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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 798F0F9D0CB for ; Tue, 14 Apr 2026 12:26:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uproPa0wovE0vExP1gpIIrYvV3qSxZqfdZRO8Daxj94=; b=2KJNvC7qTnsGJOz0/8rWYBm+6H tHNGddJtwtpFz159GQZb2XZh86oyFE2iS1mRTdCNsN2WZeTo8YZV73kuGiybJYL7OSMr28C5lCEEM 6z6lcfcvrAp+4XePeZGAKAepOEyNyOOxa511mzhW3JR4K/wOOeuDHP8DOKGpkGelYvNqhi1N75T4P TFQTNQpdzMdVc/9rEj+ENjtUxBZbc58G1ecCQyb/LPipl2TzbzTEmyZzcKv1vI/IYbZnxLAts842S id9rWHutCh5qat/t8gGDfvGwWzA6JdCi5QU8A7nU5IHi6T5DIPFHou7ls486MmwwKKrZOmpzQKlFI g91oZuGw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wCcq9-0000000HIIZ-0Wj1; Tue, 14 Apr 2026 12:26:01 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wCcq8-0000000HIIT-0pax for linux-arm-kernel@lists.infradead.org; Tue, 14 Apr 2026 12:26:00 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1D74560130; Tue, 14 Apr 2026 12:25:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DFCFC19425; Tue, 14 Apr 2026 12:25:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776169558; bh=0mxqJDlo804wnC50q8gJO4xhJeZDLM0HfNEaZTltFmQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=peOoUo+2oGBuWmDUjhvX9j/hAewpeDfH2u+jmtg9Dh71UufFfYnP+oXNdP8B243Ov mWZ5nU9nj6eGX/KYBtL0By0CKbVANPc/N14231R33UPx8OMAKbsSairbuhpDsMsXcq YArLLwOrd5COXe6TiDL5EaQFbr/CpJDQMEsiXFz4eWVLGxu2jHOKH1m7rH/VYZslim lYB/MuuzemJin6TsIlbbst0ypigj7vJzy2Y+3+INJdwgnrSKs8DQZyLX7nNWRhawID 5xcL0XphJ/tbYLYIwtCWUe+ni2O/2syednpzfAim22Y+OwLg6CPz8enh6GAmNq5WwF 02sQK1XTaHRVg== Date: Tue, 14 Apr 2026 13:25:53 +0100 From: Sudeep Holla To: "lihuisong (C)" Cc: Breno Leitao , Sudeep Holla , "Rafael J. Wysocki" , Len Brown , lpieralisi@kernel.org, catalin.marinas@arm.com, will@kernel.org, "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, pjaroszynski@nvidia.com, guohanjun@huawei.com, linux-arm-kernel@lists.infradead.org, rmikey@meta.com, kernel-team@meta.com Subject: Re: [PATCH RFC] ACPI: processor: idle: Do not propagate acpi_processor_ffh_lpi_probe() -ENODEV Message-ID: <20260414-cute-shapeless-dolphin-c5b2fc@sudeepholla> References: <20260413-ffh-v1-1-301704f69e2f@debian.org> <6694ca7c-13bf-4e7d-9621-bc992cbf96a7@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6694ca7c-13bf-4e7d-9621-bc992cbf96a7@huawei.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 14, 2026 at 07:31:29PM +0800, lihuisong (C) wrote: > > On 4/14/2026 6:21 PM, Breno Leitao wrote: > > Hello Huisong, > > > > On Tue, Apr 14, 2026 at 05:43:51PM +0800, lihuisong (C) wrote: > > > But it is a real issue. Thanks for your report. > > > I think the best way to fix your issue is that remove this verification in > > > psci_acpi_cpu_init_idle(). > > > Because it is legal for platform to report one LPI state. > > > This function just needs to verify the LPI states which are FFH. > > Thank you for the prompt feedback. > > > > Would this approach work? > > > > commit 6c9d52840a4f778cc989838ba76ee51416e85de3 > > Author: Breno Leitao > > Date: Tue Apr 14 03:16:08 2026 -0700 > > > > ACPI: processor: idle: Allow platforms with only one LPI state > > psci_acpi_cpu_init_idle() rejects platforms where power.count - 1 <= 0 > > by returning -ENODEV. However, having a single LPI state (WFI) is a > > valid configuration. The function's purpose is to verify FFH idle states, > > and when count is zero, there are simply no FFH states to validate — > > this is not an error. > > On NVIDIA Grace (aarch64) systems with PSCIv1.1, power.count is 1 for > > all 72 CPUs, so the probe fails with -ENODEV. After commit cac173bea57d > > ("ACPI: processor: idle: Rework the handling of > > acpi_processor_ffh_lpi_probe()"), this failure propagates up and prevents > > cpuidle registration entirely. > > Change the check from (count <= 0) to (count < 0) so that platforms > > with only WFI are accepted. The for loop naturally handles count == 0 > > by not iterating. > > Fixes: cac173bea57d ("ACPI: processor: idle: Rework the handling of acpi_processor_ffh_lpi_probe()") > > Signed-off-by: Breno Leitao > > > > diff --git a/drivers/acpi/arm64/cpuidle.c b/drivers/acpi/arm64/cpuidle.c > > index 801f9c4501425..7791b751042ce 100644 > > --- a/drivers/acpi/arm64/cpuidle.c > > +++ b/drivers/acpi/arm64/cpuidle.c > > @@ -31,7 +31,7 @@ static int psci_acpi_cpu_init_idle(unsigned int cpu) > > return -EOPNOTSUPP; > > count = pr->power.count - 1; > > - if (count <= 0) > > + if (count < 0) > > return -ENODEV; > > for (i = 0; i < count; i++) { > > This count already verified in acpi_processor_get_lpi_info. > > I suggest modifing it as below: > > --> > > git diff > diff --git a/drivers/acpi/arm64/cpuidle.c b/drivers/acpi/arm64/cpuidle.c > index 801f9c450142..c68a5db8ebba 100644 > --- a/drivers/acpi/arm64/cpuidle.c > +++ b/drivers/acpi/arm64/cpuidle.c > @@ -16,7 +16,7 @@ > >  static int psci_acpi_cpu_init_idle(unsigned int cpu) >  { > -       int i, count; > +       int i; >         struct acpi_lpi_state *lpi; >         struct acpi_processor *pr = per_cpu(processors, cpu); > > @@ -30,14 +30,10 @@ static int psci_acpi_cpu_init_idle(unsigned int cpu) >         if (!psci_ops.cpu_suspend) >                 return -EOPNOTSUPP; > > -       count = pr->power.count - 1; > -       if (count <= 0) > -               return -ENODEV; > - It was intentionally designed this way, as there is little value in defining only WFI in the _LPI tables. In the absence of a cpuidle driver/LPI entry, arch_cpu_idle() is invoked, which is sufficient and avoids unnecessary complexity, only to ultimately execute wfi() anyway. So while I understand that the kernel did not report an error previously, that does not mean the _LPI table is merely moot on this platform when it contains only a WFI state. -- Regards, Sudeep