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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 623E4C433B4 for ; Wed, 21 Apr 2021 13:48:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 330ED61439 for ; Wed, 21 Apr 2021 13:48:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235199AbhDUNtH (ORCPT ); Wed, 21 Apr 2021 09:49:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234768AbhDUNtD (ORCPT ); Wed, 21 Apr 2021 09:49:03 -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 0AA6EC06174A for ; Wed, 21 Apr 2021 06:48:30 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lZDDP-0002bJ-SZ; Wed, 21 Apr 2021 15:48:27 +0200 Received: from ukl by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1lZDDO-00018U-EK; Wed, 21 Apr 2021 15:48:26 +0200 Date: Wed, 21 Apr 2021 15:48:25 +0200 From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= To: Claudiu Beznea , Thierry Reding , Lee Jones Cc: linux-pwm@vger.kernel.org, Alexandre Belloni , Nicolas Ferre , Ludovic Desroches , kernel@pengutronix.de, linux-arm-kernel@lists.infradead.org Subject: Re: overflow and wrong timeout errors in pwm-atmel Message-ID: <20210421134825.powx5tvqvce32fho@pengutronix.de> References: <20210420095118.1571344-1-u.kleine-koenig@pengutronix.de> <20210421092606.1634092-1-u.kleine-koenig@pengutronix.de> <20210421110336.bd5s6e2kjxqilddi@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="hunmctkm5vrpq4ne" Content-Disposition: inline In-Reply-To: <20210421110336.bd5s6e2kjxqilddi@pengutronix.de> X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 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-pwm@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org --hunmctkm5vrpq4ne Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 21, 2021 at 01:03:36PM +0200, Uwe Kleine-K=F6nig wrote: > On Wed, Apr 21, 2021 at 11:26:08AM +0200, Uwe Kleine-K=F6nig wrote: > > With these three patches PWM_DEBUG is now happy. (At least I couldn't > > trigger a warning any more. I think there are still a few problems with > > integer overflows.) >=20 > BTW, setting the period to 138350580899 (with a clock rate of 133333333 > Hz) results in setting period=3D0 because >=20 > state->period * clkrate =3D > 138350580899 * 133333333 =3D > 40254751 (discarded from 18446744073749806367). As a first remedy the following could be done: diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c index 38d86340201c..02d69fa5f7d2 100644 --- a/drivers/pwm/pwm-atmel.c +++ b/drivers/pwm/pwm-atmel.c @@ -199,6 +199,11 @@ static int atmel_pwm_calculate_cprd_and_pres(struct pw= m_chip *chip, unsigned long long cycles =3D state->period; int shift; =20 + if (fls(cycles) + fls(clkrate) > 64) { + dev_err(chip->dev, "period to big to calculate HW parameters\n"); + return -EINVAL; + } + /* Calculate the period cycles and prescale value */ cycles *=3D clkrate; do_div(cycles, NSEC_PER_SEC); Is this sensible? (Actually I'd prefer to just continue with period =3D (ULL(1) << (64 - fls(clkrate))) - 1 according to the motto to yield the highest possible period, but this function has another error path that returns -EINVAL so this would be inconsistent.) Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | https://www.pengutronix.de/ | --hunmctkm5vrpq4ne Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEfnIqFpAYrP8+dKQLwfwUeK3K7AkFAmCALSYACgkQwfwUeK3K 7Almrwf/c+tV70NNg925X+gBlg69oaELR8U7TwSV0FF2Pfxk2qyPGcDnxRFBiBrH WDmcQ/mfk/qO7Jn2Y7Jmf1S4ZMX80ELFfHLEP1nMYk2jIB/77lmBWkAlNvSnc5Ak +NoINHyO735sVHaHQlEBUBDeWdElsmzDD/dxJTbGpDNWQnQb+xzR5yAYsieLC1o9 JjyQ/Y9NM7471W54jzF3xHwo9tSMIUaPhm2aM66XDsQCGzgzn+h/Ss4LV1lTAPqg gMU907QtjzkL5/fRBqud80wmVOvkXs++x7GgDX5QCR5qRo1sI0IyXJvUU+AemRBa fjRg0uBCeu1g7CJOrT8RtMRf9GGvxQ== =45Q3 -----END PGP SIGNATURE----- --hunmctkm5vrpq4ne--