From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f171.google.com (mail-pf1-f171.google.com [209.85.210.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAA23EE; Wed, 6 Dec 2023 17:02:10 -0800 (PST) Received: by mail-pf1-f171.google.com with SMTP id d2e1a72fcca58-6ce6dd83945so114584b3a.3; Wed, 06 Dec 2023 17:02:10 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701910930; x=1702515730; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=hsY9pw0TDst5fn7pyaJpwFYHQHsp2P8sIo6DgROWKDI=; b=flfmmCKko9MjYEAXqz8N4rr30vWeSv0cPcBgzzjh2IsIZpx/uE2colbPUaQfPjOwtx v8FCnfBFOk9NFcKRLHWY3eJSPd9ZHbVIxl1li3PlwjZNbABmH7CvCmZEXA2/cEjF+FBx EzxeyDG0db64mhNweXW4DNxXRT5A/mnrrCDmNhwKsAMP839h6cAvN35EF9mQmf2jV7S0 i0iMK5kBhMkS8/41NCI0KKy9OW4EiYOoFWpR53lEYEYmM8gb/C77eYCVKBInDPy1MNHd JVQWl3W2CDR9C4FWd7zI8pMuupimVS+iieFL6QLdrvtYNLsE104+OQb2eLOYLY0dMhHh zFAg== X-Gm-Message-State: AOJu0Ywd892/Pq4IcvU/z6a0PAbJHL100pLT0tBDtoL5S+01RvPxqWbT auePmjotkWlSlSl1jTkMsfM= X-Google-Smtp-Source: AGHT+IHMqy62pr33s+axRTNU9zRKI+eQxYUdPtYiMKmdFwxGEZ5YOdCxe0OaOGpyoMV2n57/gKS5ZA== X-Received: by 2002:a05:6a20:43a7:b0:18f:bf91:2938 with SMTP id i39-20020a056a2043a700b0018fbf912938mr2423155pzl.125.1701910930060; Wed, 06 Dec 2023 17:02:10 -0800 (PST) Received: from [172.20.2.177] (rrcs-173-197-90-226.west.biz.rr.com. [173.197.90.226]) by smtp.gmail.com with ESMTPSA id p2-20020aa78602000000b006889511ab14sm134543pfn.37.2023.12.06.17.02.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 06 Dec 2023 17:02:08 -0800 (PST) Message-ID: Date: Wed, 6 Dec 2023 15:02:04 -1000 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2 1/3] ufs: core: Add CPU latency QoS support for ufs driver Content-Language: en-US To: Manivannan Sadhasivam , Naresh Maramaina Cc: "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 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> From: Bart Van Assche In-Reply-To: <20231206153242.GI12802@thinkpad> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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. > 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. Thanks, Bart.