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 D652FC3A59E for ; Mon, 2 Sep 2019 20:06:47 +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 A8FB4214AE for ; Mon, 2 Sep 2019 20:06:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="CekrI4Qy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A8FB4214AE 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=bbfYgJ+wrQbwww1LN5B4evm5nfHJ6Lre3kIpKI41CBg=; b=CekrI4QyYs57rv WlrcxVPg/zEiHcV4r45qyicdIVlgnZDPSjm1Tve/1EGfqumEzNY+kU4KUSti/jUzKCfWx7a72Rza7 acF1WRdGrd5c6Pefd34ntlGWVgp3gXlMRBxZyhryMZAfcMB/LrotMSlwDa/6CnhKYH5kWB61gj0JD 202rYj8WVuLLt4kliI1w+Q2XxQLfcXjB7QRvg3Tnd7MzUZayrWkZuZqFPzVLquPbaoR5PLYBvrxEN 3oixL/B0FWEzsVWy6jUsb2imDXjC2y1gJDL9BkeRHHFVaZLf6RkvRUscbXWo+aQF+en1MCWn3KZmJ 8E01BrG+6KdOVLD/cLIw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i4sai-0006w7-26; Mon, 02 Sep 2019 20:06:20 +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 (Red Hat Linux)) id 1i4sae-0006vj-IC for linux-arm-kernel@lists.infradead.org; Mon, 02 Sep 2019 20:06:18 +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 1i4saY-000596-5w; Mon, 02 Sep 2019 22:06:10 +0200 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1i4saT-0002Nc-Kv; Mon, 02 Sep 2019 22:06:05 +0200 Date: Mon, 2 Sep 2019 22:06:05 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Claudiu.Beznea@microchip.com Subject: Re: [PATCH v2 6/6] pwm: atmel: implement .get_state() Message-ID: <20190902200605.2tipkzh3n7ylehku@pengutronix.de> References: <20190824001041.11007-1-uwe@kleine-koenig.org> <20190824001041.11007-7-uwe@kleine-koenig.org> <8da4ef26-872f-beaf-b5cb-9d8cb93a2ce9@microchip.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <8da4ef26-872f-beaf-b5cb-9d8cb93a2ce9@microchip.com> 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-20190902_130616_602801_FBB35987 X-CRM114-Status: GOOD ( 18.85 ) 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: linux-pwm@vger.kernel.org, alexandre.belloni@bootlin.com, Ludovic.Desroches@microchip.com, thierry.reding@gmail.com, 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 Hello Claudiu, On Wed, Aug 28, 2019 at 10:26:18AM +0000, Claudiu.Beznea@microchip.com wrot= e: > On 24.08.2019 03:10, Uwe Kleine-K=F6nig wrote: > > External E-Mail > > This function reads back the configured parameters from the hardware. As > > .apply rounds down (mostly) I'm rounding up in .get_state() to achieve > > that applying a state just read from hardware is a no-op. > = > Since this read is only at probing, at least for the moment, and, as far = as Yes, up to now .get_state() is only called at probing time. There is a patch series (by me) on the list that changes that. (Though I'm not entirely sure this is a good idea. Will comment my doubts in that thread later.) > I remember, the idea w/ .get_state was to reflect in Linux the states of > PWMs that were setup before Linux takes control (e.g. PWMs setup in > bootloaders) I think it would no problem if it would be no-ops in this > scenario. IMHO it should be a no-op. > In case of run-time state retrieval, pwm_get_state() should be > enough. If one would get the state previously saved w/ this .get_state API > he/she would change it, then it would apply the changes to the hardware. = No > changes of PWM state would be anyway skipped from the beginning, in > pwm_apply_state() by this code: > = > if (state->period =3D=3D pwm->state.period && > state->duty_cycle =3D=3D pwm->state.duty_cycle && > state->polarity =3D=3D pwm->state.polarity && > state->enabled =3D=3D pwm->state.enabled) > return 0; > = > But maybe I'm missing something. There is a problem I want to solve generally, not only for the atmel driver. For example I consider it "expected" that s1 =3D pwm_get_state(pwm) pwm_apply_state(pwm, s2) pwm_apply_state(pwm, s1) ends in the same configuration as it started. For that it is necessary (even for the atmel driver with the guard you pointed out above) to round up in .get_state if .apply rounds down. 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