From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adrian Hunter Subject: Re: [PATCH RFC] scsi: ufs: Disable blk-mq for now Date: Fri, 14 Sep 2018 16:03:25 +0300 Message-ID: References: <20180913112848.7807-1-adrian.hunter@intel.com> <20180913120459.GA4965@ming.t460p> <20180914015237.GC11059@ming.t460p> <2fdfc038-5b86-243c-9b0a-f294d281e5c0@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2fdfc038-5b86-243c-9b0a-f294d281e5c0@intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Ming Lei Cc: "Martin K . Petersen" , "James E . J . Bottomley" , Jens Axboe , Christoph Hellwig , Johannes Thumshirn , Bart Van Assche , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Stanislav Nijnikov , Evan Green , Vinayak Holikatti , Janek Kotas , Vivek Gautam , Asutosh Das , Subhash Jadavani , Sayali Lokhande , Li Wei , Bjorn Andersson , Jaegeuk Kim List-Id: linux-scsi@vger.kernel.org On 14/09/18 09:17, Adrian Hunter wrote: > On 14/09/18 04:52, Ming Lei wrote: >> On Thu, Sep 13, 2018 at 03:15:39PM +0300, Adrian Hunter wrote: >>> On 13/09/18 15:05, Ming Lei wrote: >>>> On Thu, Sep 13, 2018 at 02:28:48PM +0300, Adrian Hunter wrote: >>>>> blk-mq does not support runtime pm, so disable blk-mq support for now. >>>> >>>> So could you describe a bit what the issue you are trying to fix? >>> >>> UFS is a low-power solution, so we must be able to runtime suspend. >>> >>>> >>>> This is host level runtime PM you are trying to address, and if blk-mq >>>> runtime isn't enabled, I guess the host won't be runtime suspended at all >>>> because some of its descendant are always active. >>>> >>>> So seems we need to do nothing for preventing the host controller from >>>> entering runtime suspend. >>> >>> We don't want to prevent the host controller from runtime suspending, quite >>> the opposite. >> >> OK, got it. >> >> However, in previous discussion, it is strongly objected to use >> per-driver/device .use_blk_mq switch, so not sure if this way can >> be accepted. > > It is only needed for 4.19 so far. Otherwise just revert d5038a13eca7 > ("scsi: core: switch to scsi-mq by default") > >> >> BTW, I just posted the runtime PM enablement patches[1] for blk-mq, >> and I verified that it works fine and passed blktests & xfstest & my >> other sanity tests, could you try it on UFS? >> >> [1] https://marc.info/?l=linux-block&m=153684095523409&w=2 > > I will give it a go. Yes it seemed to work fine for UFS Tested-by: Adrian Hunter > > Obviously, if those patches go in, we wouldn't need to disable blk-mq > anymore, but that isn't until 4.20 at least. >