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=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 0763EC433ED for ; Tue, 11 May 2021 17:35:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C67DF61363 for ; Tue, 11 May 2021 17:35:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231587AbhEKRgQ (ORCPT ); Tue, 11 May 2021 13:36:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:54484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231329AbhEKRgP (ORCPT ); Tue, 11 May 2021 13:36:15 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 20864611CA; Tue, 11 May 2021 17:35:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620754509; bh=YPhRLTxOgdPzo1iZN2FPl/ndFofc60gotWgeCGFIYOg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UmtMPRNKB5D7IhY0pfXWfAi/zQ0QvTZ7GRfUhVUWWGpcIBbl/c6RxnpfXoqyHX1tq 4ypfMShci2envDbJXDBdPQlzKaG7lwQwlgOmU5y8GhZxdldjl3h/EZxMFJrBryYA8g Xy4OfvGRFoOmsbaz7x7yGXuNWarikVqwuybXdrT51dvPkKxe6mjHctxcaBTdM522I9 +rjFLXPW1pbTkxvOYaVEjwKiuIgs3+/niVpMrJywj9ML8deTOaGjjL8vdsD1SM9AFh MWMlxx/KSH4aaH7nvSjs6GLxYHv37/YgFKUJLEI+yufvxDaMtyaShMEMAW33omxRoV P4qOnCVsyK6tA== Date: Tue, 11 May 2021 10:35:03 -0700 From: Nathan Chancellor To: Dmitry Osipenko Cc: Krzysztof Kozlowski , kernel test robot , Thierry Reding , Jonathan Hunter , Nick Desaulniers , clang-built-linux@googlegroups.com, kbuild-all@lists.01.org, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org Subject: Re: [PATCH v1 2/2] memory: tegra: Enable compile testing for all drivers Message-ID: References: <20210510213729.7095-3-digetx@gmail.com> <202105112125.VctfC6sX-lkp@intel.com> <06addbf3-0090-b76f-65cf-e0c10d284c69@canonical.com> <3ab5d50b-4955-7144-5d1d-d44cb0892d65@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3ab5d50b-4955-7144-5d1d-d44cb0892d65@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On Tue, May 11, 2021 at 07:00:34PM +0300, Dmitry Osipenko wrote: > 11.05.2021 18:31, Krzysztof Kozlowski пишет: > ... > ~~~~~~~~~~~~~~~~~~~~~^ > >>>>> drivers/memory/tegra/tegra124-emc.c:802:26: warning: implicit conversion from 'unsigned long' to 'u32' (aka 'unsigned int') changes value from 18446744071562067985 to 2147483665 [-Wconstant-conversion] > >>> emc_ccfifo_writel(emc, EMC_ZQ_CAL_LONG_CMD_DEV0, EMC_ZQ_CAL); > >>> ~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~ > >>> drivers/memory/tegra/tegra124-emc.c:154:36: note: expanded from macro 'EMC_ZQ_CAL_LONG_CMD_DEV0' > >>> (DRAM_DEV_SEL_0 | EMC_ZQ_CAL_LONG | EMC_ZQ_CAL_CMD) > >>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~ > >>> 13 warnings generated. > >> > >> This doesn't look like a useful warning from clang, it should see that > >> the constant value itself isn't truncated, hence it should be a problem > >> of clang. Do you think it's okay to ignore this nonsense? > > > > I admit I also do not see the real issue here. The DRAM_DEV_SEL_0 fits > > in u32 and there is no other bitwise arithmetic than just OR, so why > > clang assumes it can have 32 most signifcant bits toggled on? > > > > +Cc Nathan and Nick, > > Maybe you could shed some light here on this warning? > > > > Dmitry, > > In general you should not ignore it because: > > 1. This breaks allyesconfig with clang on powerpc (or it is one of the > > stoppers), > > 2. We might want in some future to build it with clang. > > I meant to ignore it from the perspective of the memory drivers, i.e. it > likely should be fixed in clang and not worked around in the code. Thank > you for pinging the right people. I do not think this is a bug in clang, gcc warns the same (just not here in this case): https://godbolt.org/z/e9GWobMnd DRAM_DEV_SEL_0 and DRAM_DEV_SEL_1 are implicitly signed integers because there is no suffix on the literal 1. DRAM_DEV_SEL_0 is 2 << 30, which can be turned into 1 << 31. That is equal to INT_MAX + 1, which then overflows and becomes INT_MIN (undefined behavior). INT_MIN is then promoted to unsigned long because EMC_ZQ_CAL_LONG and EMC_ZQ_CAL_CMD are unsigned long due to the BIT macro, resulting in the gigantic number that clang reports above. I assume that this driver only runs on hardware where unsigned int is the same size as unsigned long, meaning this problem is merely theoretical? Regardless, defining DRAM_DEV_SEL_{0,1} with the BIT macro fixes the warning for me and should make everything work as expected. diff --git a/drivers/memory/tegra/tegra124-emc.c b/drivers/memory/tegra/tegra124-emc.c index 5699d909abc2..a21ca8e0841a 100644 --- a/drivers/memory/tegra/tegra124-emc.c +++ b/drivers/memory/tegra/tegra124-emc.c @@ -272,8 +272,8 @@ #define EMC_PUTERM_ADJ 0x574 #define DRAM_DEV_SEL_ALL 0 -#define DRAM_DEV_SEL_0 (2 << 30) -#define DRAM_DEV_SEL_1 (1 << 30) +#define DRAM_DEV_SEL_0 BIT(31) +#define DRAM_DEV_SEL_1 BIT(30) #define EMC_CFG_POWER_FEATURES_MASK \ (EMC_CFG_DYN_SREF | EMC_CFG_DRAM_ACPD | EMC_CFG_DRAM_CLKSTOP_SR | \