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 7144AC4167B for ; Thu, 7 Dec 2023 09:44:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378708AbjLGJoI (ORCPT ); Thu, 7 Dec 2023 04:44:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378654AbjLGJoF (ORCPT ); Thu, 7 Dec 2023 04:44:05 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE845DD for ; Thu, 7 Dec 2023 01:44:11 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78B62C433C7; Thu, 7 Dec 2023 09:44:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701942251; bh=z9LEnc9SGPP1cSw8n0MwiUc7iERA9aZU0X4XLc/JCus=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qZ0oyfP6rihYVRM820jd+i9VgQtmywGaPXq7igsGv32dxX/J3EeENhsGVzajAtiDQ S2yY1ariJG0saxlG3+i+48dvm5AOYb6yFJPZEDHFY+gGdd/jjbLrO98YUoU8qaRdvv 3Be5rbRpPbKY+ucecdTPuNpO3eyvZIN8n/4Ip3ldpNjb3LJzdLdimrec2HA2++wehz z7IJBBG5+sWZX8HD0vjIgKfa1eyr3ZBzvDIGVWe9spjwxI0QOXs90zGv6n/Vm4czGu 1wE9XA+hc1u2c4/7b0BWBth0NB76ZJFrIWRRSjdMemgW5OqUFurE6Y6fDJCy8B+Xar JOYxApp7CccNw== Date: Thu, 7 Dec 2023 15:13:57 +0530 From: Manivannan Sadhasivam To: Bart Van Assche Cc: Naresh Maramaina , "James E.J. Bottomley" , "Martin K. Petersen" , Peter Wang , Andy Gross , Bjorn Andersson , Konrad Dybcio , Matthias Brugger , AngeloGioacchino Del Regno , chu.stanley@gmail.com, Alim Akhtar , Avri Altman , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, quic_cang@quicinc.com, quic_nguyenb@quicinc.com, Nitin Rawat Subject: Re: [PATCH V2 1/3] ufs: core: Add CPU latency QoS support for ufs driver Message-ID: <20231207094357.GI2932@thinkpad> References: <20231204143101.64163-1-quic_mnaresh@quicinc.com> <20231204143101.64163-2-quic_mnaresh@quicinc.com> <590ade27-b4da-49be-933b-e9959aa0cd4c@acm.org> <692cd503-5b14-4be6-831d-d8e9c282a95e@quicinc.com> <5e7c5c75-cb5f-4afe-9d57-b0cab01a6f26@acm.org> <20231206153242.GI12802@thinkpad> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 06, 2023 at 03:02:04PM -1000, Bart Van Assche wrote: > On 12/6/23 05:32, Manivannan Sadhasivam wrote: > > On Wed, Dec 06, 2023 at 07:32:54PM +0530, Naresh Maramaina wrote: > > > On 12/5/2023 10:41 PM, Bart Van Assche wrote: > > > > On 12/4/23 21:58, Naresh Maramaina wrote: > > > > > On 12/5/2023 12:30 AM, Bart Van Assche wrote: > > > > > > On 12/4/23 06:30, Maramaina Naresh wrote: > > > > > > > +    /* This capability allows the host controller driver to > > > > > > > use the PM QoS > > > > > > > +     * feature. > > > > > > > +     */ > > > > > > > +    UFSHCD_CAP_PM_QOS                = 1 << 13, > > > > > > >   }; > > > > > > > > > > > > Why does it depend on the host driver whether or not PM QoS is > > > > > > enabled? Why isn't it enabled unconditionally? > > > > > > > > > > For some platform vendors power KPI might be more important than > > > > > random io KPI. Hence this flag is disabled by default and can be > > > > > enabled based on platform requirement. > > > > > > > > How about leaving this flag out unless if a host vendor asks explicitly > > > > for this flag? > > > > > > IMHO, instead of completely removing this flag, how about having > > > flag like "UFSHCD_CAP_DISABLE_PM_QOS" which will make PMQOS enable > > > by default and if some host vendor wants to disable it explicitly, > > > they can enable that flag. > > > Please let me know your opinion. > > That would result in a flag that is tested but that is never set by > upstream code. I'm not sure that's acceptable. > Agree. The flag shouldn't be introduced if there are no users. > > If a vendor wants to disable this feature, then the driver has to be modified. > > That won't be very convenient. So either this has to be configured through sysfs > > or Kconfig if flexibility matters. > > Kconfig sounds worse to me because changing any Kconfig flag requires a > modification of the Android GKI kernel. > Hmm, ok. Then I think we can have a sysfs hook to toggle the enable switch. - Mani > Thanks, > > Bart. -- மணிவண்ணன் சதாசிவம்