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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3312BC433EF for ; Thu, 7 Jul 2022 10:45:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235039AbiGGKpr (ORCPT ); Thu, 7 Jul 2022 06:45:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39314 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234834AbiGGKpn (ORCPT ); Thu, 7 Jul 2022 06:45:43 -0400 Received: from mail-lj1-x236.google.com (mail-lj1-x236.google.com [IPv6:2a00:1450:4864:20::236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ACDAD4D4C0; Thu, 7 Jul 2022 03:45:41 -0700 (PDT) Received: by mail-lj1-x236.google.com with SMTP id y18so10859731ljj.6; Thu, 07 Jul 2022 03:45:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=WY98p2xpQdOFXmhJtt3xHyGiLiAUhi6XRf4hr9Uc3Wg=; b=b6GFfkBqjaMf2ocm+NmB4Pdq8BftwMkyn64oPaQ4MV4pvFzFkwxMEQeq6P80Hm4/xV qZ+8LuyU5wRQNERGgQNFjcHh58vvfaC0ptqNORWmxffraiT9/DjbcHTSFTsFBlux58Ot XhtqsfAx1Sa2gM/tjlsL0QsZtd9LNBgjw9CnnsV557EhbpHb9gCv8v2p+Oj+GmTrlkqp mUp+nL+5dVYNjaxqq1uCJh+k/gsHSTvygVI9uMaKcsKBGCdHzMWvDPsDHQivCRNcB3z5 282ePxgRE2AokBxYCEN4Y+8PqCSOtSZbzmUbIGk4eL7kv/uEwV39B6EvqmW8CS1gOdOi UC1w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=WY98p2xpQdOFXmhJtt3xHyGiLiAUhi6XRf4hr9Uc3Wg=; b=5Eo/0Z9lE0dnEeA9CuAdzgT3ij2ITH1jbtYNGQ3ygRTp6jZ+ZR9exxaGcxsdWLOp43 QEfLLPrepVslpODTt1c/qMl2IB5pR1uJbrnRoxK3I/RrgsGUtsG5sjFEaxpM0rxv7VZB 6yFa4tvQySbXnXgQdXI5P2XVZ2T838olFWqvhX7ardxLCW9rniWNuC3chL9ntyBbv9VU gTJ+ctTszv+uIF5a1LzpKx5VHuD6KJjeLh9OGF4MPEtyXszsyNiZB4rrTWvvgA8ipBpo qsruG5dF5+MsgNhHJ+lXuQf0T4SFgwiFleFinWHRUzJWDuzuCYv0LZ4ZX6Bb70Rb0PS8 AQpg== X-Gm-Message-State: AJIora+KWHbZBHMQ09F9agduePiLBnsypQP2ImH/lJvQ7Ytt3b/WMIi9 7Ccx7XfzwyGkgpAJZ45OVhc= X-Google-Smtp-Source: AGRyM1u/4QG+lv01OuNQRv5dICfp1iMojBGdOQCB054Of0nHO6eJIDlEiA+XLi20gZMrDBLB66OBnA== X-Received: by 2002:a05:651c:158a:b0:25d:1cc9:3ce7 with SMTP id h10-20020a05651c158a00b0025d1cc93ce7mr13652854ljq.450.1657190739851; Thu, 07 Jul 2022 03:45:39 -0700 (PDT) Received: from mobilestation ([95.79.140.178]) by smtp.gmail.com with ESMTPSA id g2-20020a056512118200b0047f701f6d09sm6766233lfr.184.2022.07.07.03.45.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Jul 2022 03:45:37 -0700 (PDT) Date: Thu, 7 Jul 2022 13:45:33 +0300 From: Serge Semin To: Marc Zyngier Cc: Samuel Holland , Thomas Gleixner , Andy Shevchenko , Bartosz Golaszewski , Bjorn Helgaas , Boris Ostrovsky , Borislav Petkov , Broadcom internal kernel review list , Chris Zankel , Colin Ian King , Dave Hansen , Dexuan Cui , Florian Fainelli , Guo Ren , "H. Peter Anvin" , Haiyang Zhang , Helge Deller , Ingo Molnar , Ivan Kokshaysky , "James E.J. Bottomley" , Jan Beulich , Joerg Roedel , Juergen Gross , Julia Lawall , "K. Y. Srinivasan" , Kees Cook , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Linus Walleij , Lorenzo Pieralisi , Mark Rutland , Matt Turner , Max Filippov , Maximilian Heyne , Oleksandr Tyshchenko , Rich Felker , Richard Henderson , Rikard Falkeborn , Rob Herring , Russell King , Stefano Stabellini , Stephen Hemminger , Sven Schnelle , Thomas Bogendoerfer , Wei Liu , Wei Xu , Will Deacon , Yoshinori Sato , iommu@lists.linux-foundation.org, iommu@lists.linux.dev, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-pci@vger.kernel.org, linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org, x86@kernel.org, xen-devel@lists.xenproject.org, kernel test robot Subject: Re: [PATCH v3 1/8] irqchip/mips-gic: Only register IPI domain when SMP is enabled Message-ID: <20220707104533.7iakliv2f5i2qi33@mobilestation> References: <20220701200056.46555-1-samuel@sholland.org> <20220701200056.46555-2-samuel@sholland.org> <20220705135243.ydbwfo4kois64elr@mobilestation> <87czehmiwt.