From owner-svn-src-head@freebsd.org Fri Sep 25 07:41:52 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 4AF673EDEE7; Fri, 25 Sep 2020 07:41:52 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4ByP4c1J0gz4mYF; Fri, 25 Sep 2020 07:41:52 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 014AFFC8F; Fri, 25 Sep 2020 07:41:52 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 08P7fpUB001726; Fri, 25 Sep 2020 07:41:51 GMT (envelope-from avg@FreeBSD.org) Received: (from avg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 08P7fpUb001725; Fri, 25 Sep 2020 07:41:51 GMT (envelope-from avg@FreeBSD.org) Message-Id: <202009250741.08P7fpUb001725@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: avg set sender to avg@FreeBSD.org using -f From: Andriy Gapon Date: Fri, 25 Sep 2020 07:41:51 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r366142 - head/sys/arm/allwinner X-SVN-Group: head X-SVN-Commit-Author: avg X-SVN-Commit-Paths: head/sys/arm/allwinner X-SVN-Commit-Revision: 366142 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Sep 2020 07:41:52 -0000 Author: avg Date: Fri Sep 25 07:41:51 2020 New Revision: 366142 URL: https://svnweb.freebsd.org/changeset/base/366142 Log: aw_pwm: add a check and some comments related to long periods The hardware supports periods as long as 196 seconds[*] when using the maximal prescaling of 72000 and maximum cycle count of 2^16. But the code becomes incorrect when the period length approaches 1 second. That's because of things like NS_PER_SEC / period. [*] At the same time I must note that the KPI provides for maximum period of about 4 seconds (2^32 nanoseconds). MFC after: 2 weeks Modified: head/sys/arm/allwinner/aw_pwm.c Modified: head/sys/arm/allwinner/aw_pwm.c ============================================================================== --- head/sys/arm/allwinner/aw_pwm.c Fri Sep 25 07:40:56 2020 (r366141) +++ head/sys/arm/allwinner/aw_pwm.c Fri Sep 25 07:41:51 2020 (r366142) @@ -259,6 +259,20 @@ aw_pwm_channel_config(device_t dev, u_int channel, u_i period_freq = NS_PER_SEC / period; if (period_freq > AW_PWM_MAX_FREQ) return (EINVAL); + + /* + * FIXME. The hardware is capable of sub-Hz frequencies, that is, + * periods longer than a second. But the current code cannot deal + * with those properly. + */ + if (period_freq == 0) + return (EINVAL); + + /* + * FIXME. There is a great loss of precision when the period and the + * duty are near 1 second. In some cases period_freq and duty_freq can + * be equal even if the period and the duty are significantly different. + */ duty_freq = NS_PER_SEC / duty; if (duty_freq < period_freq) { device_printf(sc->dev, "duty < period\n");