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 8E6D2CA101F for ; Wed, 10 Sep 2025 19:20:00 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/dGngHXEurLSbEzxRGWI9S+2bpiLhPxw3hCSQE6Fz1c=; b=l7PYKdXXIenQSW0N7CEHnJZar8 p3WpjuILUjdiEzV899F8HPvhDgF9Dc/vISvxh8bR2UdfYo4fGgMg9jasZNlVklJ43OM2VdkWTNSFL 5gdNt+1idm6bUO9mUYkfasg0KnaCOM7iqpzGiyljqV2jCsuYdVgRy5vs70GAKGRc4BQMrjze6e6j5 17PjvnWRlZ20J+2bJCVphhvLaYUkA5Y4wtaNSDs82n/3ee8ixU3fecA8tBZ8taSDmUxhP+iCMt/Tj Ov4K1VeWUdxxDym/tN6kFruOprxx8pkj730rrHY9o8Gv5VlV09ZlM1w9zyo1fVqlwwY34PG2bkMfE 9F9dgwFw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwQME-0000000GEar-1opF; Wed, 10 Sep 2025 19:19:54 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwQMB-0000000GEYC-08Da for linux-arm-kernel@lists.infradead.org; Wed, 10 Sep 2025 19:19:52 +0000 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 EBEDE16F2; Wed, 10 Sep 2025 12:19:38 -0700 (PDT) Received: from [10.1.197.69] (eglon.cambridge.arm.com [10.1.197.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 99F3B3F694; Wed, 10 Sep 2025 12:19:41 -0700 (PDT) Message-ID: Date: Wed, 10 Sep 2025 20:19:41 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/33] ACPI / PPTT: Stop acpi_count_levels() expecting callers to clear levels To: Lorenzo Pieralisi Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org, devicetree@vger.kernel.org, shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Rex Nie , Dave Martin , Koba Ko , Shanker Donthineni , fenghuay@nvidia.com, baisheng.gao@unisoc.com, Jonathan Cameron , Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Hanjun Guo , Sudeep Holla , Krzysztof Kozlowski , Conor Dooley , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich References: <20250822153048.2287-1-james.morse@arm.com> <20250822153048.2287-39-james.morse@arm.com> Content-Language: en-GB From: James Morse In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250910_121951_482499_A92B79D2 X-CRM114-Status: GOOD ( 19.22 ) 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 Hi Lorenzo, On 10/09/2025 14:44, Lorenzo Pieralisi wrote: > On Fri, Aug 22, 2025 at 03:30:19PM +0000, James Morse wrote: >> acpi_count_levels() passes the number of levels back via a pointer argument. >> It also passes this to acpi_find_cache_level() as the starting_level, and >> preserves this value as it walks up the cpu_node tree counting the levels. >> >> This means the caller must initialise 'levels' due to acpi_count_levels() >> internals. The only caller acpi_get_cache_info() happens to have already >> initialised levels to zero, which acpi_count_levels() depends on to get the >> correct result. >> >> Two results are passed back from acpi_count_levels(), unlike split_levels, >> levels is not optional. >> >> Split these two results up. The mandatory 'levels' is always returned, >> which hides the internal details from the caller, and avoids having >> duplicated initialisation in all callers. split_levels remains an >> optional argument passed back. >> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c >> index 4791ca2bdfac..8f9b9508acba 100644 >> --- a/drivers/acpi/pptt.c >> +++ b/drivers/acpi/pptt.c >> @@ -181,10 +181,10 @@ acpi_find_cache_level(struct acpi_table_header *table_hdr, >> * levels and split cache levels (data/instruction). >> * @table_hdr: Pointer to the head of the PPTT table >> * @cpu_node: processor node we wish to count caches for >> - * @levels: Number of levels if success. >> * @split_levels: Number of split cache levels (data/instruction) if >> - * success. Can by NULL. >> + * success. Can be NULL. > > Nit: tempting but this change does not belong here. Clearly a much loved typo! >> @@ -192,14 +192,18 @@ acpi_find_cache_level(struct acpi_table_header *table_hdr, >> * split cache levels (data/instruction) that exist at each level on the way >> * up. >> */ >> -static void acpi_count_levels(struct acpi_table_header *table_hdr, >> - struct acpi_pptt_processor *cpu_node, >> - unsigned int *levels, unsigned int *split_levels) >> +static int acpi_count_levels(struct acpi_table_header *table_hdr, >> + struct acpi_pptt_processor *cpu_node, >> + unsigned int *split_levels) >> { >> + int starting_level = 0; >> + >> do { >> - acpi_find_cache_level(table_hdr, cpu_node, levels, split_levels, 0, 0); >> + acpi_find_cache_level(table_hdr, cpu_node, &starting_level, split_levels, 0, 0); >> cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent); >> } while (cpu_node); >> + >> + return starting_level; >> } >> >> /** >> @@ -731,7 +735,7 @@ int acpi_get_cache_info(unsigned int cpu, unsigned int *levels, >> if (!cpu_node) >> return -ENOENT; >> >> - acpi_count_levels(table, cpu_node, levels, split_levels); >> + *levels = acpi_count_levels(table, cpu_node, split_levels); > Looks fine to me - though initializing > > *levels = 0 > > upper in the function now becomes superfluous (?) (well, it initializes > *levels to 0 if an error path is hit but on that case the caller should > not expect *levels to be initialized to anything IIUC). Maybe, but its the least surprising thing to do - hence the existing early clobber. > Apart from these (very) minor things: > > Reviewed-by: Lorenzo Pieralisi Thanks! James