Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756454AbaFRBNL (ORCPT ); Tue, 17 Jun 2014 21:13:11 -0400 Received: from rtits2.realtek.com ([60.250.210.242]:43645 "EHLO rtits2.realtek.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755054AbaFRBNI (ORCPT ); Tue, 17 Jun 2014 21:13:08 -0400 X-SpamFilter-By: BOX Solutions SpamTrap 5.39 with qID s5I1CRrX025598, This message is accepted by code: ctloc85258 Message-ID: <53A0E89F.9010006@realsil.com.cn> Date: Wed, 18 Jun 2014 09:17:19 +0800 From: micky User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Ulf Hansson CC: Samuel Ortiz , Lee Jones , Chris Ball , , "linux-kernel@vger.kernel.org" , linux-mmc , Greg Kroah-Hartman , Dan Carpenter , Roger , Wei WANG Subject: Re: [PATCH 2/2] mmc: rtsx: add support for async request References: <7b58fb0b0915ea0b0838404c74ec22a3b6e5f5a8.1402037565.git.micky_ching@realsil.com.cn> <539EB43B.8070707@realsil.com.cn> <539F9412.3010209@realsil.com.cn> In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [172.29.41.103] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/17/2014 03:45 PM, Ulf Hansson wrote: > On 17 June 2014 03:04, micky wrote: >> On 06/16/2014 08:40 PM, Ulf Hansson wrote: >>> On 16 June 2014 11:09, micky wrote: >>>> On 06/16/2014 04:42 PM, Ulf Hansson wrote: >>>>>> @@ -36,7 +37,10 @@ struct realtek_pci_sdmmc { >>>>>>> struct rtsx_pcr *pcr; >>>>>>> struct mmc_host *mmc; >>>>>>> struct mmc_request *mrq; >>>>>>> + struct workqueue_struct *workq; >>>>>>> +#define SDMMC_WORKQ_NAME "rtsx_pci_sdmmc_workq" >>>>>>> >>>>>>> + struct work_struct work; >>>>> I am trying to understand why you need a work/workqueue to implement >>>>> this feature. Is that really the case? >>>>> >>>>> Could you elaborate on the reasons? >>>> Hi Uffe, >>>> >>>> we need return as fast as possible in mmc_host_ops request(ops->request) >>>> callback, >>>> so the mmc core can continue handle next request. >>>> when next request everything is ready, it will wait previous done(if not >>>> done), >>>> then call ops->request(). >>>> >>>> we can't use atomic context, because we use mutex_lock() to protect >>> ops->request should never executed in atomic context. Is that your >>> concern? >> Yes. > Okay. Unless I missed your point, I don't think you need the work/workqueue. any other method? > > Because, ops->request isn't ever executed in atomic context. That's > due to the mmc core, which handles the async mechanism, are waiting > for a completion variable in process context, before it invokes the > ops->request() callback. > > That completion variable will be kicked, from your host driver, when > you invoke mmc_request_done(), . Sorry, I don't understand here, how kicked? I think the flow is: - not wait for first req - init mrq->done - ops->request() --- A.rtsx: start queue work. - continue fetch next req - prepare next req ok, - wait previous done. --- B.(mmc_request_done() may be called at any time from A to B) - init mrq->done - ops->request() --- C.rtsx: start queue next work. ... and seems no problem. Best Regards. micky. > Kind regards > Uffe > >>> >>>> resource, and we have to hold the lock during handle request. >>>> So I use workq, we just queue a work and return in ops->request(), >>>> The mmc core can continue without blocking at ops->request(). >>>> >>>> Best Regards. >>>> micky. >>> Kind regards >>> Uffe >>> . >>> > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/