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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3DD36C433EF for ; Mon, 15 Nov 2021 14:00:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1894A61B27 for ; Mon, 15 Nov 2021 14:00:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232087AbhKOOCj (ORCPT ); Mon, 15 Nov 2021 09:02:39 -0500 Received: from foss.arm.com ([217.140.110.172]:55666 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231937AbhKOOCN (ORCPT ); Mon, 15 Nov 2021 09:02:13 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4DBEA6D; Mon, 15 Nov 2021 05:59:18 -0800 (PST) Received: from [10.57.82.45] (unknown [10.57.82.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 60B483F766; Mon, 15 Nov 2021 05:59:16 -0800 (PST) Message-ID: <94d3f4e5-a698-134c-8264-55d31d3eafa6@arm.com> Date: Mon, 15 Nov 2021 13:59:11 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH v2 1/1] PCI: brcmstb: Use BIT() as __GENMASK() is for internal use only Content-Language: en-GB To: Andy Shevchenko , bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jim Quinlan , Nicolas Saenz Julienne , Florian Fainelli , Lorenzo Pieralisi , Rob Herring , =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= , Bjorn Helgaas References: <20211115112000.23693-1-andriy.shevchenko@linux.intel.com> From: Robin Murphy In-Reply-To: <20211115112000.23693-1-andriy.shevchenko@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-11-15 11:20, Andy Shevchenko wrote: > Use BIT() as __GENMASK() is for internal use only. The rationale > of switching to BIT() is to provide better generated code. The > GENMASK() against non-constant numbers may produce an ugly assembler > code. On contrary the BIT() is simply converted to corresponding shift > operation. FWIW, If you care about code quality and want the compiler to do the obvious thing, why not specify it as the obvious thing: u32 val = ~0 << msi->legacy_shift; Personally I don't think that abusing BIT() in the context of setting multiple bits is any better than abusing __GENMASK()... Robin. > Note, it's the only user of __GENMASK() in the kernel outside of its own realm. > > Fixes: 3baec684a531 ("PCI: brcmstb: Accommodate MSI for older chips") > Signed-off-by: Andy Shevchenko > --- > v2: switched to BIT() and elaborated why, hence not included tag > drivers/pci/controller/pcie-brcmstb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c > index 1fc7bd49a7ad..0c49fc65792c 100644 > --- a/drivers/pci/controller/pcie-brcmstb.c > +++ b/drivers/pci/controller/pcie-brcmstb.c > @@ -619,7 +619,7 @@ static void brcm_msi_remove(struct brcm_pcie *pcie) > > static void brcm_msi_set_regs(struct brcm_msi *msi) > { > - u32 val = __GENMASK(31, msi->legacy_shift); > + u32 val = ~(BIT(msi->legacy_shift) - 1); > > writel(val, msi->intr_base + MSI_INT_MASK_CLR); > writel(val, msi->intr_base + MSI_INT_CLR); >