From patchwork Mon Jan 2 09:16:44 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Shevchenko X-Patchwork-Id: 710104 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3tsWfr6SfYz9t15 for ; Mon, 2 Jan 2017 20:16:52 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755228AbdABJQw (ORCPT ); Mon, 2 Jan 2017 04:16:52 -0500 Received: from mga01.intel.com ([192.55.52.88]:9181 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754829AbdABJQw (ORCPT ); Mon, 2 Jan 2017 04:16:52 -0500 Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga101.fm.intel.com with ESMTP; 02 Jan 2017 01:16:51 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,432,1477983600"; d="scan'208";a="804240713" Received: from black.fi.intel.com ([10.237.72.28]) by FMSMGA003.fm.intel.com with ESMTP; 02 Jan 2017 01:16:49 -0800 Received: by black.fi.intel.com (Postfix, from userid 1003) id 80A2087; Mon, 2 Jan 2017 11:16:48 +0200 (EET) From: Andy Shevchenko To: Thierry Reding , linux-pwm@vger.kernel.org, Mika Westerberg , Linus Torvalds , Ilkka Koskinen Cc: Andy Shevchenko Subject: [PATCH v2 1/4] pwm: lpss: Avoid potential overflow of base_unit Date: Mon, 2 Jan 2017 11:16:44 +0200 Message-Id: <20170102091647.86910-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170102091647.86910-1-andriy.shevchenko@linux.intel.com> References: <20170102091647.86910-1-andriy.shevchenko@linux.intel.com> Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org The resolution of base_unit is derived from base_unit_bits and thus must be equal to (2^base_unit_bits - 1). Otherwise frequency and therefore base_unit might potentially overflow. Prevent the above by substracting 1 in all cases where base_unit_bits or derivative is used. Reviewed-by: Mika Westerberg Signed-off-by: Andy Shevchenko --- drivers/pwm/pwm-lpss.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 72c0bce5a75c..8642feeb8abd 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -102,7 +102,7 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm, * The equation is: * base_unit = round(base_unit_range * freq / c) */ - base_unit_range = BIT(lpwm->info->base_unit_bits); + base_unit_range = BIT(lpwm->info->base_unit_bits) - 1; freq *= base_unit_range; base_unit = DIV_ROUND_CLOSEST_ULL(freq, c); @@ -117,8 +117,8 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm, 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 &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT); + base_unit &= base_unit_range; ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT; ctrl |= on_time_div; pwm_lpss_write(pwm, ctrl);