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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BFD30C433DB for ; Wed, 24 Mar 2021 23:15:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9660B61A0F for ; Wed, 24 Mar 2021 23:15:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239003AbhCXXPS convert rfc822-to-8bit (ORCPT ); Wed, 24 Mar 2021 19:15:18 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:24291 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238989AbhCXXOp (ORCPT ); Wed, 24 Mar 2021 19:14:45 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-223-zjCwL4CNMgSnfl37WyP4uA-1; Wed, 24 Mar 2021 23:14:41 +0000 X-MC-Unique: zjCwL4CNMgSnfl37WyP4uA-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 24 Mar 2021 23:14:41 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.012; Wed, 24 Mar 2021 23:14:40 +0000 From: David Laight To: 'Arnd Bergmann' , Russell King CC: Arnd Bergmann , Nathan Chancellor , "Nick Desaulniers" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "clang-built-linux@googlegroups.com" Subject: RE: [PATCH] ARM: delay: avoid clang -Wtautological-constant warning Thread-Topic: [PATCH] ARM: delay: avoid clang -Wtautological-constant warning Thread-Index: AQHXH+dwZysyW/ACIU21groL09xJy6qTxo9A Date: Wed, 24 Mar 2021 23:14:40 +0000 Message-ID: References: <20210323132031.2858996-1-arnd@kernel.org> In-Reply-To: <20210323132031.2858996-1-arnd@kernel.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Arnd Bergmann > Sent: 23 March 2021 13:20 > Passing an 8-bit constant into delay() triggers a warning when building > with 'make W=1' using clang: > > drivers/clk/actions/owl-pll.c:182:2: error: result of comparison of constant 2000 with expression of > type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > udelay(pll_hw->delay); > ^~~~~~~~~~~~~~~~~~~~~ > arch/arm/include/asm/delay.h:84:9: note: expanded from macro 'udelay' > ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ > ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~ > arch/arm/mach-omap2/wd_timer.c:89:3: error: result of comparison of constant 2000 with expression of > type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > udelay(oh->class->sysc->srst_udelay); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Shut up the warning by adding a cast to a 64-bit number. A cast to 'int' > would usually be sufficient, but would fail to cause a link-time error > for large 64-bit constants. Adding 0u probably has the desired effect - without any side effects of a cast. David > > Signed-off-by: Arnd Bergmann > --- > arch/arm/include/asm/delay.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h > index 4f80b72372b4..1bb6417a3a83 100644 > --- a/arch/arm/include/asm/delay.h > +++ b/arch/arm/include/asm/delay.h > @@ -81,7 +81,7 @@ extern void __bad_udelay(void); > > #define udelay(n) \ > (__builtin_constant_p(n) ? \ > - ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ > + ((u64)(n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ > __const_udelay((n) * UDELAY_MULT)) : \ > __udelay(n)) > > -- > 2.29.2 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)