From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeffrey Hugo Subject: Re: [PATCH] ACPI/PPTT: Handle architecturally unknown cache types Date: Wed, 12 Sep 2018 10:06:49 -0600 Message-ID: References: <1536694334-5811-1-git-send-email-jhugo@codeaurora.org> <98e2e6fa-7256-b5ac-7d2e-42c858c6e57c@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Jeremy Linton , rjw@rjwysocki.net, linux-acpi@vger.kernel.org Cc: linux-kernel@vger.kernel.org, vkilari@codeaurora.org, Sudeep Holla List-Id: linux-acpi@vger.kernel.org On 9/12/2018 9:39 AM, Jeremy Linton wrote: > Hi, > > > On 09/12/2018 09:41 AM, Jeffrey Hugo wrote: >> The HW designers have indicated that there is no sane way to provide >> sets/ways information to software, even on an informational basis (ie >> not for cache maintenance, but for performance optimizations). >> Therefore the firmware will not provide this information because it >> will be wrong. >> >> So, therefore, we should still be able to tell the user that a cache >> exists at the relevant level, and what size it is.  On the concerned >> system, we cannot do that currently. > > Ok, so set the fields to zero in firmware node, and mark them valid. Is that what the PPTT spec says to do? > That logically says that there isn't any set/way information for the > cache (which implies direct mapped). Making inferences such as that have gotten folks into trouble when interpreting other specs. Unfortunately I am not allowed to detail more about this specific system, however implying that the affected cache(s) are direct mapped is incorrect. Officially, what you have is a cache or multiple caches at certain levels that have a specified size. You can make no inferences about the exact behavior or implementation of the cache beyond what FW explicitly provides. I'm not particularly a fan of it, but its what I have to deal with. -- Jeffrey Hugo Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.