Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755029AbaFQHpd (ORCPT ); Tue, 17 Jun 2014 03:45:33 -0400 Received: from mail-qa0-f49.google.com ([209.85.216.49]:43678 "EHLO mail-qa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752816AbaFQHpb (ORCPT ); Tue, 17 Jun 2014 03:45:31 -0400 MIME-Version: 1.0 In-Reply-To: <539F9412.3010209@realsil.com.cn> References: <7b58fb0b0915ea0b0838404c74ec22a3b6e5f5a8.1402037565.git.micky_ching@realsil.com.cn> <539EB43B.8070707@realsil.com.cn> <539F9412.3010209@realsil.com.cn> Date: Tue, 17 Jun 2014 09:45:31 +0200 Message-ID: Subject: Re: [PATCH 2/2] mmc: rtsx: add support for async request From: Ulf Hansson To: micky Cc: Samuel Ortiz , Lee Jones , Chris Ball , devel@linuxdriverproject.org, "linux-kernel@vger.kernel.org" , linux-mmc , Greg Kroah-Hartman , Dan Carpenter , Roger , Wei WANG Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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(), . 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/