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 8D287C4167B for ; Thu, 30 Nov 2023 16:26:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232198AbjK3QZz (ORCPT ); Thu, 30 Nov 2023 11:25:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345452AbjK3QZn (ORCPT ); Thu, 30 Nov 2023 11:25:43 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7C8EE198; Thu, 30 Nov 2023 08:25:49 -0800 (PST) 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 EACC81042; Thu, 30 Nov 2023 08:26:35 -0800 (PST) Received: from pluto (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 11E1B3F6C4; Thu, 30 Nov 2023 08:25:46 -0800 (PST) Date: Thu, 30 Nov 2023 16:25:44 +0000 From: Cristian Marussi To: Sudeep Holla Cc: Sibi Sankar , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, quic_mdtipton@quicinc.com, linux-arm-kernel@lists.infradead.org, quic_asartor@quicinc.com, quic_lingutla@quicinc.com Subject: Re: [PATCH 2/3] firmware: arm_scmi: Fix freq/power truncation in the perf protocol Message-ID: References: <20231129065748.19871-1-quic_sibis@quicinc.com> <20231129065748.19871-3-quic_sibis@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 30, 2023 at 01:56:56PM +0000, Sudeep Holla wrote: > On Thu, Nov 30, 2023 at 12:49:42PM +0000, Cristian Marussi wrote: > > On Thu, Nov 30, 2023 at 12:05:06PM +0000, Sudeep Holla wrote: > > > On Wed, Nov 29, 2023 at 12:27:47PM +0530, Sibi Sankar wrote: > > > > Fix frequency and power truncation seen in the performance protocol by > > > > casting it with the correct type. > > > > > > > > > > While I always remembered to handle this when reviewing the spec, seem to > > > have forgotten when it came to handling in the implementation :(. Thanks > > > for spotting this. > > > > > > However I don't like the ugly type casting. I think we can do better. Also > > > looking at the code around the recently added level index mode, I think we > > > can simplify things like below patch. > > > > > > Cristian, > > > What do you think ? > > > > > > > Hi > > > > the cleanup seems nice in general to compact the mult_factor multipliers > > in one place, and regarding addressing the problem of truncation without > > the need of the explicit casting, should not be enough to change to > > additionally also change mult_factor to be an u64 ? > > > > I started exactly with that, but when I completed the patch, there was no > explicit need for it, so dropped it again. I can bump mult_factor to be > u64 but do you see any other place that would need it apart from having > single statement that does multiplication and assignment ? I am exploiting > the conditional based on level_indexing_mode here but I agree it may help > in backporting if I make mult_factor u64. > Ah right freq *= dom->multi_fact; does the trick..but cannot this by itself (under unplausibl conds) overflow and does not fit into a u32 mult_factor ? dom_info->mult_factor = (dom_info->sustained_freq_khz * 1000UL) / dom_info->sustained_perf_level; Thanks, Cristian