1) * clk_rate >=3D NSEC_PER_SEC) && > ((state->duty_cycle - 1) * 2 <=3D state->period) && > ((state->duty_cycle + 1) * 2 >=3D state->period); > = > We are sure that the user is looking for a PWM around the OSC with a > 50% duty cycle ? This again is too strict. The general policy to fulfill a request is: 1) provide the longest possible period not bigger than requested 2) provide the longest possible duty cycle not bigger than requested 3) if possible complete the currently running period before switching and don't return to the user before the new setting is active. Document the behaviour prominently because the code (usually) doesn't allow to understand the hardware's features here. 4) A disabled PWM should output the inactive level And then there is a corner case: If the user requests .duty_cycle =3D 0, .enabled =3D 1 it is ok to provide .enabled =3D 0 iff otherwise 0% isn't possible. So the right check for bypass is: state->period * clk_rate >=3D NSEC_PER_SEC && state->period * clk_rate < whatevercanbereachedwithoutbypass && state->duty_cycle * clk_rate * 2 >=3D NSEC_PER_SEC 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