From patchwork Thu Sep 3 10:51:01 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans de Goede X-Patchwork-Id: 11753089 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8F1AC109A for ; Thu, 3 Sep 2020 10:51:43 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 6D653206A5 for ; Thu, 3 Sep 2020 10:51:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="An/Xrhyy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D653206A5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C80FC6E97E; Thu, 3 Sep 2020 10:51:40 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id ED2D66E97E for ; Thu, 3 Sep 2020 10:51:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599130299; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZukzWkoKOICgMwClnkSHfjft9LoCEglKBEzHtiqOOV4=; b=An/XrhyyA/qL6sJhUpfGhbx8+hOVtKvqgy4MiDC/hDiV7CZvPKS76HvrXRAZpZkFBnVC7E GaxE6MqXlz2SYRdMzq9TAtw9VghBzyjoXNOoNAhkoiZlq97nzesmg1wSni83kz+aDiKG74 gA7g5nYnLWoZJE5SBRE7p5t5jWXCYSs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-506-MZSAfRjuPfC7YFwMhi2GjA-1; Thu, 03 Sep 2020 06:51:35 -0400 X-MC-Unique: MZSAfRjuPfC7YFwMhi2GjA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 287848030BD; Thu, 3 Sep 2020 10:51:33 +0000 (UTC) Received: from x1.localdomain.com (ovpn-115-4.ams2.redhat.com [10.36.115.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 62B41784A8; Thu, 3 Sep 2020 10:51:29 +0000 (UTC) From: Hans de Goede To: Thierry Reding , =?utf-8?q?Uwe_Kleine-K=C3=B6n?= =?utf-8?q?ig?= , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , =?utf-8?b?VmlsbGUgU3lyasOkbMOk?= , "Rafael J . Wysocki" , Len Brown Subject: [PATCH v9 04/17] pwm: lpss: Add range limit check for the base_unit register value Date: Thu, 3 Sep 2020 12:51:01 +0200 Message-Id: <20200903105114.9969-5-hdegoede@redhat.com> In-Reply-To: <20200903105114.9969-1-hdegoede@redhat.com> References: <20200903105114.9969-1-hdegoede@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, linux-acpi@vger.kernel.org, intel-gfx , dri-devel@lists.freedesktop.org, Hans de Goede , Andy Shevchenko , Mika Westerberg Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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. 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. 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: base_unit &= (base_unit_range - 1); 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. This commit fixes both issues by clamping the base_unit value to be between 1 and (base_unit_range - 1). Fixes: 684309e5043e ("pwm: lpss: Avoid potential overflow of base_unit") Reviewed-by: Andy Shevchenko Acked-by: Thierry Reding Signed-off-by: Hans de Goede --- Changes in v5: - Use clamp_val(... instead of clam_t(unsigned long long, ... 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(-) diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 43b1fc634af1..da9bc3d10104 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -97,6 +97,8 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, freq *= base_unit_range; base_unit = DIV_ROUND_CLOSEST_ULL(freq, c); + /* base_unit must not be 0 and we also want to avoid overflowing it */ + base_unit = clamp_val(base_unit, 1, base_unit_range - 1); on_time_div = 255ULL * duty_ns; do_div(on_time_div, period_ns); @@ -105,7 +107,6 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, orig_ctrl = ctrl = pwm_lpss_read(pwm); ctrl &= ~PWM_ON_TIME_DIV_MASK; ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT); - base_unit &= (base_unit_range - 1); ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT; ctrl |= on_time_div;