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=-8.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 7C14AC433E7 for ; Mon, 31 Aug 2020 11:27:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58F852098B for ; Mon, 31 Aug 2020 11:27:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="KcY1b2hA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726913AbgHaL1j (ORCPT ); Mon, 31 Aug 2020 07:27:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725972AbgHaL0o (ORCPT ); Mon, 31 Aug 2020 07:26:44 -0400 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E5E7AC061755; Mon, 31 Aug 2020 04:02:11 -0700 (PDT) Received: by mail-ej1-x642.google.com with SMTP id p9so2166391ejf.6; Mon, 31 Aug 2020 04:02:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=y2QxnqD/1GqUYAZY6NBKUAuDj/nq3iGjxOKV37yba/w=; b=KcY1b2hAsR6BY9OMaCp/0Sm28/cROsMbs1Cgr3ZdYTkegiIzkP1pGDhic1pPB8FRvC pBRwYuya3qddJQ/NLNdhe+C0kcj/vLoW2bATm2j9d5+y1tJvzAv8EQLKto6+kTt/O+xE cjMeZbDJGktxm5YgrYCw8BWmuNM4w05XLpmYoX3pNIfFNF/Pv7Gi8F5p+jJVsnlZDGju tJLDIFBN5E/dT4ls5RRfcWLxqXNVnz6i2LiUfdeOF0vvYwPiAUnP17ILIqNZ50PCsASR 6y1g9SLmTx1z5dIIJ6c9CLpn3X+WidNJbo4YssIV/QPcEp+FlT/geWsYD9a27Qr3iiU3 /caw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=y2QxnqD/1GqUYAZY6NBKUAuDj/nq3iGjxOKV37yba/w=; b=f0gdRHXKG+KvHlQG2K/egZKpaUhMy1grfwoNfskX9kPEaKSdUZVn1noWWSC01DWtj4 erpkr7XKJhSPFz8KulSF1E2Ufrqlk19d8F70KgX3jQB7V6beuNo6kamNOzFiko0KYmE6 tOrlfuzVMzu6nQk8NJW6MmmRBdNFZ07VSEUbxmqWlDhv9OGzO6y64WpXCHmB7+0YunIy oXcJrl/PeiQ/VcqVnZj5wAqSsU1qEXTFNGg4fX+cze1pJkPZ8Q69078mkAUyUZsnsQL3 ekNuYQMETgHmOd6abs8vCyq0kUDphYP0jcErhL/TNLzooybIB+tfeeJ8PwavUGFG02+i xjtA== X-Gm-Message-State: AOAM532ctAOqESRxsJw7do/tccgXpf+NUo3PoLyXDYf4mo1PdwLDCHlt Qh09x4k+dlE3/9wd9kI1gCA= X-Google-Smtp-Source: ABdhPJxRwTwdJG8coU1+OFQeCDGe/IHZIporIBSIsMhzEvsSXTEcZbztHAA8FX0DsHxcCx4MpcjJmQ== X-Received: by 2002:a17:906:1154:: with SMTP id i20mr565986eja.243.1598871729707; Mon, 31 Aug 2020 04:02:09 -0700 (PDT) Received: from localhost ([62.96.65.119]) by smtp.gmail.com with ESMTPSA id j1sm5708906edf.44.2020.08.31.04.02.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2020 04:02:08 -0700 (PDT) Date: Mon, 31 Aug 2020 13:02:07 +0200 From: Thierry Reding To: Hans de Goede Cc: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Ville =?utf-8?B?U3lyasOkbMOk?= , "Rafael J . Wysocki" , Len Brown , linux-pwm@vger.kernel.org, intel-gfx , dri-devel@lists.freedesktop.org, Andy Shevchenko , Mika Westerberg , linux-acpi@vger.kernel.org Subject: Re: [PATCH v8 04/17] pwm: lpss: Add range limit check for the base_unit register value Message-ID: <20200831110207.GB1688464@ulmo> References: <20200830125753.230420-1-hdegoede@redhat.com> <20200830125753.230420-5-hdegoede@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="1LKvkjL3sHcu1TtY" Content-Disposition: inline In-Reply-To: <20200830125753.230420-5-hdegoede@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org --1LKvkjL3sHcu1TtY Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Aug 30, 2020 at 02:57:40PM +0200, Hans de Goede wrote: > When the user requests a high enough period ns value, then the > calculations in pwm_lpss_prepare() might result in a base_unit value of 0. >=20 > But according to the data-sheet the way the PWM controller works is that > each input clock-cycle the base_unit gets added to a N bit counter and > that counter overflowing determines the PWM output frequency. Adding 0 > to the counter is a no-op. The data-sheet even explicitly states that > writing 0 to the base_unit bits will result in the PWM outputting a > continuous 0 signal. >=20 > When the user requestes a low enough period ns value, then the > calculations in pwm_lpss_prepare() might result in a base_unit value > which is bigger then base_unit_range - 1. Currently the codes for this > deals with this by applying a mask: >=20 > base_unit &=3D (base_unit_range - 1); >=20 > But this means that we let the value overflow the range, we throw away the > higher bits and store whatever value is left in the lower bits into the > register leading to a random output frequency, rather then clamping the > output frequency to the highest frequency which the hardware can do. >=20 > This commit fixes both issues by clamping the base_unit value to be > between 1 and (base_unit_range - 1). >=20 > Fixes: 684309e5043e ("pwm: lpss: Avoid potential overflow of base_unit") > Reviewed-by: Andy Shevchenko > Signed-off-by: Hans de Goede > --- > Changes in v5: > - Use clamp_val(... instead of clam_t(unsigned long long, ... >=20 > Changes in v3: > - Change upper limit of clamp to (base_unit_range - 1) > - Add Fixes tag > --- > drivers/pwm/pwm-lpss.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) Acked-by: Thierry Reding --1LKvkjL3sHcu1TtY Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAl9M2K8ACgkQ3SOs138+ s6FvmhAAidTtMFsrm8acDCUZfp1D48n+LAL/edmqIHFYYgVuC+TyEnpQvACrUc8u SMgxqEtVGql7SItwicnNAKo8d1HliKdeQPLxlLVjpWBaNGJisn1c0Pau+X3oB4rq 7Qnmkfo6qDKJRm0T13JyNB+3GtQkbC2je7/cFu3UN+aaHEVL/MUGJb+NJdrdcWaA oSomXdi2RJylkudfQuD4QleIst9pI2N5q1FUz0R15fOx2fagjOQpD6bKXvpCkIeY QTUafA1Y7ymd7cpfKV4y38jglJ1KfFvkuxqHhLWJiMmt67v/sOdsuSzzI2PGNkge TDLr9/5nfnNBVRZ3W4BUsC0+hsVaENyRdIPUzu/gtpJ1N6eEkLi3YpM7EyeDlA2Z yZAj39b0ea5jPd6eQuPuVyDkiZnUypAjmytIwG88ABmuuLlvTnlNKcJ41cM1ZwZr VMjy/gosQPaJpnE51W+g1rsjVzFhVy1yxXoWKwVfV+nX+jai3uzZD9dFH+ydYZe4 PUgsW2/J5p0szzo08PJmXZalfN+e0fhrV1OZMwVZFLLK2Ao6W36rVJzeBZoa+zWL Rsuf0YfhFzLDcDH4fCiU3jU4TrDfCycx59B+sggHC0LwpKDP8n3BxRMVuAat+v9p BNGzjn/3fs3vtixtQTa7AG0yFuEEPKmrJgVoF9KsquZrNxBg9Qs= =zX3v -----END PGP SIGNATURE----- --1LKvkjL3sHcu1TtY--