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 B4B6EC4167B for ; Thu, 7 Dec 2023 11:21:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378983AbjLGLVL (ORCPT ); Thu, 7 Dec 2023 06:21:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378921AbjLGLVI (ORCPT ); Thu, 7 Dec 2023 06:21:08 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF716FA for ; Thu, 7 Dec 2023 03:21:14 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F956C433C7; Thu, 7 Dec 2023 11:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701948074; bh=Y+kCs8J8Xte1h+4V1sfgYUbvivj8bv1hTvD8IuIDh+U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=d+gqu0HgAAr0TvC+OmZqlvMV+esi/bBl1U5DBLY5pEgyEhigN3qu5ic0LOFs8xGEW GjubXsS26m3+ZXhanUEOi2q0MuSBCYCOSbgTxODrwr8cEHPIh7Dl7EJGsXDiMj0U+W iKGzC2sbvJPXnJaWKM0Mw05vxO1S25jFERAWaJLB9M4IxPdzoOmgJgzGv6eeQS7RCx frIuj2vmZ3/ydvd3y0ZvUX3oq6V6IBi0iMlKlfSAFKt+btXI6e+4hZCySzkCAV8nqS mkiMIwUtlNdxgDalgPhnuXbOQgYZJFIEsTmWOHm/vHDlF5Er9OWLaoIZ1klFBqoeAg PM+kvTyiDB6HA== Date: Thu, 7 Dec 2023 16:51:01 +0530 From: Manivannan Sadhasivam To: Nitin Rawat Cc: Manivannan Sadhasivam , Bart Van Assche , 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 Subject: Re: [PATCH V2 1/3] ufs: core: Add CPU latency QoS support for ufs driver Message-ID: <20231207112101.GK2932@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> <20231207094357.GI2932@thinkpad> <286b6f8a-c634-19ed-cf53-276cfe05d03f@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <286b6f8a-c634-19ed-cf53-276cfe05d03f@quicinc.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 07, 2023 at 03:56:43PM +0530, Nitin Rawat wrote: > > > On 12/7/2023 3:13 PM, Manivannan Sadhasivam wrote: > > 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. > > Hi Bart, Mani > > How about keeping this feature enabled by default and having a module > parameter to disable pmqos feature if required ? > Module params not encouraged these days unless there are no other feasible options available. - Mani > Regards, > Nitin > > > > > - Mani > > > > > Thanks, > > > > > > Bart. > > > -- மணிவண்ணன் சதாசிவம்