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87czehmiwt.wl-maz@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 07, 2022 at 09:22:26AM +0100, Marc Zyngier wrote: > On Tue, 05 Jul 2022 14:52:43 +0100, > Serge Semin wrote: > > > > Hi Samuel > > > > On Fri, Jul 01, 2022 at 03:00:49PM -0500, Samuel Holland wrote: > > > The MIPS GIC irqchip driver may be selected in a uniprocessor > > > configuration, but it unconditionally registers an IPI domain. > > > > > > Limit the part of the driver dealing with IPIs to only be compiled when > > > GENERIC_IRQ_IPI is enabled, which corresponds to an SMP configuration. > > > > Thanks for the patch. Some comment is below. > > > > > > > > Reported-by: kernel test robot > > > Signed-off-by: Samuel Holland > > > --- > > > > > > Changes in v3: > > > - New patch to fix build errors in uniprocessor MIPS configs > > > > > > drivers/irqchip/Kconfig | 3 +- > > > drivers/irqchip/irq-mips-gic.c | 80 +++++++++++++++++++++++----------- > > > 2 files changed, 56 insertions(+), 27 deletions(-) > > > > > > diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig > > > index 1f23a6be7d88..d26a4ff7c99f 100644 > > > --- a/drivers/irqchip/Kconfig > > > +++ b/drivers/irqchip/Kconfig > > > @@ -322,7 +322,8 @@ config KEYSTONE_IRQ > > > > > > config MIPS_GIC > > > bool > > > - select GENERIC_IRQ_IPI > > > + select GENERIC_IRQ_IPI if SMP > > > > > + select IRQ_DOMAIN_HIERARCHY > > > > It seems to me that the IRQ domains hierarchy is supposed to be > > created only if IPI is required. At least that's what the MIPS GIC > > driver implies. Thus we can go further and CONFIG_IRQ_DOMAIN_HIERARCHY > > ifdef-out the gic_irq_domain_alloc() and gic_irq_domain_free() > > methods definition together with the initialization: > > > > static const struct irq_domain_ops gic_irq_domain_ops = { > > .xlate = gic_irq_domain_xlate, > > +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY > > .alloc = gic_irq_domain_alloc, > > .free = gic_irq_domain_free, > > +#endif > > .map = gic_irq_domain_map, > > }; > > > > If the GENERIC_IRQ_IPI config is enabled, CONFIG_IRQ_DOMAIN_HIERARCHY > > will be automatically selected (see the config definition in > > kernel/irq/Kconfig). If the IRQs hierarchy is needed for some another > > functionality like GENERIC_MSI_IRQ_DOMAIN or GPIOs then they will > > explicitly enable the IRQ_DOMAIN_HIERARCHY config thus activating the > > denoted .alloc and .free methods definitions. > > > > To sum up you can get rid of the IRQ_DOMAIN_HIERARCHY config > > force-select from this patch and make the MIPS GIC driver code a bit > > more coherent. > > > > @Marc, please correct me if were wrong. > > Either way probably works correctly, but Samuel's approach is more > readable IMO. It is far easier to reason about a high-level feature > (GENERIC_IRQ_IPI) than an implementation detail (IRQ_DOMAIN_HIERARCHY). > The main idea of my comment was to get rid of the forcible IRQ_DOMAIN_HIERARCHY config selection, because the basic part of the driver doesn't depends on the hierarchical IRQ-domains functionality. It's needed only for IPIs and implicitly for the lower level IRQ device drivers like GPIO or PCIe-controllers, which explicitly enable the IRQ_DOMAIN_HIERARCHY config anyway. That's why instead of forcible IRQ_DOMAIN_HIERARCHY config selection (see Samuel patch) I suggested to make the corresponding functionality defined under the IRQ_DOMAIN_HIERARCHY config ifdefs, thus having the driver capable of creating the hierarchical IRQs domains only if it's required. > If you really want to save a handful of bytes, you can make the > callbacks conditional on GENERIC_IRQ_IPI, and be done with it. AFAIU I can't in this case. It must be either IRQ_DOMAIN_HIERARCHY ifdefs or explicit IRQ_DOMAIN_HIERARCHY select. There can be non-SMP (UP) systems with no need in IPIs but for instance having a GPIO or PCIe controller which require the hierarchical IRQ-domains support of the parental IRQ controller. So making the callbacks definition depended on the GENERIC_IRQ_IPI config state will break the driver for these systems. That's why I suggested to use CONFIG_IRQ_DOMAIN_HIERARCHY which activates the hierarchical IRQ domains support in the IRQ-chip system (see the irq_domain_ops structure conditional fields definition) and shall we have the suggested approach implemented in the MIPS GIC driver. -Sergey > But this can come as an additional patch. > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible.