From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 541AF2EE604 for ; Fri, 25 Jul 2025 17:08:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753463318; cv=none; b=oEhWu+5fcjq5NKOt1I71hk2+i9JuIgmIk39b+RIGi5MfZ1BreOEmkQRCbpT+06T4vgzc4U7ixbn5V6Z7/UxtgZN4ZS+oHHfcoFvdFySY74JdMx8QmC3UhA01g7fXH9IEW4cHYX7r5wbKYBGIoElWO6FkWH5HmMfIBTFTV+ktl00= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753463318; c=relaxed/simple; bh=Dg8EERLMA/G6FhA4fLtbjaMYqi1Ci3suh9nhzu97xiQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EuquTzKBKd2o1gSgDWcfzy9ePUTxXJ2Ej+iz9Wi7twPx72Km8qxd7f8jBxqVeeWLJNLVYCNwwhJd3OXPS7IRgyGsJ4IB0NiK8/ezxg4WBmSc1P+fwtCoqzTZ1zw1GZgxJZk4jLxOfc9P22Qc5bAhTSKVNw1tb71STZTr5wQLVYg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 A2A30176C; Fri, 25 Jul 2025 10:08:28 -0700 (PDT) Received: from [10.1.197.43] (eglon.cambridge.arm.com [10.1.197.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9B17A3F66E; Fri, 25 Jul 2025 10:08:32 -0700 (PDT) Message-ID: Date: Fri, 25 Jul 2025 18:08:31 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 04/36] cacheinfo: Expose the code to generate a cache-id from a device_node To: Ben Horgan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Rob Herring , Rohit Mathew , Shanker Donthineni , Zeng Heng , Lecopzer Chen , Carl Worth , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , 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 References: <20250711183648.30766-1-james.morse@arm.com> <20250711183648.30766-5-james.morse@arm.com> Content-Language: en-GB From: James Morse In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Ben, On 14/07/2025 12:40, Ben Horgan wrote: > On 7/11/25 19:36, James Morse wrote: >> The MPAM driver identifies caches by id for use with resctrl. It >> needs to know the cache-id when probe-ing, but the value isn't set >> in cacheinfo until device_initcall(). >> >> Expose the code that generates the cache-id. The parts of the MPAM >> driver that run early can use this to set up the resctrl structures >> before cacheinfo is ready in device_initcall(). >> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c >> index 613410705a47..0fdd6358ee73 100644 >> --- a/drivers/base/cacheinfo.c >> +++ b/drivers/base/cacheinfo.c >> @@ -207,8 +207,7 @@ static bool match_cache_node(struct device_node *cpu, >>   #define arch_compact_of_hwid(_x)    (_x) >>   #endif >>   -static void cache_of_set_id(struct cacheinfo *this_leaf, >> -                struct device_node *cache_node) >> +unsigned long cache_of_calculate_id(struct device_node *cache_node) >>   { >>       struct device_node *cpu; >>       u32 min_id = ~0; >> @@ -219,15 +218,23 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, >>           id = arch_compact_of_hwid(id); >>           if (FIELD_GET(GENMASK_ULL(63, 32), id)) { >>               of_node_put(cpu); >> -            return; >> +            return ~0UL; >>           } >>             if (match_cache_node(cpu, cache_node)) >>               min_id = min(min_id, id); >>       } >>   -    if (min_id != ~0) { >> -        this_leaf->id = min_id; >> +    return min_id; > Looks like some 32bit/64bit confusion. Don't we want to return ~0UL if min_id == ~0? Certainly some confusion - yup, because cache_of_calculate_id() needs to return something that is out of range and (u32)-1 might be valid... I think changing min_id to be defined as: | unsigned long min_id = ~0UL; fixes this - any trip round the loop that doesn't match anything will eventually return ~0UL. Thanks! - I always get the 'UL' suffixes wrong. James