From patchwork Wed Apr 3 15:14:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?Jernej_=C5=A0krabec?= X-Patchwork-Id: 10884005 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3D0561390 for ; Wed, 3 Apr 2019 15:14:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 208E120602 for ; Wed, 3 Apr 2019 15:14:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 13A80285D9; Wed, 3 Apr 2019 15:14:40 +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=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BED7620602 for ; Wed, 3 Apr 2019 15:14:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=OBTyTE3GtZ0/FlsuSDKX1ANUcWmtKFG5duPxSRqR8oU=; b=f8rlHjyhmRwJMw MsYAmF+X1F+UhjlYLEwliZqtHTPgMvo30lRXhE3CcriIMxZZyvWTtVonoDvUgCmjP80J+W/d86S6h 8olKwNexPnUK63/6zaqQ+6iQTS2tYgIbuG1FEnkqNAl5QImnMkEyqbl+cXJ5AZo9R5XwfufBd/r5/ W8+jB5vPEiERprt9+Hrnc1490pK7eSPNeuagWKM2vVRx/V51iiB2+2AjmvoIHLHYJif5AvQkBSEHZ aYZ48Mjk25OAdXrIpzi21uYgQMINcV83a1n1261dJac4QXM/XIYG1ZxrskEDl7gPxqUTImb+sU3xL zJE40aAb861kBC2ggvfQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hBhb3-0004SV-OR; Wed, 03 Apr 2019 15:14:37 +0000 Received: from mailoutvs44.siol.net ([185.57.226.235] helo=mail.siol.net) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hBhal-00044L-8h for linux-arm-kernel@lists.infradead.org; Wed, 03 Apr 2019 15:14:20 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.siol.net (Postfix) with ESMTP id 29BA55229E9; Wed, 3 Apr 2019 17:14:17 +0200 (CEST) X-Virus-Scanned: amavisd-new at psrvmta09.zcs-production.pri Received: from mail.siol.net ([127.0.0.1]) by localhost (psrvmta09.zcs-production.pri [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id z3kRh_h6lRjd; Wed, 3 Apr 2019 17:14:16 +0200 (CEST) Received: from mail.siol.net (localhost [127.0.0.1]) by mail.siol.net (Postfix) with ESMTPS id E058B5229DF; Wed, 3 Apr 2019 17:14:16 +0200 (CEST) Received: from localhost.localdomain (cpe-86-58-52-202.static.triera.net [86.58.52.202]) (Authenticated sender: 031275009) by mail.siol.net (Postfix) with ESMTPSA id 8C9595229E9; Wed, 3 Apr 2019 17:14:14 +0200 (CEST) From: Jernej Skrabec To: maxime.ripard@bootlin.com, wens@csie.org Subject: [PATCH v2 2/2] clk: sunxi-ng: nkmp: Explain why zero width check is needed Date: Wed, 3 Apr 2019 17:14:04 +0200 Message-Id: <20190403151404.26542-3-jernej.skrabec@siol.net> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190403151404.26542-1-jernej.skrabec@siol.net> References: <20190403151404.26542-1-jernej.skrabec@siol.net> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190403_081419_462013_D4E01143 X-CRM114-Status: UNSURE ( 8.76 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jernej.skrabec@siol.net, sboyd@kernel.org, mturquette@baylibre.com, linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Add an explanation why zero width check is needed when generating factor mask using GENMASK() macro. Signed-off-by: Jernej Skrabec --- drivers/clk/sunxi-ng/ccu_nkmp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/clk/sunxi-ng/ccu_nkmp.c b/drivers/clk/sunxi-ng/ccu_nkmp.c index 69dfc6de1c4e..cbcdf664f336 100644 --- a/drivers/clk/sunxi-ng/ccu_nkmp.c +++ b/drivers/clk/sunxi-ng/ccu_nkmp.c @@ -186,6 +186,12 @@ static int ccu_nkmp_set_rate(struct clk_hw *hw, unsigned long rate, ccu_nkmp_find_best(parent_rate, rate, &_nkmp); + /* + * If width is 0, GENMASK() macro may not generate expected mask (0) + * as it falls under undefined behaviour by C standard due to shifts + * which are equal or greater than width of left operand. This can + * be easily avoided by explicitly checking if width is 0. + */ if (nkmp->n.width) n_mask = GENMASK(nkmp->n.width + nkmp->n.shift - 1, nkmp->n.shift);