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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 9226BC12002 for ; Fri, 16 Jul 2021 07:10:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7907E611AE for ; Fri, 16 Jul 2021 07:10:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235579AbhGPHM5 (ORCPT ); Fri, 16 Jul 2021 03:12:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231728AbhGPHMz (ORCPT ); Fri, 16 Jul 2021 03:12:55 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C085C06175F for ; Fri, 16 Jul 2021 00:10:00 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1m4Hyp-0005Ie-Qt; Fri, 16 Jul 2021 09:09:51 +0200 Received: from [2a0a:edc0:0:900:1d::77] (helo=ptz.office.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1m4Hyj-0000Av-Nv; Fri, 16 Jul 2021 09:09:45 +0200 Received: from ukl by ptz.office.stw.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1m4Hyj-0000CV-Mi; Fri, 16 Jul 2021 09:09:45 +0200 Date: Fri, 16 Jul 2021 09:09:43 +0200 From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= To: Billy Tsai Cc: "lee.jones@linaro.org" , "robh+dt@kernel.org" , "joel@jms.id.au" , "andrew@aj.id.au" , "thierry.reding@gmail.com" , "p.zabel@pengutronix.de" , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-aspeed@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , "linux-pwm@vger.kernel.org" , BMC-SW Subject: Re: [v9 2/2] pwm: Add Aspeed ast2600 PWM support Message-ID: <20210716070943.ayxkz2irkwhgincz@pengutronix.de> References: <20210709065217.6153-1-billy_tsai@aspeedtech.com> <20210709065217.6153-3-billy_tsai@aspeedtech.com> <20210715150533.vppkw5oiomkxmfrn@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="2f4lehdpjydeehv6" Content-Disposition: inline In-Reply-To: X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 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-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --2f4lehdpjydeehv6 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello Billy, On Fri, Jul 16, 2021 at 01:48:20AM +0000, Billy Tsai wrote: > On 2021/7/15, 11:06 PM, "Uwe Kleine-K=F6nig" > wrote: > > Another is: The PWM doesn't support duty_cycle 0, on such a request= the > > PWM is disabled which results in a constant inactive level. >=20 > > (This is correct, is it? Or does it yield a constant 0 level?) >=20 > Our pwm can support duty_cycle 0 by unset CLK_ENABLE. This has a slightly different semantic though. Some consumer might expect that the following sequence: pwm_apply(mypwm, { .period =3D 10000, .duty_cycle =3D 10000, .enabled =3D = true }) pwm_apply(mypwm, { .period =3D 10000, .duty_cycle =3D 0, .enabled =3D true= }) pwm_apply(mypwm, { .period =3D 10000, .duty_cycle =3D 10000, .enabled =3D = true }) results in the output being low for an integer multiple of 10 =B5s. This isn't given with setting CLK_ENABLE to zero, is it? (I didn't recheck, if the PWM doesn't complete periods on reconfiguration this doesn't matter much though.) Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | https://www.pengutronix.de/ | --2f4lehdpjydeehv6 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEfnIqFpAYrP8+dKQLwfwUeK3K7AkFAmDxMLQACgkQwfwUeK3K 7AmSUgf+KelGjfPXAW5sfbfcgNm/W3eNleFAUKPGThM4qsl47Gw8QytStuxO8Gsu POxq+PE8GfmzMNBWUqlIQnuadgbmLFQhOa2AY2E8xEeENDtZfAsiH8S18TvupZlF S/kxrlhoZ5zjpq+TkjVO0YIzK82a43quBj+WDAginCyqSKI/IE0HQdqScIdJFz6x 3bk23sSfI3EB91+dyFESGUVQ+5X9LVkeV+R8Wk1ytLh3hnUSN5X3nzSYECcH5qGr AMpjrqivGCGuIE6BBxPP2ZRP5b4iVFGTKm26cJ4uxIlEas2ZQndr3XKbRREjATuG C1vvl77dngONECSQqM5M6NyjVwzMGQ== =w9wF -----END PGP SIGNATURE----- --2f4lehdpjydeehv6--