From patchwork Thu Oct 5 21:38:42 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Zanoni, Paulo R" X-Patchwork-Id: 9988037 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B974560247 for ; Thu, 5 Oct 2017 21:39:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AAFE828CEA for ; Thu, 5 Oct 2017 21:39:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9FBB028D48; Thu, 5 Oct 2017 21:39:09 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 5D68328CEA for ; Thu, 5 Oct 2017 21:39:09 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CB2ED6E8AD; Thu, 5 Oct 2017 21:39:08 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1719F6E8AD for ; Thu, 5 Oct 2017 21:39:08 +0000 (UTC) Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Oct 2017 14:39:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,482,1500966000"; d="scan'208";a="907183358" Received: from przanoni-mobl.amr.corp.intel.com ([10.254.176.144]) by FMSMGA003.fm.intel.com with ESMTP; 05 Oct 2017 14:39:05 -0700 From: Paulo Zanoni To: intel-gfx@lists.freedesktop.org Date: Thu, 5 Oct 2017 18:38:42 -0300 Message-Id: <20171005213842.11423-2-paulo.r.zanoni@intel.com> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20171005213842.11423-1-paulo.r.zanoni@intel.com> References: <20171005213842.11423-1-paulo.r.zanoni@intel.com> Cc: Paulo Zanoni , Rodrigo Vivi Subject: [Intel-gfx] [PATCH 2/2] drm/i915: avoid division by zero on cnl_calc_wrpll_link X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP If for some unexpected reason the registers all read zero it's better to WARN and return instead of dividing by zero and completely freezing the machine. I don't expect this to happen in the wild with the current code, but I accidentally triggered the division by zero while doing some debugging in an unusual environment. Cc: Rodrigo Vivi Signed-off-by: Paulo Zanoni Reviewed-by: Rodrigo Vivi --- drivers/gpu/drm/i915/intel_ddi.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c index f7c91bb..be86eb6 100644 --- a/drivers/gpu/drm/i915/intel_ddi.c +++ b/drivers/gpu/drm/i915/intel_ddi.c @@ -1220,6 +1220,9 @@ static int cnl_calc_wrpll_link(struct drm_i915_private *dev_priv, dco_freq += (((cfgcr0 & DPLL_CFGCR0_DCO_FRACTION_MASK) >> DPLL_CFGCR0_DCO_FRACTION_SHIFT) * ref_clock) / 0x8000; + if (WARN_ON(p0 == 0 || p1 == 0 || p2 == 0)) + return 0; + return dco_freq / (p0 * p1 * p2 * 5); }